MRC SEA FOR HYDROPOWER ON THE MEKONG MAINSTREAM IMPACTS ASSESSMENT
(Opportunities and Risks)
Discussion Draft
14 May 2010
The MRC SEA of Hydropower on the Mekong mainstream comprises 4 main phases: (i) scoping, (ii) baseline assessment, (iii) opportunities & risks assessment, and (iv) avoidance, enhancement and mitigation assessment.
This report formally concludes the impacts assessment phase of the SEA and documents the development opportunities and risks presented by the 12 LMB mainstream projects in the context of sustainable development of the Mekong River Basin.
Disclaimer
This document was prepared for the Mekong River Commission Secretariat (MRCS) by a consultant team engaged to facilitate preparation of a Strategic Environment Assessment (SEA) of proposals for mainstream dams in the Lower Mekong Basin.
While the SEA is undertaken in a collaborative process involving the MRC Secretariat, National Mekong Committees of the four countries as well as civil society, private sector and other stakeholders, this document was prepared by the SEA Consultant team to assist the Secretariat as part of the information gathering activity. The views, conclusions, and recommendations contained in the document are not to be taken to represent the views of the MRC. Any and all of the MRC views, conclusions, and recommendations will be set forth solely in the MRC reports.
This document incorporates impact analysis of issues raised in the consultation process as prepared by the consultant team and is to be considered a discussion draft only for the multi‐stakeholder Regional Workshop in May 2010 in Vientiane.
For further information on the MRC initiative on Sustainable Hydropower (ISH) and the implementation of the SEA of proposed mainstream developments can be found on the MRC website: http://www.mrcmekong.org/ish/ish.htm and http://www.mrcmekong.org/ish/SEA.htm
The following position on mainstream dams is provided on the MRC website in 2009.
MRC position on the proposed mainstream hydropower dams in the Lower Mekong Basin
More than eleven hydropower dams are currently being studied by private sector developers for the mainstream of the Mekong. The 1995 Mekong Agreement requires that such projects are discussed extensively among all four countries prior to any decision being taken. That discussion, facilitated by MRC, will consider the full range of social, environmental and cross‐sector development impacts within the Lower Mekong Basin. So far, none of the prospective developers have reached the stage of notification and prior consultation required under the Mekong Agreement. MRC has already carried out extensive studies on the consequences for fisheries and peoples livelihoods and this information is widely available, see for example report of an expert group meeting on dams and fisheries. MRC is undertaking a Strategic Environmental Assessment (SEA) of the proposed mainstream dams to provide a broader understanding of the opportunities and risks of such development. Dialogue on these planned projects with governments, civil society and the private sector is being facilitated by MRC and all comments received will be considered.
MRC SEA | IMPACTS ASSESSMENT REPORT | CONTENTS
About the MRC SEA of Hydropower on the Mekong mainstream
The Mekong River Commission (MRC) is an inter‐governmental river basin organization that provides the institutional framework to implement the 1995 Mekong Agreement. The Governments of Cambodia, Lao PDR, Thailand and Viet Nam signed the Agreement on the Cooperation for the Sustainable Development of the Mekong River Basin. They agreed on joint management of their shared water resources by cooperating in a constructive and mutually beneficial manner for sustainable development, utilization, conservation and management of the Mekong River Basin water and related resources.
Poverty alleviation as a contribution to the UN Millennium Development Goals is also a priority. The two upper states of the Mekong River Basin, the People's Republic of China and the Union of Myanmar, are dialogue partners to the MRC.
In a region undergoing rapid change and economic growth, the MRC considers the development of hydropower on the Mekong mainstream as one of the most important strategic issues facing the Lower Mekong region. Through the knowledge embedded in all MRC programs, the MRC is conducting this Strategic Environment Assessment (SEA) to assist Member states to work together and make the best decisions for the basin.
Twelve hydropower schemes have been proposed for the Lao, Lao‐Thai and Cambodian reaches of the Mekong mainstream. Implementation of any or all of the proposed mainstream projects in the Lower Mekong Basin (LMB) could have profound and wide‐ranging socio‐economic and environmental impacts in all four riparian countries.
This SEA seeks to identify the potential opportunities and risks, as well as contribution of these proposed projects to regional development, by assessing alternative mainstream Mekong hydropower development strategies. In particular the SEA focuses on regional distribution of costs and benefits with respect to economic development, social equity and environmental protection. As such, the SEA supports the wider Basin Development Planning (BDP) process by complementing the MRC Basin Development Plan (BDP) assessment of basin‐wide development scenarios with more in‐depth analysis of power related and cross‐ sector development opportunities and risks of the proposed mainstream projects in the lower Basin.
The SEA is being coordinated by MRC’s cross‐cutting MRC Initiative for Sustainable Hydropower (ISH) working with all MRC programmes. The SEA will directly enhance the baseline information and assessment framework for subsequent government review of project‐specific EIAs prepared by developers. It will also inform how the MRC can best enhance its support to Member Countries when the formal process under the 1995 Mekong Agreement for prior consultation on any individual mainstream proposal is triggered (i.e. the Procedures for Notification, Prior Consultation and Agreement or PNPCA). The SEA findings will also inform steps that MRC programmes may consider in the next MRC Strategic Plan Cycle (2011‐2015) to help address the knowledge gaps and the key areas of uncertainty and risk concerning proposed mainstream developments.
The SEA began in May 2009 and is scheduled to complete the final report and recommendations by mid‐ 2010. This document is one of a series of documents arising from an intensive program of consultations in the Lower Mekong Basin and detailed expert analysis of the issues associated with developing hydropower on the Mekong mainstream. The intention is to consolidate SEA activities and progressively make conclusions and outputs available for public and critical review, so that stakeholder engagement can contribute to the SEA in a meaningful way. A full list of documents is available on the MRC SEA website.
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CONTENTS
1 Introduction...... 5
2 Summary of Opportunities & Risks...... 10
3 Proposed LMB Mainstream Hydropower ...... 32
4 Energy & Power...... 43
5 Economic Systems ...... 57
6 Hydrology & Sediment...... 73
7 Terrestrial Ecosystems & Agriculture...... 99
8 Aquatic systems...... 125
9 Fisheries...... 153
10 Social systems...... 187
11 Climate Change...... 210
12 Annex...... 230
12.1 Reservoir inundation maps...... 230
12.2 Calculating the likelihood of extreme events with climate change...... 241
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1 INTRODUCTION
1.1 OVERVIEW
The SEA Impacts Assessment phase marks a critical point in the MRC SEA of hydropower on the Mekong mainstream. The impacts assessment phase spans two months from April – June 2010 culminating in the SEA Regional Impacts Assessment workshop (19‐20 May, Vientiane) and subsequent finalization of the impacts assessment paper. This draft presents the SEA team’s preliminary findings concerning the opportunities and risks associated with the 12 LMB mainstream projects.
The draft report is for critical review by all SEA stakeholders, including: (i) MRC bodies (ii) government agencies in the four LMB nations, (iii) hydropower developers and the private sector (ii) civil‐society organizations in the LMB and internationally (iv) Mekong riparian communities and the representatives and public interest groups, and (v) donor partners and the finance community. The process of review, comment and then revision continues the consultative agenda of the SEA. The draft is being circulated for formal written submissions and placed online for wider exposure and responses. The main public forum for discussion on the draft is the SEA Regional Impacts Assessment Workshop.
The impact assessment is divided into the 8 strategic themes used throughout the SEA process including the baseline assessment phase, namely:
1. Energy & power
2. Economic systems
3. Hydrology & sediment
4. Terrestrial systems
5. Aquatic systems
6. Fisheries
7. Social systems
8. Climate change
The impacts assessment report will be finalized in early June 2010 in parallel with the preparation of the avoidance, enhancement and mitigation measures, which leads to a final regional workshop to consider the full SEA report.
1.2 ASSESSMENT APPROACH
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The assessment approach used in the SEA was described in the SEA Inception Report (IR) available online.1 It examines the mainstream projects from a number of geographic perspectives: regional, national, hydro‐ ecological zones and then in groupings to better explore the opportunities and risks associated with mainstream hydropower development.
REGIONAL: The Mekong River is commonly divided into its upper and lower reaches, based on arrangements for regional cooperation in sustainable development of the Mekong Basin. The SEA regional approach covers both, but focuses on transboundary concerns and the socio‐economic and natural system linkages between the LMB countries. MRC and under the 1995 Mekong Agreement provide the institutional and planning context at the regional level, especially (i) the Basin Development Plan (BDP), and (ii) the procedures for Prior Notification/ Prior Consultation Agreement (PNPCA).
NATIONAL: The LMB countries – Cambodia, Lao PDR, Thailand and Vietnam – and the effects of mainstream projects on each of their distinctive economies, and social and natural systems is the other key focus of the SEA. The SEA defined the key strategic issues of focus through an intensive program of ongoing national consultation. This means the 12 proposed projects are assessed against national interests and development priorities of the four LMB countries.
HYDRO‐ECOLOGICAL ZONES: The SEA impact assessment was further facilitated by viewing the projects within 6 hydro‐ecological zones of the Lower Mekong River. The zones have distinctive bio‐physical characteristics. They are defined based on: (i) hydrological regime, (ii) physiographic, (iii) land use, and (iv) existing, planned and potential resource developments (Table 1.1 and Figure 1.1).
Table 1.1: Hydrological spatial zoning for the Mekong Basin ZONE IBFM FLOW DESCRIPTION PHYSICAL FEATURES Mainstream ZONE projects 1 Lancang River • Major source is Tibetan plateau • Drainage: Parallel, • Existing, under with precipitation, snowmelt, no tributaries, construction and some glaciers in the reticular planned headwaters • Geology: Gorges, mainstream • Narrow steep gorges and bed‐ Ailao Shan Shear dams in China rock confined single thread Zone channel • Length ~1,900km • Zone of sediment production with a fall of ~4,200m 2 Chiang Saen to • Mountainous with large areas • Drainage: parallel Pak Beng, Vientiane of remaining forest • Geology: Gorges, Louangprabang • Steep narrow valleys with Wang Chao fault Xayaburi significant bed rock zone Pak Lay outcropping • Length ~1,100km Sanakham, • Significant meander in the with a fall of 200‐ • Pak Chom basin and within channel 300m features (islands, bars terraces) • Shared Lao‐Thai river bank • Zone of sediment production 3 Vientiane to • Increasing influence of • Drainage: dendritic Ban Koum Pakse tributaries to flow • Geology: Gorges, • Latsua • Predominantly alluvial reach central highlands & with widening cross‐section Khorat plateau and reduced meander • Length ~600km
1 www.mrcmekong.org/ish/SEA.htm
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• Large flat‐topped channel with a fall of 100‐ islands 200m • Shared Lao‐Thai river bank • Zone of sediment transport 4 Pakse to Kratie • 3S contributions (>25% of • Drainage: dendritic Latsua annual flow volume) • Geology: Gorges, (downstream) • Including wetlands of central highlands Don Sahong Simphandone, Khone Falls, • Length ~200‐ Thakho Stung Treng, Kratie 300km, with Stung Treng • Khone falls shifts river from negligible fall • Sambor braided channel system to floodplain • Mixed zone of sediment transport, production & deposition 5 Kratie to • Cambodian floodplain and the • Drainage and Phnom Penh Tonle Sap system dendritic form • Braided system of river • Length ~200‐ channels 300km, with • Overbank siltation maintain negligible fall flooding in the floodplain • Seasonal reversal of flow in the Tonle Sap system • Most inland extent of influence for saline intrusion and coastal process • Zone of sediment deposition 6 Phnom Penh • Braiding of the mainstream and • Drainage: to South China complex network of canals Distributaries Sea • Deltaic environment – river • Length ~100‐150km fans out into a network of with negligible fall distributaries • Extensive flooding and saline intrusion
Note: adapted from MRC, 2005; MRC, unpublished
GROUPING OF MAINSTREAM PROJECTS: The SEA adopts the MRC’s Basin Development Plan (BDP) scenario framework. The BDP 20‐year 2030 scenario and its two variants with/without the proposed LMB mainstream schemes is the basis for the SEA assessment of trends and impacts, also with reference to the baseline scenario. The baseline was the MRC Definite Future Scenario for 2015 (DFS). Both the DFS and PFS incorporate the influence of dams in the Lancang‐Mekong portion of the basin in China on the LMB.
The SEA also provides a “sensitivity analysis” which examined the LMB mainstream projects in three distinctive groups, namely the 20‐year 2030 scenario with only:
1. The proposed cascade of 6 mainstream dams upstream of Vientiane in Lao PDR 2. The proposed middle‐reach mainstream dams in Lao PDR, and 3. The proposed lower mainstream dams in Cambodia
Each thematic chapter presents the findings of the impact assessment (opportunities and risks) according to those various geographic levels of focus.
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Figure 1.1: Hydro‐ecological zones of the Mekong Basin: LMB mainstream projects are indicated as orange dots
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2 SUMMARY OF OPPORTUNITIES & RISKS
2.1 ENERGY AND POWER
Under the energy and power theme in the SEA baseline assessment, the motivations for hydropower development that are embodied in LMB country national power sector policies and regulatory systems were explored, along with country‐specific motivations for expanding cross‐border power trade (importers and exporters), and the nature of the bilateral and regional power trade agreements in place for that. The baseline assessment also looked closely the drivers and trends for electricity demand growth in the LMB where Thailand and Vietnam together represent 96% of demand, the progress and potential role of demand‐side management in reducing the rate of electricity demand growth, and the potential role of various conventional and alternative energy conversion technologies in the electricity supply mix, this with respect to the energy resource endowment in each LMB country and regionally.
The impact assessment for this theme focuses on the regional distribution of power benefits, as well as the impact of mainstream schemes on the power sectors in each LMB country as viewed from a utility economics perspective of power supply and least‐cost supply. The assessment is provided in mind of the scenarios used in the SEA assessment to integrate inputs from all the themes on the balance and distribution of opportunities and risks from proposed LMB mainstream dams.
The overall power benefits to LMB countries are significant. Table 2.1 shows the expectations with respect to the BDP 20‐yr probably future scenario (2030) with/ without LMB mainstream dams and the SEA sensitivity cases. The analysis shows the regional distribution of the annual electrical energy production, projected quantum of exports, gross power benefits, gross export revenue and net overall power benefit in economic terms. The difference in net overall economic power benefit between the 20‐ PFS with and without proposed LMB mainstream dams is about $US 3‐4 billion annually by 2030, (in discounted $US 2010). The economic power benefit depends on the future energy mix that is assumed. Over the longer term the greatest beneficiary is Lao PDR, in all cases.
Mainstream hydroelectric projects in Laos and Cambodia represent roughly two thirds of the total new energy potential of hydroelectric projects identified in the LMB (i.e. hydropower schemes not yet operating or undergoing firm development).
Power supply for LMB mainstream hydropower schemes is consistent with power sector policies of the LMB countries expressed in legislation and National Power Development Plans (PDPs). Among these factors include the potential contribution to:
Diversification of primary energy sources for power generation and supply source the largest power market at present (Thailand). Fuel diversification is a core element of Thailand PDPs, including the most recent draft PDP issued in January 2010 (see SEA baseline report).
Limiting the LMB region’s vulnerability to future international energy price volatility, steady and growing trend to import energy for power generation from outside the GMS (as discussed in the
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baseline report Thailand and Viet Nam expect the increase fossil fuel imports from outside the GMS). Cambodia’s situation as being almost wholly reliant on fossil import (diesel) is well known.
Bilateral MOUs to expand cross‐border power trade, which reflect LMB government agreement at present on the agreed quantum of power trade. It is important to note the current MOUs do not provide for all mainstream dams2
The objectives of the Greater Mekong Sub‐Region Intergovernmental Agreement on Power Interconnection and Trade3 in 2003 that seeks benefits in a number of areas including opportunities to enhance the reliability of supply, reduce investment and operating costs, and share in other benefits resulting from the interconnected operations of their systems.
Reinforce emission reduction strategies for the power sector at the regional level as discussed in section 7 (taking into account reservoir emissions).
From national power development perspective the development of mainstream proposal is most critical to the power sector development in Cambodia despite the fact that the energy from mainstream projects would be used regionally, and setting aside considerations of energy supply diversity (Thailand especially, and export earnings, Lao PDR and Cambodia).4
The Lao hydroelectric industry can develop tributary projects for domestic use and export can continue at a healthy pace without mainstream projects given the large inventory of economically attractive tributary projects in Laos. The potential scale of annual export earnings would be reduced. Other short and long term benefits would be forgone (e.g. for the short term, the ability to meet Lao demand growth in the next 25 years with a portion of the power from proposed LMB mainstream dams reserved for domestic supply (in the rage of 5‐10% to be negotiated) and in future when concession terms end.
The scale of electricity demand in Thailand and Vietnam and the cost of alternative forms of power supply (thermal) are such that development of LMB mainstream projects would have a minor impact on electricity prices in those power systems, and not radically alter the energy supply strategies of those countries applying least‐cost criteria alone.
2 See discussion in the SEA Baseline reports ( energy and power them in the summary and working paper Volume 2). 3 Includes the four MRC Member Countries plus Myanmar and southern China Provinces 4 Several circumstances determine that the two mainstream projects in Cambodia (Sambor and Stung Treng) are important to Cambodia’s power sector. Firstly, Cambodia has a very expensive generation system almost entirely dependent on imported oil. Thus, not only does Cambodia have to provide affordable power to meet incremental demand, but it also needs to replace its existing generation as much as possible. Secondly, Cambodia has a very small inventory of attractive tributary projects. The energy potential of these projects is not sufficient to meet incremental demands, let alone replace existing generation or export. Thirdly, Cambodia has no significant experience in hydroelectric development or operation and thus will rely much more than Laos on foreign partnerships, which can only be attracted by mainstream projects enabled by power exports.
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Table 2.1 Regional Distribution of LMB Power Benefits for the 20‐year Probable Future (with and without LMB mainstream dams) and sensitivity cases
LMB Regional POWER SUPPLY PR0JECTED POWER EXPORT PROJECT INVESTMENT Distribution (GWh/Year) (GWh/Year) ($USM)
SCENARIO1 CAM LAO THAI VIE TOTAL CAM LAO THAI VIE TOTAL CAM LAO THAI VIE TOTAL
2030‐20Y‐with MD 3,677 20,412 60,694 35,058 119,840 19,384 64,004 0 0 83,389 11,669 27,165 0 2,771 41,605 2030‐20Y‐w/o MD 1,703 9,038 26,206 16,346 53,293 1,618 28,571 0 0 30,189 1,268 11,857 0 2,771 15,896 2030‐20Y‐ MD in zone 2 only 1,703 12,287 50,558 21,240 85,787 1,618 57,816 0 0 59,434 1,268 22,031 0 2,771 26,070 2030‐20Y‐ zone 3 only 1,703 16,759 30,423 16,346 65,231 1,618 32,788 0 0 34,406 1,268 16,402 0 2,771 20,441 2030‐20Y‐ zone 4 only 3,677 9,441 32,126 30,164 75,408 19,384 30,542 0 0 49,927 11,669 12,447 0 2,771 26,886
LMB Regional GROSS BENEFIT OF SUPPLY GROSS EXPORT REVENUE NET OVERALL POWER BENEFIT Distribution ($USM/Year) Estimated ($USM/Year) ($USM/Year)
SCENARIO CAM LAO THAI VIE TOTAL CAM LAO THAI VIE TOTAL CAM LAO THAI VIE TOTAL
2030‐20Year with MD 782 3,555 5,284 2,559 12,179 1,250 4,676 0 0 5,926 722 5,272 832 834 7,659 2030‐20Y‐w/o MD 362 1,574 2,281 1,193 5,410 100 2,113 0 0 2,214 273 2,394 381 629 3,677 2030‐20Y‐ zone 2 only 362 2,140 4,401 1,550 8,453 100 4,219 0 0 4,319 273 3,958 699 682 5,613 2030‐20Y‐ zone 3 only 362 2,919 2,648 1,193 7,122 100 2,425 0 0 2,526 273 3,556 436 629 4,894 2030‐20Y‐ zone 4 only 782 1,644 2,797 2,201 7,424 1,250 2,259 0 0 3,509 722 2,546 459 780 4,506
Notes: 1 Scenarios are based on the MRC Basin Development Plan (BDP 20 year Probable Future ‐ 2030 snap shot) 2 Gross benefit of supply is based on avoided thermal costs in country where power is consumed
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2.2 ECONOMIC SYSTEMS
The development of proposed LMB mainstream dams would offer a range of economic opportunities for the regional power sector and provide synergy, or contribute to economic opportunity in other sectors of the economy, mostly navigation and irrigation development.
There will be a net economic benefit for the power sectors in all countries, as noted in the discussion on opportunities in the power sector (Table 2.1 previously)
The scale of proposed FDI in MSHP between 2010 and 2030 is huge and amounts to over USD 20 billion. This is likely to have significant economic impact as these investments stimulate employment, engineering industries and other suppliers of inputs to these projects. While some portion of this investment will inevitably be sourced from outside the host countries and the LMB, a significant portion is likely to be spent locally and regionally (Greater Mekong Sub‐region GMS).
There will be significant longer‐term opportunities for investment of export revenue earnings for the exporting countries, but these will be more limited at the start (during the 25‐year concession periods). The revenues can be applied to investment in national and local development and public services and poverty alleviation, though there is little information on the revenue flow over time and how revenues will be spent.5
Mainstream dams are also likely to have wide ranging economic impacts which are distributed unevenly across the LMB communities and LMB countries, and which differ considerably in their significance between different locations and groups. At the national level, the economic opportunities and risk vary between countries.
Macro economic impact concerns in smaller economies of host countries are also likely to result from i) the influx of investment capital and foreign exchange revenue due to mainstream hydropower development; and, ii) any increased levels of government debt needed to fund government equity stakes in these MSHP developments. The availability of concessionary finance may be more limited than what is available for tributary investment.
Macro economic impacts are likely to be of particular significance for Lao PDR due to their size relative to the rest of the economy.
The proposed mainstream projects are enclave projects (importing inputs and exporting outputs), and are therefore expected to source most inputs from outside the host countries to a larger extent in the greater Mekong Sub‐region (GMS).
Economic stimulus ‐ capital in‐flows and increased government spending funded by hydropower earnings revenues is likely to have a positive stimulus effect on the economy as a whole.
5 See discussion on impact on national economies related to concession periods. It is noted that experience in Lao PDR on exporting power from tributary projects that are private sector developed shows a next positive revenue flow to Government during the concession period (25 years).
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Booming sector effects These impacts of a booming hydropower sector and increased government expenditures will need to be managed very carefully by the government as they could lead to macro‐ economic imbalances, real exchange rate appreciation and thus have a negative economic impact on other sectors such as manufacturing and agriculture. Both sectors are important for poverty reduction.
Increased levels of host country debt ‐ Increased levels of government debt could pose a concern in the short to medium term to the extent that the power sector or national debt is incurred for government equity share in LMB schemes and the tradition sources of concessionary finance are not available to fund equity contributions. It is not clear whether the extra cost of debt‐service, and increased risk premiums on sovereign debt will be offset by increased revenues from these projects in the short term.
SECTOR IMPACTS
MSHP development is likely to imply increased opportunities across a number of sectors as well as risks. For example, while agricultural land will be lost in inundation areas there is likely to be an increase in irrigation and irrigated area which will improve overall agricultural productivity. Similarly, while capture fisheries is likely to decline significantly when all dams are pursued, impoundments will create new opportunities for the development of reservoir fisheries.
The nature of the opportunities and risks associated with key impacted sectors are given in the table 2.1 below. The final column gives an estimate on whether or not the balance of the opportunities and risks is likely to present a net benefit or cost to the sector.
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Table 2.2: Overview of opportunities and risks to economic sectors Opportunity/ Net loss/gain due to MSHP Net benefit Sectors Future trends with MSHP (narrative) Risk (cause) development or cost ‐700,000 to ‐1.4 million Risk tonnes Fish migration routes will be blocked, (capture USD 0.68/kg = USD 680/tonne flood pulses will be disrupted, and wet fisheries) land lost. A decline in fish populations
‐USD 476 million to ‐USD 956 likely to result. This is likely to be true million both for migratory species and species Fish 25,000 to 250,000 tonnes Net cost Opportunity which depend upon flood plains for (63,000 most likely)
Fisheries Some of this loss may be off‐set by the (reservoir USD 680/tonne introduction of reservoir aquaculture fisheries) but potential yields from this remain USD 17 million to USD 170 highly uncertain. million (USD 42.8 million most likely) ‐54% of river bank gardens Risk Loss of river bank gardens due to Net cost Riverbank garden loss in zones 2,3 and 4 inundation of long stretches of the production (riverbank USD 18 million ‐ USD 57 mainstream river in zones 2, 3 and 4. gardens) million/year Risk ‐ 7,962 ha of paddy Relatively small losses from inundation (inundated ‐ 22,475 tonnes of rice/year of paddy may be significant for at risk
forestry paddy and populations in zone 2 where little transmission ‐ USD 4.1 million/year alternative land is available. and
lines) Any reduction in sediment load and Paddy production flooding will lead to a decrease in Risk associated nutrient replenishment. It is not clear that the mainstream dams
Agriculture N/A will effect agricultural production (value of relative to the effects which are likely nutrients to to be felt due to mainstream Chinese agriculture) projects and tributary projects.
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Table 2.2: Overview of opportunities and risks to economic sectors Opportunity/ Irrigation projects associated with the Opportunity 17,866 ha of paddy hydropower developments are likely (increased 77,701 tonnes of rice/year to improve land productivity and rice irrigation) USD 15.54 million/year production in some areas. Some valuable environmental assets Risk upon which burgeoning ecotourism (degradation industry is based will be degraded or of natural N/A lost due to changes in the hydrology resource and ecology of the mainstream base) Tourism revenues resulting from these projects. Net cost Opportunity Tourism Large hydro‐electricity projects often (HP project attract (mainly domestic) tourism (for N/A viewing, example Hoa Binh dam in northern reservoir Vietnam) tourism) Mainstream hydropower is likely to Opportunity increase the navigability of the river as Freight transport N/A it will increase the depth of the river along significant stretches. However, (increased
this will be dependent upon designing navigability) dams such that they allow navigation. Which projects go ahead will affect the Opportunity Net benefit (increased N/A overall navigability of the river. navigability) Therefore, impacts on navigability and Navigation are dependent upon dam design Passenger transport Risk Even with navigation locks these (decreased N/A projects will increase the time taken longitudinal and probable costs of navigation connectivity)
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NATURAL SYSTEMS IMPACTS (ECONOMIC)
Loss of wetland and ecosystems that support economically valuable aquatic plants is also likely to represent a significant economic loss. The annual economic value of lost wetlands is estimated to be up to USD 7 million per year.
Changes in natural resource availability likely to impact the most vulnerable ‐ The impact of these changes in natural resource availability are likely to have the greatest impact on the poorest groups or Mekong riverine communities for a number of reasons, i) the poor generally have limited access to productive resources and therefore rely more heavily on environmental commons; ii) decline in food production in the basin is likely to affect price levels, the poor spend proportionately more of their income on food and this will have a significant effect on their food security; and, iii) There are likely knock on impacts as the increasingly attenuated livelihoods of the rural poor force increased rural‐urban migration, and lead to declining conditions in some urban areas. Conversely, the impacts of cheaper and more reliable power supplies are likely to accrue to a relatively wealthy section of the urban population.
Differential impacts will be experienced in different ecological zones ‐ Issues relating to land loss and resettlement are likely to be particularly acute in zones where replacement land is likely to be scarce, such as zone 2. Whereas the loss of fisheries will be particularly significant in zones 4 and 5, it is unlikely that the riparian zones will see any significant direct economic benefit from the development of MSHP. Benefits will depend upon expenditure decisions made by governments.
IMPACTS ON NATIONAL ECONOMIES
Economic opportunities and risks of LMB mainstream power vary from country to country. Importing countries will realize full benefits from the start. Exporting countries (the poorest) will take longer to realize the opportunities. Nationally, economic opportunities and risks are unlikely to be evenly shared. Economic benefits resulting from power production will be enjoyed in the power sector of importing countries and host countries alike. Though time it takes to translate the additional power made available from MSDP to economic benefit in the domestic electricity sectors in Lao PDR and Cambodia will depend on domestic load growth. With respect to revenue flow from export earnings for governments, until MDDP are transferred to the host governments at the end of what are likely to be 25 year concession periods, the economic benefits from export revenue be will be largely limited to net increases in government revenues – the size of which is contingent upon the particular financial structuring of the projects (e.g. loan and equity payments)6. The distribution of economic benefits realised as a result of increase government revenues will, in their turn, be contingent upon government fiscal management capacity and expenditure decisions.
Risk to fisheries in Cambodia of particular significance ‐ While fisheries loss is a risk borne by fisher folk throughout the basin, this is likely to impact Cambodia worst of all. Cambodia has a greater proportion of fisheries dependant population and upwards of 1 million people are likely to be affected by the loss of fisheries, which is currently and important component to GDP (account for between 8 and 16% of GDP).
The following table provides a summary of the sensitivity analysis for different dam groupings. This box focuses on sector and macroeconomic aspects. The comparative impacts on different dam groupings are
6 Debt will be paid off before the concession period ends.
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provided for each theme (e.g. power benefits, sediment, fisheries) in the discussion in each theme in the main text. Macro economic impacts depend upon the magnitude of the investments and the revenue flows that result. Moreover, by and large any effects will of greater significance in the smaller economies in Lao PDR. As all these effects are not localized they are not included in this analysis.
SENSITIVITY ANALYSIS OF DIFFERENT GROUPS OF LMB MAISTERAM DAM
(FOCUSING ON MACROECONOMIC FACTORS)
Cascade of projects in Lao – Net economic benefit to the power sector for this group of dams amounts to half (48.6 %) the estimated overall economic benefit in the power sector for all 12 MSDP. This cluster of dams offer the greatest possibility of for improving economic benefit for river navigation, provide river traffic growth that is projected materializes.
The significant adverse economic impacts of this cluster will relate to degree of loss of fisheries in the whole system7, as well as the more specific loss of riverbank gardens, loss of other agricultural land that is scarce in zone 2. 90% of riverbank gardens in zone 2, representing a production value of about USD 9 million per year would be lost due to this cascade. The agriculture losses are likely to be offset by the extension of irrigation in associated with Pak Chom project agriculture in this area, which would increase agricultural productivity in the area considerably. The potential for navigation benefits would be greatest in this reach of the river.
Around 80% of the aquatic habitats would be lost, representing a significant loss in terms of the value of ecosystem services, and the productivity of key aquatic resources. This cascade is expected to reduce the productivity of capture fisheries by 130,000 – 270,000 tonnes, an estimated value of USD 88.4 – 183.6 million per year, offset to the extent that reservoir fisheries production of 2,000 – 20,000 tonnes worth USD 1.4 – 13.6 million per year.
Middle Mekong projects ‐ – Net economic benefit to the power sector for this group of dams amounts to under one third (30.6% of the estimated overall economic benefit in the power sector for all 12 MSDP. While some agricultural land will be inundated, this loss is small compared to the large extension in irrigated land associated with the projects and consequent projected rises in productivity in the area. Around 22% of riverbank gardens in the zone could be lost implying an annual output loss of up to USD 9 million.
These projects are likely to affect a number of important ecotourism areas greatly reducing the economic potential for tourism in the area. Some ecosystem services and assets are likely to be lost although not to the extent of that experienced with the up‐stream cascade. Capture fisheries production is expected to decrease by 210,000 – 420,000 tonnes due to these dams, worth USD 142.8 – 285.6 million. Estimated reservoir fisheries production at 300‐3,000 tonnes worth an estimated USD 0.2 – 2 million is likely to do little to off‐set this loss.
Cambodia projects – Net economic benefit to the power sector for this group of dams amounts to about one fifth (20.5%) of the estimated overall economic benefit in the power sector for all 12 MSDP. Relatively small amounts of agricultural land will be lost, but plans for any compensatory extension of irrigation in the area are not known. Loss of river bank garden production due to inundation in the area is expected to amount of USD 2.7 million per year accounting for 45% of this kind of production in the area.
7 There continues to be a divergence of views within the MRC network of fisheries experts in the region on the relative affect of different groupings of mainstream project. MRC is addressing these divergences in scientific opinion to reduce under certainties.
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Large areas of important and productive ecosystems would be inundated meaning resulting in a loss of key environmental assets and services. These dams would inundate an area which is extremely important flora and fauna and would likely mean a loss of an important tourism asset and associated loss of economic potential.
Capture fisheries loss estimated for these dams is between 220,000 and 440,000 tonnes worth USD 149.6 – 299.2 million, beside the relatively small reservoir production of between 2,000 and 19,000 tonnes worth USD 1.4 ‐12.9 million.
2.3 HYDROLOGY AND SEDIMENT
The LMB mainstream projects are proposed at a time when the Mekong hydrological regime is undergoing a period of intensive change driven by rapid hydropower development on the LMB tributaries and on the UMB mainstream (in China). Nonetheless the projects will have wide implications to the future movement of water and sediment through the Mekong basin system. The key indicators of change are stream power, hourly, daily and seasonal fluctuations in the water levels along the Mekong River, and the fate and transport of coarse and fine sized sediment along the river.
STREAM POWER links key hydraulic features of the Mekong system, including: power production, energy dissipation, geomorphology, flow turbulence and sediment transport and is a measure of the energy available in the system to facilitate these processes.
Approximately 66% of the total length of mainstream in the LMB will be converted to reservoir transforming the river from a live river to a series of impoundments with slow water movement interspersed by downstream stretches with rapidly changing flow in response to dam operations. The effect of this on stream power is to concentrate the relatively uniform dissipation of energy along the entire length of the river (5‐20MW/km) to large expressions of energy in small reaches centred on the dam wall (up to 2,000 MW) and no dissipation along the hundreds of kilometers of reservoir.8 This concentration of energy presents significant benefit for electricity production, however it will also irreversibly alter other important natural processes, including: (i) major changes to sediment transport of all sizes, (ii) functioning of deep pools, (iii) major changes in transport of organic and woody debris, (iv) significant and irreversible changes in fisheries migration and passage, (v) additionally, stream power changes will have links with risk factors for anthropogenic uses of the river, such as detriments to navigation and detriments to fishing opportunities.
WATER SURFACE LEVEL CHANGES: The Mekong River has a strong flood pulse characterised by 4 distinct seasons and corresponding fluctuations in the water levels. LMB tributary and UMB Chinese hydropower will disturb the timing and duration of these seasons, but when combined with the LMB mainstream projects upper reaches of the LMB will no longer experience the ecologically important transition seasons.
8 Under a natural hydrological regime there are some sites where energy dissipation is concentrated, for example Khone Falls, however the process is overwhelmingly more uniform than with the LMB mainstream projects
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For 7 of the proposed projects, the dams will be sufficiently high that water levels in the reservoirs behind the dams will be above the highest ever recorded river elevations for significant distances upstream. This will have dramatic implications for riparian communities and riparian use of the river. Areas that were previously floodplains areas will be drowned by the proposed reservoirs. More than 5‐ 10% of the river valley, in the total distance of 1760 km will be affected by receiving inundation at levels never experienced in the history of data collection for the river. This will have significant impacts on:
• Irrigation infrastructure: almost half of all irrigation pump stations existing and planned for the Mekong mainstream will be affected by increased water levels. For some of these there is the possibility of reduced pumping heads from elevated water levels, however, the pump stations will need rebuilding, relocation and resizing to allow for operation at these new water levels and to turn the reduced pumping head into an economic advantage.
• River bank agriculture: The total loss of bank side growing areas from permanent inundation from the reservoirs in this distance will be a certain risk. Partial losses of bank side growing areas will apply to approximately an additional several hundred km of the mainstream river, associated with high water levels (see terrestrial paper).
• Floodplains: the majority of floodplains hydrologically connected to the mainstream in Zone 2 and 3 will be permanently lost as will seasonal in‐channel features (island, silt terraces, sand bars)
The changes in water levels could be greatly exacerbated by the operational strategy of projects. Peaking operation, which consists of maximising turbine discharge when the buying price for electricity peaks at a daily time‐step, could change greatly increase the rate of fluctuation of water levels from a historically seasonal phenomena to a daily or even hourly phenomena. There is the potential for hourly spikes in water level of up to 3‐5m at towns and villages located 40‐50 km downstream. Under unplanned and emergency releases these peaking events could be larger and could translate this distance downstream in 1‐2 hours giving very little time for notification.
COARSE SIZED SEDIMENT: there are currently no anthropogenic obstacles to bed load transport in the LMB mainstream, such that coarse sized sediment (coarse sand, gravel, cobbles) is conveyed downstream by saltation distance of a few tens of meters (through deep pools) to a few kilometers. The Yunnan cascade will reduce the bed load arriving in the LMB, this will result in a coarsening of the bed load as the river attempts to compensate by depleting storage of medium sized particles from the bed and banks. The addition of the LMB mainstream projects will:
• significantly reduce stream power and water velocity resulting in enhanced sedimentation and the formation of large deltaic‐type deposits at the head of each of the reservoirs. This will see sediment accumulate in sections of the river where it has never accumulated in the past;
• increase the rate of sedimentation in areas of the reservoir not influenced by scour flow from the spillway and sediment gates – dependent on the sequencing of construction;9
9 Upstream scour/sediment removal associated with opening gates can only induce localised scour affects and will likely affect sedimentation near the dam wall not along the 100km of reservoir.
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• change the mechanics of sediment transport, by reducing the velocity of mean annual flood flow through the reservoir so that medium sized particles which moved in suspension will now move only partially in suspension and coarse sized particles which had moved partially in suspension and partially as bed load will now move as bed load causing greater retention rates in the impoundment of both medium and coarse sediment;
• increase down‐cutting and channel bed and bank erosion in alluvial reaches of the Mekong (Zone 3);
Further, by 2030 in the scenario without LMB mainstream hydropower, the reduced sediment load is expected to be partially offset by increased uptake of medium sized sediment from the alluvial reach between Vientiane and Pakse. This could delay instability of the channel banks of the Cambodian floodplain by the order of decades. The Cambodian projects (Stung Treng and Sambor) will reduce stream power and increase retention of this compensated load in the reservoir eroding the potential buffer period before downstream reaches (e.g. Phnom Penh) experience erosion and bank instability.
FINE SIZED SEDIMENT: the load of suspended sediment is estimated at 160‐165million tonnes/yr, up to 80% of this will be removed by predominantly by storage projects in China and the 3S region. In the Cambodian floodplain and the Mekong Delta, the gradient becomes small and the load is primarily clay silt and fine sand, with maximum transport of suspended load from Stung Treng to Kampong Cham. The addition of the LMB mainstream projects will:
• reduce velocities in the reservoir and induce some deposition of fines in backwater areas of the reservoirs;
• decrease the concentration of suspended sediments in the channel downstream of reservoirs;10
This reduced suspended load will have vital implications for the transport of nutrients and stability of the Mekong Delta:
NUTRIENTS: ~18,000km2 of the Cambodian Floodplain is naturally fertilised by nutrients attached to suspended sediments. The reduced sediment load will have critical impacts on the natural and human systems which rely on these nutrients, including primary production, flooded forests, floodplain fisheries and agriculture.
DELTA STABILITY: the reduced suspended load will reduce the Mekong marine sediment plume affecting:
o Coastal fisheries which rely on primary production associated with the nutrient rich sediment plume
o Greater instability and erosion of channels in the delta with knock‐on effects for irrigation works and inland water‐way transport
o Increased coastal erosion and reduced delta‐building along the eastern shoreline of the delta.
10 Particularly an issue in the first two decades following dam construction
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2.4 TERRESTRIAL SYSTEMS
The Mekong mainstream dams in Laos will have a significant local impact upon the terrestrial ecosystems and agriculture in the areas of inundation.
There will be little direct impact outside the areas of inundation and land take for transmission lines and access roads. The reservoirs inundate the river channel, with some smaller areas of forest and cultivated land inundated along the river banks for most of the dams.
The two Cambodian dams differ in that they will flood larger areas, including forest and cultivated land.
The reservoirs will change the landscape of the Mekong river valley, maintaining the water levels slightly above the current high flow levels, with little seasonal changes. The projects will have an impact on terrestrial biodiversity which is of international significance – about half the length of the Lower Mekong has been recognized as Key Biodiversity Areas (even though only a small length in Zone 3 is under formal management as part of a National Protected Area), and the river above Stung Treng is a designated Ramsar Site. Significant parts of the Key Biodiversity Areas will be affected by the dams.
Small areas of cultivated land will be lost, but the total loss in production will be more than recovered by irrigation schemes in three of the dams. River bank gardens in the reservoir areas will be lost, with some significant impacts on livelihoods of riparian communities.
2.5 AQUATIC SYSTEMS
Cascade of 6 dams upstream above Vientiane would cause very significant changes to aquatic ecosystems. Over 80% of zone 2 would be changed from a free flowing river to a regulated set of reservoirs that run into each other. Similar proportions of all the aquatic habitats (rocks and rapids, riffles, sand bars and deep pools) would be changed, with a consequent loss of breeding and spawning areas.
The aquatic biodiversity of zone 2 would become seriously impoverished, the more so because there are few major tributaries entering the zone, which can provide alternative spawning areas. Productivity of this zone would also decrease, especially for Mekong river weed. The loss of critical diverse aquatic habitats above Vientiane, e.g. Pak Chom, which probably mark a transition point between the upper river and the middle reaches, represents a loss of a unique area in the Mekong, possibly comparable in importance, though not in scale, to aquatic ecology as some of the other areas of aquatic habitat diversity lower down the system, e.g. in Siphandone.
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The cascade of project would have an immediate downstream impact extending at least down to Vientiane as a result of daily variations in flow, and sediment trapping and flushing discharges. However, these will certainly have been balanced out by the time the river has passed through the rest of Zone 3. The biggest impact from an aquatic ecology point of view will be as a barrier to migration of fish. The lower part of Zone 2 acts as a transition between the upper reaches and middle reaches of the Lower Mekong and hence indirectly with the lower reaches, the delta and the sea.
The biggest loss would therefore be upon connectivity between the sea and the Upper Mekong. Even if all the dams in the cascade are fitted with efficient and effective fish passages, the stretch of six dams in cascade over a distance of nearly 800 km represents an impossible barrier for the long distance migratory species.
Middle Mekong dams: The two dams in the middle reaches of the Mekong, Ban Koum, shared between Thailand and Laos, and Latsua which lies completely in Laos, will have less an effect upon Zone 3 itself than the cascade above Vientiane has upon Zone 2.
However, Ban Koum occupies a stretch of the river, which is distinct and ecologically significant in the context of Zone 3, with almost all the deep pools and rocky/rapid areas in the Zone. These two dams are intended to operate as near to run‐of river as possible with minimum daily draw down, and so should have little impact downstream in terms of daily flow variation. However the influence of Ban Koum will be felt in the aquatic ecology as far downstream as Pakse, and the influence of Latsua will be felt well down into Siphandone, but probably not beyond Khone Falls.
These two dams will act as a significant break in the connectivity of the mainstream between the lower parts of the Mekong and the middle and upper reaches. If these two dams were constructed with effective fish passage for both upstream and downstream migrations, this might be less important, but current designs of fish passage are unlikely to be effective for more than a few species. The relevance of fish passage in this section is not just relevant for the fishery in the mainstream, but also for the tributaries in southern and central Laos. It is likely that the fish productivity and biodiversity would be lost from these tributaries as a result of these two middle reach dams.
The lower Mekong dams in Cambodia would inundate one of the richest and most biodiverse areas of the entire Mekong system, an area of global importance to aquatic biodiversity. This is a unique area with immense diversity of river morphology, aquatic habitats and landscape value, both in the Mekong system, but also in other major river systems. Because of the topography and nature of the river channel, the area of inundation would be much larger than the dams upstream, and cover many of the islands, deep pools, rocks and rapids and sandbars.
They would involve the loss of rare and endangered fish species, and most probably be the final threat for the Irrawaddy Dolphin. The area is an important spawning and breeding ground for many species, and it is not clear if alternative breeding grounds would still be available.
If these lower Mekong dams were to be constructed, the biggest impact to the system would be in terms of the connectivity of the system, especially for fish migration. The Mekong above Kratie to the Laos border and up the Khone Falls is an important destination for fish migrating out of the Tonle Sap. The combination of Sambor and Stung Treng dams would effectively stop this. Sambor dam would also stop the important fish migration route up the 3S rivers, especially the Sekong. The downstream flows from Stung Treng dam might also alter the fishes ability to navigate up the 3S rivers.
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The smaller hydropower schemes at Khone Falls – Don Sahong and Thakho – are of significance here for different reasons. Thakho HPP is true run‐of‐river involving a diversion or a proportion of water around the Khone Falls. It will have no effect upon fish migration. Don Sahong would effectively block the only channel that is known to provide a year‐round route for migrating fish. Unless alternative and effective routes for fish passage are provided, this would be a barrier for some of the important small commercial species that use it during the dry season. Yet, the barrier effect of Don Sahong would probably become almost irrelevant if Sambor and Stung Treng dams are built.
Downstream of Sambor, the aquatic ecology of the river below Kratie would be affected by changing daily flow patterns and sediment trapping and flushing. It is probable that the reservoirs in Sambor and Stung Treng would allow more sediment to drop out than the narrow in‐channel upstream dams, so there are likely to be losses of sediment to the river downstream, that will not be rectified by sediment flushing.
Possible indirect links with other future trends: The change in the primary productivity of the aquatic ecosystems of the river will have implications for the overall productivity of the river in general and in the reservoirs themselves. It is unlikely that they will be as productive in terms of the fishery as Nam Ngum, which depends largely upon the nutrient inputs from a number of different tributary rivers. The cascade dams above Vientiane in particular have very few tributaries and are a very different type of reservoir. This has implications for fish catches and the livelihoods of the riparian communities. The decline in Mekong River weed in the mainstream of zone 2 will also have serious implications for the supply of this product and another source of riparian livelihood.
During construction, water quality issues and risks have implications for river users and sources of drinking water, i.e. affecting public health of riparian communities. During operation, these risks should be less, except during periods of sediment flushing, when drinking water sources will be put at risk by the high sediment concentrations.
The changes to cultural ecosystem values of the river will affect the social, cultural and religious structure of communities along the river, especially those adjacent to the reservoirs or immediately downstream of the dams. The perception and willingness to pay for river based activities of visitors and tourists to the Mekong region will be affected, especially during the construction period, and tourism products and marketing will have to be changed once the dams and reservoirs have been created to re‐develop river based tourism. This has both important livelihood and economic implications.
2.6 FISHERIES
Total fish production at risk of mainstream dam development ranges between 700,000 tonnes and 1.4 million tonnes (170,000 – 340,000 tonnes for Cambodia, 60,000 – 120,000 tonnes for Laos, 250,000 – 500,000 tonnes for Thailand and 240,000 – 480,000 tonnes for Vietnam).
These losses could be partly compensated by the production of reservoir fish. The total amount of reservoir fish produce would range between 25,000 and 250,000 tonnes, the most likely scenario being 63,000 tonnes.
Options to mitigate these effects (mainly fish passes and use of reservoir fisheries, respectively) are not capable of compensating for the losses. Due to the diversity and magnitude of Mekong fisheries and migrations, no mitigation measure will prove effective if all 11 mainstream dams are constructed.
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SENSITIVTY ANALYSIS
Table 2.3: Fisheries opportunities and risks for 3 key clusters of LMB mainstream projects
Components of Likely expected opportunities or risks caused by this component the HP plan • 262 species (22% of endemics) (1) Upstream • The migration barrier effect will apply to 40 sub‐basins cluster of dams • Hydrologically, the area is dominated by effects of Chinese dams • a drop in the recruitment of local species is expected even in absence of mainstream dams. The contribution of these upstream species to the fish biodiversity of the basin is very important (in particular Balitoridae) • 90% of river will be converted to reservoirs if 6 mainstream dams completed • 41 species at specifically at risk, including the Giant Mekong catfish (at risk for extinction if dams completed) • the risk of fish production losses in case the 6 upstream mainstream dams are built amounts to 130,000 – 270,000 tonnes.
Reservoir fish production would range between 2,000 and 20,000 tonnes of fish, the most likely estimate being around 7,000 tonnes of reservoir fish per year in this zone. • 386 species (29% of endemics) (2) Middle cluster • Composed of 40 sub‐basins of dams • The Latsua dam would have much more negative impact on fish migrations than the Ban Koum dam because it would block access to the Mun/Chi system (70,000 km2). The Latsua dam would have the same impact than the Pak Mun dam on Mun‐dependent fish species, plus additional impact on species migrating up the mainstream. • The Ban Koum and Latsua mainstream dams would create 147 km2 of reservoir, i.e. 23% of the mainstream between Pakse and Vientiane would be turned into a reservoir. This area can be expected to produce between 300 and 3,000 tonnes of reservoir fish, the most likely estimate being 330 tonnes • The risk of capture fish production losses in case the 2 mainstream dams of the middle cluster are built amounts to 210,000 – 420,000 tonnes
• 669 species (14% of endemics) (3) Downstream • Composed of 24 sub‐basins cluster of dams • Migration barrier: six sub‐basins affected, including the Sekong‐Sesan‐Srepok system (second largest in Mekong, area 78,648 km2) • If 11 reservoirs are built, 55% of the mainstream will be turned into a dam reservoir. If Cambodian dams are not built, “only” 48% of the mainstream would be turned into a lake • The risk of fish production losses in case the 2 mainstream dams of the downstream cluster are built amounts to 220,000 – 440,000 tonnes • The loss of floodplains inherent to these 2 dams corresponds to 3,000 to 12,000 tonnes of fish only • The Stung Treng and Sambor mainstream dams would create 950 km2 of reservoir. This area can be expected to produce between 2000 and 19,000 tonnes of reservoir fish, the most likely estimate being 47,000 tonnes
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The MRC BDP2 has released a draft report on impacts of mainstream dams on fisheries resources (May 2010). The findings of this report are in line with the findings of the SEA team. Assessments of impacts of dams on biodiversity are more detailed in the SEA report, whereas impacts of dams on capture fisheries and aquaculture production are more detailed in the BDP2 report.
The assessment of possible losses, detailed in the SEA fisheries report, ranges between 700,000 and 1,400,000 tonnes. The possible losses quantified in the BDP2 report amount to 600,000 tonnes. The 2008 MRC panel of experts also estimated the possible losses at 700,000 – 1,600,000 million tonnes (Barlow et al. 2008). Whatever the discussion about the range of possible losses, the most conservative figure agreed by all studies and experts, i.e. 600,000 tonnes of fish possibly lost, representing the annual inland fish production of the whole West Africa. All experts and studies agree that building 11 mainstream hydropower dams implies an ecological and food security risk equivalent to depriving 15 West‐African countries of all their freshwater fish.
The SEA and BDP2 fisheries studies are also in agreement about the low fish production to be expected from reservoirs. The SEA study estimates this production to be 25,000 ‐ 250,000 tonnes, the most likely scenario being 63,000 tonnes, whereas the BDP2 study estimates this production to be 16,000 – 64,000 tonnes.
Several important aspects in fisheries have not been covered by the SEA or by BDP2 study. These are:
the impact of sediment retention on water productivity and fish production;
the changes in quality of fisheries products in case of change in species composition, in particular the nutritional value of the newly dominant species and the possible impact of human diseases such as liver fluke present in multiple small cyprinids;
the changing value of fisheries products, depending on changes in catch composition and on market demand for a scarcer product;
the socio‐economic issues and shifts of benefits between social groups following losses and changes in species composition.
Ultimately, both SEA and BDP2 studies are initial attempts to assess the impact of investments worth USD 18,847 million on a resource worth USD 2,100 – 3,800 million. The magnitude of possible impacts calls for major additional investment in in‐depth assessments of impacts of hydropower development on food security in the Mekong Basin.
2.7 SOCIAL SYSTEMS
Overall advantages and risks associated with mainstream hydropower development and identified by different stakeholders during the course of the SEA, are outlined in Table 1. Almost all direct impacts listed are permanent and irreversible.
The MRC classifies a 15‐km wide corridor on either side of the Mekong River as the highest impact area for hydropower on the mainstream. Corridor populations totaling approximately 23,500,000 persons could be affected by mainstream dams (Table 2). While the total corridor population amounts to more
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than 23 million people, 78% of these (18,382,086) live within 5‐kms of the Mekong mainstream11. At more than half the corridor population (51.2%), Vietnam has both the highest population numbers and greatest population percentage, and Cambodia the highest national percentage (57.2%), living in the 15‐ km Mekong corridor.
Table 2.4: Populations in a 15km corridor adjacent to the Mekong River
% of national % of corridor Corridor population living population per Country Population in the corridor country Cambodia 7,601,352 57.20% 32.50% Laos 2,004,515 35.30% 8.60% Thailand 1,901,171 2.80% 7.60% Vietnam 11,974,813 14.80% 51.20% All countries 23,481,851
Indirect impacts may affect a larger number of people, but less drastically and immediately than direct impacts. Adverse indirect impacts are most likely to be experienced in the Mekong corridor, and mainly by those living within good proximity of the Mekong River (i.e. within 5‐kms.). Of the 4 LMB countries, Vietnam has the highest dependent proportion of its corridor population living in closest proximity to the Mekong (89%), followed by Cambodia (78%), Laos (50%) and Thailand (38%).
The proportion of dependency reflects both the very high rate of dependency in different countries on Mekong river irrigated agriculture (Vietnam) and fisheries (Cambodia). Laos has a substantial percentage of its riparian population (50%) within 5kms proximity, while Thailand has the least (38%).
Apart from immediate proximity to the Mekong River, local administration is also affected by hydropower projects. Relative capability and transparency of local administration has a direct bearing as to the severity or otherwise of the extent of social and livelihood impacts. Pak Chom and Ban Koum will affect the largest number of districts, and the highest district populations will fall in their ambits of activity. These are the districts where indirect impacts will be most experienced. The Table shows the total population of all districts in the 3 immediate impact zones of head pond, construction site and immediate downstream areas (20kms). Several districts are affected by more than one dam but the overall total counts each district once only.
Additional people may be indirectly affected, particularly in hinterland districts dependent on connected river systems which may experience water flow changes, increased sedimentation, or fish reduction. This would include substantial numbers of people in the Tonle Sap who are annually or seasonally dependent on fisheries for their livelihoods. Cambodia will be most indirectly affected, with an estimated 43% loss in its fisheries, followed by Vietnam with an estimated 23% loss12. In Cambodia, this works out at some 1 million fisheries‐dependent livelihoods at risk.
11 Mekong River Commission, "Integrated Basin Flow Management Progress Report (IBFM)", 2007. 12 Ton Lennaerts, "Economic, Environmental and Social Impact Assessment of Basin‐wide development scenarios", Initial Findings from Assessments, Mekong River Commission, RTWG presentation, February 2010
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Table 2.4: Social Theme: Advantages and Risks of Hydropower Development
No. ADVANTAGES RISKS Poverty Reduction Revenue benefits not equably shared, leading to higher costs for agencies dealing with associated impacts (e.g. health agencies having to pay for public health consequences, forestry 1 National revenue generation which can be used to develop other sectors agencies dealing with increase in logging & poaching activities) Those directly affected may not include those benefiting from national poverty alleviation strategies ‐ assumption that the developer will address poverty alleviation of affected people is 2 Transport infrastructure improved, augmenting regional road communications networks not always reliable
Public infrastructure improved and associated training provided (e.g. health stations and 3 health personnel) Developer refusing to pay high costs of impact alleviation Projects approved without proper SIAs conducted, under‐estimate of affected people, and 4 Market access improved with trans‐river bridges failure to allocate sufficient finances to address impacts
Electricity generation supporting long‐term local and national social and economic Loss of established land‐ and river‐based natural resources, including common property 5 development (schools, hospitals, mining, local value‐adding industries) resources
Decreased national energy vulnerability, particularly in the face of rising demand which 6 renewable sources cannot meet Replacement land of equal size and productivity unavailable
Alternative work and service provision opportunities for local people during construction Loss of livelihoods, leading to increased food insecurity and landlessness, poorer living 7 period conditions and homelessness Loss of homes, property, community infrastructure, or buildings/locations of cultural, historical 8 Cheaper national price of electricity or spiritual significance Project‐related work opportunities temporary. Little opportunity for skills development, as 9 Higher groundwater levels could facilitate pumped irrigation skilled work reserved for outside labour
10 Facilitates inland transport Electricity supply may not be available to affected people
11 Lower operational costs and maintenance than other energy sources Private river‐based irrigation pumps damaged by rapidly fluctuating water levels Loss of transport‐related livelihoods for those with small boats unable to cope with changed 12 Flood mitigation and control water levels and water flows
Pace and intensity of economic investment and provincial development increasing faster than 13 Ensuring greater voltage stability government capacities to deal with it on a number of fronts
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g g g y g p
Health & Nutrition
Impact mitigation measures properly implemented can lead to improved living standards, Increased morbidity & mortality through increased vector‐borne disease, transmission of STDs & 1 improved sanitation, reduction of chronic health problems HIV/AIDS via construction workers and increased number of sex workers Loss of fisheries with associated impacts on livelihoods and protein intake, leading to higher 2 Upstream dams affecting fisheries less than downstream dams incidence of stunting and wasting Higher groundwater levels and/or changes in groundwater flows, leading to waterlogging with potential impacts on sanitation‐related health, increased risk of vector diseases, property 3 damage and effects on crops
4 Poorer water quality, with consequences on fish loss, livelihood and healthimpacts Changes in water flows leading to unexpected flooding and consequent risk of loss of life, 5 property and land Resettlement Benefits‐grabbing by stronger groups, leading to marginalisation of weaker groups ‐ high risks of 1 Infrastructure improvements in resettlement areas "boom and bust"
2 Improved access to infrastructure, including health facilities, markets, etc. Restricts traditional access to land‐based resources with no viable alternatives offered Poor resettlement process leading to break‐up of social and family networks, with added loss of 3 social and cultural capital Associated infrastructure improvement (e.g. roads) can result in opening up previously isolated areas, leading to land‐grabbing, increase in illegal logging, mining, wildlife poaching, and people‐ 4 trafficking from remote villages Operational impacts of dams often difficult to fully anticipate, identify, quantify or mitigate, 5 particularly downstream Time needed for planning, constructing and filling reservoirs can discourage investment in the 6 area and cause losses to area residents
Upstream erosion from inadequate watershed protection leading to landslips, causing post‐ 7 resettlement loss of property and requiring additional community relocation and livelihood loss 8 Transboundary costs of watershed protection ‐ rights and responsibilities unclear Difficulty of identifying what is a national and what is a transboundary issue, and related 9 financial consequences 10 Loss of cultural and spiritual assets and location‐specific associations Scarcity of paddy land making land‐for‐land options unlikely to find replacement land of 11 comparable productive and economic value
12 Downstream erosion causing loss of riverbank gardens Lega l and institutional frameworks for social safeguards, and monitoring capacity, poorly 13 understood (particularly at provincial and district levels) and legislation inadequately linked to Governments unclear how to support prior notification process of MRC to facilitate different 14 national decision‐making
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Table 2.6: Number of affected provinces, districts and district populations for mainstream dams
Total Affected No. Affected No. Affected District No. Dam Name Provinces Districts Population
1 Pakbeng 4 8 223,659
2Louang Prabang 2 4 159,204
3 Xayaboury 2 4 202,198
4Pak Lay 3 7 282,544
5 Sanakham 2 4 160,974
6Pak Chom 4 13 588,189
7Ban Koum 3 8 413,140
8Lat Sua 2 4 255,160
9Don Sahong 2 5 250,217
20 Thakho NA NA NA
11 Stung Treng 1 2 52,326
12 Sambor 1 2 145,610 Totals 13 47 2,094,749
2.8 CLIMATE CHANGE
The relationships between the proposed mainstream projects and climate change is likely to be significant. There would be direct and indirect effects. The direct effects are in two ways: (i) the contribution of the projects to climate change through green house gas emissions, and (ii) the direct effects of climate change on the projects through increased runoff and flow and in extreme flood events.
On the first point, an overall question is ‐ what is the net impact of LMB hydropower on GHG emissions in the power sector in the Mekong, nationally and regionally. This requires subtracting the total reservoir emissions from the total thermal avoided emissions (where hydropower displaces natural gas, coal or oil‐ based generation that currently dominates the LMB power sector) to arrive an assessment of whether hydropower provides a net opportunity or risk as regards to climate change mitigation (GHG emission reduction). The methodologies for estimation of reservoir emissions in particular are contested because of the complexities of the science. Preliminary assessment indicate there is a net reduction in the region of about 80 million tones CO2 /yr GHG emission in the regional power sector overall. The amount attributed to mainstream dams would be in the order of 50 million tones CO2 per year.
The mainstream projects in Cambodia have high total GHG emissions relative to other hydropower projects in the basin because of their large capacity, location and reservoir size. Yet, overall, the mainstream dams are more attractive than most alternative power sources, other than wind and nuclear, for their relatively small impact on climate change.
The most important direct climate change effect on the mainstream projects would be (i) the increase in runoff during the wet season bringing with it increases in sediment load, (ii) an increase in flow in the
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range of 9% to 22% taking into account UMB and LMB mainstream and tributary dams, and (iii) an increase in the incidence, depth and duration of extreme flood waters. LMB mainstream dams could be subject to seasonal and extreme event peaks in flow well beyond their normal operating design standards.
Assuming a mainstream project design life of 100 years:
• Project structures designed for a 1 in 100 year event will see the probability of this event occurring over the design life increase from 63% to ~100%.
• Projects structures designed for a 1 in 1,000 year event will see the probability of this event occurring over the design life increase from 10% to 63%.
• Project structures designed for a 1 in 10,000yr event will see the probability of this event occurring over the design life increase from 1% to 10%.
This places emphasis on the MRC Preliminary Design Guidance (PDG) for lower Mekong Mainstream dams (MRC, 2009) and in particular the provisions in the PDG for a consistent approach to the safety of dams. The complex inter‐linkages between climate changes, the mainstream dams and other trends in the Basin would results in some of the most significant synergistic effects.
Reduced food security due to climate change would be aggravated by the mainstream dams, as would water quality. The contribution of the projects to hardening of natural systems would increase biodiversity losses and natural system instability. Those factors would affect poor communities most.
Increased annual runoff and flow throughout all catchments of the basin would increase its potential hydropower capacity along tributaries and the mainstream. That additional capacity and its technical and economic feasibility requires further assessment as a potential factor influencing the need for or phasing of mainstream projects in meeting power demand.
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3 PROPOSED LMB MAINSTREAM HYDROPOWER
3.1 DESCRIPTION OF THE PROPOSED MAINSTREAM PROJECTS
3.1.1 PROJECT TYPE
Hydropower projects generate electricity by utilising the stream power available within a river system and converting the kinetic energy of flow into electrical energy. For rivers with large flows, energy can be extracted from the flow itself, or an impoundment can be built to store potential energy and control generation through dam release leading to two distinct types of hydropower: storage and run‐of‐river projects.
The proposed LMB mainstream dams are characterized as low head dams that span part of, or the entire mainstream channel in the Lower Mekong Basin. These projects would employ Kaplan or ship propeller‐type turbines, which function effectively with low heads and high volumes of water to generate power and have efficiencies typically in the order of 85%. The gross heads of these projects would vary between 6.5 m to about 35 m, though this vertical head (the distance between the normal water level in the reservoir behind the dam and the tail water level below the dam) would vary significantly between monsoon periods (when the head is small but the flow is large) and low‐flow seasons (when the head would be the greatest due to the much lower river flows and consequent lower tail water levels).
The actual dam height as measured from the bottom of the foundations in the river bed to the top of the dam structures can be as high as 80 m. As a reference, the eight dams on the mainstream in China that are completed, under construction or planned vary from 67 m to 248 m head (for Jinghong and Xiaowan respectively).
The 12 proposed mainstream developments are of three of three general types:
1. Dams that span the mainstream Mekong that involve limited inundation outside the mainstream channel: The 6 proposed dams from Pak Beng (the upper most dam in Lao PDR) to Pak Chom share similar broad characteristics. They typically span the Mekong river where it is 800‐1,200m wide and has steeper valleys. The reservoirs forming behind these dams, typically 100 to 120 or more km would generally be confined to the river channel, except at confluences with major tributaries and other natural floodplain where the reservoir will flood land areas. The dams further downstream at Ban Koum and Lat Sua have wider channels and some floodplain areas that would be inundated.
2. Dams that span parts of the braided Mekong mainstream or diversion schemes: This includes the proposed Don Sahong project (240 MW) which is the only dam project which does not span the entire width of the Mekong mainstream, consequently the project is smaller than the others. It also includes the Thakho (60 MW) run‐of‐river diversion project that will divert a portion of one of the main braided channels around Khone Falls, which does not involve a dam. It is in the same area as the proposed Don Sahong.
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3. Dams that span the mainstream Mekong or several branches that involve significant inundation outside the mainstream channel: For the two proposed floodplain projects in Cambodia (Stung Treng and Sambor) the approach is to have concrete dams span the main river channels flanked by earth embankment dams totaling between 10 km and 18km respectively in length. The reservoirs forming behind these structures would inundate larger areas of floodplain with total areas ranging from 200 to 620 km2. Installed capacity range from 980 MW (Stung Trek) to 2,600MW (Sambor) with a maximum discharge through the turbines of 18,000 m3/s at Sambor (though Cambodia notes that a scaled‐down version of Sambor is also feasible). Like the other projects, the storage capacity of these projects is limited to a few days or less and they would propose to use low‐head Kaplan generation units.
Project profiles: Profiles for the 12 mainstream projects were prepared during the SEA Inception phase (Volume 2); a summary of the salient features of the projects is presented in Table 1 below. A more general picture is run‐of‐river projects do not have the capacity to regulate flow and rely on the daily flow rate to generate power; this makes output subject to weather‐dependent flow conditions. Storage projects involve large impoundments and allow the operators greater control, however, also with greater disruption to the natural hydrological regime and other knock‐ on environmental and social consequences. Typically hydropower projects are not purely storage or run‐of‐river but are found on the spectrum that ranges between these two modes (see figure 3.1). For the LMB mainstream projects some, like Thakho are purely run‐of‐river, while others like Xanakham and Sambor have some potential for short‐ term storage.
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Figure 3.1: Types of hydropower projects in the Mekong Basin – the spectrum from storage type to run‐of‐river
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Table 3.1: Salient features of the LMB mainstream projects
MANAGEMENT STATUS DESIGN SPECIFICATIONS DIMENSIONS
)
DAM
DATE
(m)
Energy (mcm STATUS
Level
Energy Level
(m)
AREA
(m3/s)
POTENTIAL dam
Capacity
Capability
STATUS )
of
(m)
Head Annual ) ) )
LOCATION
Design
Supply DEVELOPER
Annual Storage Supply
COMMISSION EARLIEST (MW) (MW MAINSTREAM Length Height DESIGN ENVIRONMENTAL ASSESSMENT Rated Plant Discharge Installed Peaking Mean (GWh Firm (GWh Full (mamsl Low (Mamsl) Live RESERVOIR (km2)
Pak Beng Lao PDR Datang International 2016 MoU, IEE submitted 943 76 Power Generation feasibility 31 7,250 1,230 1,230 5,517 4,073 340 334 442 146
Louang Lao PDR PetroVietnam 2016 MoU, Feasibility 1,106 68 Prabang Power Corporation feasibility study, 40 3,812 1,410 1,412 5,437 4,205 310 308 734 89 Xayaburi Lao PDR SEAN & Ch. MoU, Feasibility 810 32 Karnchang Public Co 2016 feasibility and full ESIA Ltd submitted 24 6,018 1,260 1,260 6,035 5,139 275 270 225 61
Pak Lay Lao PDR CEIEC and Sino‐ 2016 MoU, IEE submitted 630 35 Hydro feasibility 26 4,500 1,320 1,320 6,460 4,252 240 237 384 67
Sanakha Lao PDR Datang International 2016 MoU, Not yet 1,144 38 m Power Generation feasibility 25 5,918 700 1,200 5,015 3,978 220 215 106 70
Pakchom Lao PDR N/a 2017 MasterPla Not yet 1,200 55 n 22 5,720 1,079 1,079 5,318 5,052 192 190 12 108
Ban Koum Lao PDR Italian Thai Asia 2017 MoU, Not yet 780 53 Corp. Holdings feasibility 19 11,700 1,872 1,872 8,434 8,012 115 115 0 234 Latsua Lao PDR Charoen Energy and MoU, pre‐ Pre‐feasibility 1,300 27 Water Asia Co Ltd 2018 feasibility study submitted 10.6 10,000 686 686 2,668 1,524 97.5 95.5 0 10 Don Lao PDR Mega First PDA, Full EIA 1820‐ 10.6‐ Sahong 2016 detailed submitted, 720‐ 8.2‐ planning Additional 2730 8.3 studies 17 2,400 240 240 2,375 1,989 75 72 115 3 Thakho Lao PDR CNR & EDL MoU, pre‐ IEE submitted Channe n/a diversion 2016 feasibility l ‐ 16 380 50 50 360 71.7 68.7 n/a n/a 1,800m Stung Cambodia Vietnam Urban and MoU, pre‐ Not yet 10,884 22 Treng Industrial Zone N/a feasibility Development Inv. Corp 15 18,493 980 591 4,870 2,937 55 50 70 234
Sambor Cambodia China Southern 2020 MoU, pre‐ Pre‐feasibility 18,002 56 Power Grid feasibility submitted 33 17,668 2,600 2,030 11,740 9,150 40 39 465 716
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3.1.2 LMB MAINSTREAM PROJECT OPERATIONS DURING WET AND DRY SEASON
Typically these dams will hold the water above what is normally the high flood level all year round and thus eliminate annual cycles of raising and lowering water levels. Typically these reservoirs have a storage capacity in the order of a few days (less than 70mcm) and can operate continuously or under peaking. Supply levels in the reservoirs can be greater such as for a 5 m draw down from normal water levels in advance of major storm events. Figure 3.2 presents the reservoir inundation areas for the Xayaburi and Stung Treng projects as an example of the range of reservoir type in the group of proposals, all reservoir maps are located in the Annex. These projects each have an installed capacity of about 700 MW – 1,400 MW, and a design discharge through all turbines of 3,000‐12,000 m3/s. The capacity of the turbines is loosely comparable to the average annual flow expected in the river at the given reach. In the wet season the majority of the flow would be over the spillways.
An example is shown for the Luang Prabang project below (figure 3.3), which is indicative for the other LMB mainstream projects except for Thakho. During the calendar year the low storage capacity means that the water levels in the reservoirs and downstream reaches will vary with season:
• January – May/June: water levels in the reservoir will be kept close to full supply level and above the maximum observed water level with the dam passing the dry season flow through the turbines. Downstream water levels will be comparable to dry season water levels in the channel providing close to maximum available hydraulic head but minimum flow rates. During this period projects will be generating below rated capacity.
• June – August: As the discharge in the river crosses the annual average the turbines will be generating at peak capacity. During this time there is the potential for peaking generation at a daily time step. Water levels in the reservoir would remain close to the full supply level with continuous operation and under peaking operations could fluctuate by 10m during the day. Downstream water levels with continuous operation would approximate the expected seasonal water levels without mainstream projects. Under peaking operations downstream water levels could vary by 4‐8m between peak and off‐peak periods.
• August – October: As the river approaches peak flood, the turbines will not be capable of passing the increasing flows such that all the spill way and other gates would be opened. This would result in flood levels up and downstream of the dam with minor head difference and a reduction in the power generation potential of the project during this season.
• October – November: As the flow drops towards the annual average there will be a period of optimal power generation with the potential for peaking operations. During this time water levels will be similar to the July‐August block
• November – December: then as the flow continues to drop to the dry season low, water levels up and downstream of the reservoir will experience fluctuations comparable to January to May above.
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Figure 3.2: Reservoir inundation areas: (left) Stung Treng – the flat topography results in a significant area of reservoir outside the mainstream channel. The reservoir has a length of 40.4km, surface area of 234km2 and volume of 1,550mcm directly affecting some 20 villages and towns; (right) Xayaburi – the steep incised valleys of Zone 2 result in greater confinement of reservoirs to the river channel. The reservoir has a length of 96.8km, surface area of 61km2 and volume of 150mcm directly affecting some 35 villages and towns
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Figure 3: Cross‐section of a typical run‐of‐river power house: illustration of the Luang Prabang project
3.1.3 TYPICAL LIFE‐CYCLE FOR THE PROPOSED LMB MAINSTREAM PROJECTS
At the soonest LMB mainstream projects could enter the Mekong system in 2015, with construction taking between 7 and 15 years. If multiple projects are approved and construction is staggered then there could be construction along the Mekong River for the next two decades. All projects are likely to be BOT (Built Operate Transfer) projects, which would allow the developer to operate the project for 25 years as a private venture before transferring ownership over to the national government. During this period the government would receive royalties on revenues generated by the project. After hand over, the project reverts to full ownership of the government and the management arrangements state that time would be decided which may include retaining the current operator under a management contract. .
During the concession period operation and maintenance would be provide the private developer following terms of the concession agreement and regulations established by the national regulatory body. In general, certain increased expenditure at the outset can increase the design life of project components and help minimize future maintenance requirements and prolong component end‐life. The initial costs are born by the developer. Reduced expenditure at the outset can increase maintenance and replacement costs, which are likely to be more significant at later stages in the project life after the 25 year concession period and hence borne by the government. The balance is subject to negotiation and part of the concession agreement. Typically all large dams go through refurbishment cycles were electrical and mechanical equipment is upgraded and modernized. The assessment of the economics of dams may use
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a 50 to 100 year economic life. Most large dams exceed their economic life through cycles renovation and refurbishment. Figure 3.4 below presents an indicative time line of this phasing.13
Figure 3.4: Long‐term Phasing schedule for mainstream Mekong hydropower 2015 2020 2025 2030 2035 2040 2045 2050 2055 2060 2065 2070 2075 2080 2085
CONSTRUCTION
OPERATIONS (INVESTOR) BOT HANDOVER PERIOD OPERATONS (GOVERNMENT)
REFURBISHMENT, UPGRADE or MAINTENANCE DECOMMISSIONING END PROJECT COMPONENT/INFRASTRUCTURE END LIFE ECONOMIC LIFE
Note: Phasing above is based on a 50year life cycle which is consistent with the time frame used by MRC to compute capital recovery costs. Depending on the operations and maintenance strategies the projects may last for longer than 50years
3.2 REASONS BEHIND THE LMB MAINSTREAM HYDROPOWER PROPOSALS
The large annual discharge (505 km3) and fall (4,800m) of the Mekong River combine to produce a hydrological regime with a large energy budget. Over geologic time the Mekong system has reached a state of dynamic equilibrium which utilises this energy to transport; water, nutrients, sediment, organic matter, aquatic biota; and carry out other important ecosystem functions making the Mekong Basin one of the most biologically diverse in the world and one of the most productive in terms of fisheries and agriculture. Initially, attempts to harness the energy of the Mekong and its tributaries were localised and relatively small‐scale. From the 1950/60s hydropower storage reservoirs have been built on the tributaries of the Mekong River starting in Thailand.
The preference for storage‐type projects in the tributaries can be attributed to: (i) global experience with storage hydropower provided greater confidence in construction and operation techniques, and (ii) large reservoirs offered the ability to regulate stream flow allowing for a number of other benefits to human communities, including potential for multi‐purpose use (e.g. irrigation off‐takes form the reservoir), year‐ round water supply, control of dry season lows/droughts and wet season flooding.
13 For further information on the project economic life and actual operating life the World Commission on Dams (2000) report provides a view of issues such as refurbishment, repair and decommissioning.
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In the 1970/80s, the social and environmental impacts of hydropower with large storage reservoirs began to be better understood, especially in relation to the adverse effects of flow regulation and the inundation of large areas of land.14 This led to renewed interest in low head hydropower projects on the Mekong mainstream, which relied on the flow rather than storage head to generate electricity (Acres, 1994). In 1994, the Mekong Secretariat, United Nations Development Program and the Government of France undertook a study of the LMB Mekong mainstream to identify potential sites for low storage run‐of‐river projects. Eleven of the twelve projects considered in the SEA were considered in the 1994 study. Only Thakho which emerged as an alternative to Don Sahong is new. There are a number of engineering features of the LMB ‘run‐of‐river’ projects that make them attractive from an operation and power production point of view:
• Large power outputs: The large flows in the Mekong River allow each project to generate between 2,000‐12,000GWh/yr
• Short ramping rates: the projects can be brought online in a matter of minutes, compared to the much larger ramping rates for thermal power plants.
• Suitability for peaking: these ramping rates make peaking operation a possibility, which would allow operators to target energy production to times of the day when the buying price is highest
These projects were then de‐prioritized after the Acres Report (1994) because the large seasonal variability in Mekong flows and high sediment load of the river proved inhibitive to their feasibility as well as being unpopular with local communities. Three major developments in the basin have occurred since then which have out the LMB mainstream projects back on the table:
1. Upstream regulation of the flood pulse: changes to the hydrological regime from upstream hydropower development will disrupt the Mekong flood pulse and provide a more reliable year‐ round supply of water, increasing dry season flows by as much as 20% as far downstream as Kratie and as much as 50% at Kratie in the low flow months (Adamson, 2009).
2. Expected reduced sediment load: In the order of 40‐60% of the Mekong sediment load originates in Yunnan. The Yunnan cascade will have individual trapping efficiencies of up to 95% and combined trapping efficiency of approximately 80%, which has benefits from an operational, maintenance and risk failure point of view.
3. Continued growth in energy demand for the Mekong region (as detailed in the baseline report) and the introduction of the private sector as a development force. These factors have facilitated a shift from exploring a number of options to identify a small number of candidate projects to take through to operation (as was the case in 1994), to the current situation where all 12 projects are being explored individually by 12 different developers.
14 See for example studies on the impacts of the Nasser Dam on the Nile ecosystem, delta , fisheries and agricultural soil fertility: Welcome, R.L. 1985. River Fisheries. FAO Fisheries Technical Paper 262, or studies on the Mississippi River basin: Meade, R.H., and J.A. Moody 2009. Causes for the decline of suspended sediment discharge in the Mississippi River system, 1940 ‐2007. Hydrology Processes, vol 24, pp 35‐49.
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3.3 REGIONAL COOPERATION, THE MRC AND THE PNPCA PROCESS
Planning for mainstream hydropower development is moving forward mainly on a project by project basis without overarching national plans for the use of the Mekong River in any of the four LMB countries or without an agreed regional plan for the use of the Mekong. The mainstream projects do not appear in the Thai and Lao national power plans. Equally significant, planning is moving forward within the confines of one sector in each country – the power sector – with limited involvement of other users of the Mekong River – either development sectors or communities.
However, there are various development planning levels, which provide an opportunity to support decision makers in adequately considering the risks and opportunities and broad trade‐offs relating to the 12 projects in a river basin context. Central to these is the MRC BDP planning process. The SEA fits within these layers of planning and has the potential to contribute to each of them. The MRC Procedures for Notification, Prior Consultation and Agreement PNPCA established under the 1995 Mekong Agreement is one of the most significant regional instruments for consideration of mainstream hydropower power.15
MRC Procedures for Notification, Prior Consultation and Agreement: Article 2 of the 1995 Agreement on Cooperation for the Sustainable Development of the Mekong River Basin calls on signatory countries to promote, support, cooperate and coordinate in the development of the full potential of sustainable benefits to all riparian States and to prevent wasteful use of Mekong River Basin water.
In 2003, the LMB countries adopted Procedures for Notification, Prior Consultation and Agreement on uses of Mekong waters and related resources. That 2003 PNPCA Protocol and its 2005 Procedural Guidelines require Member States to notify each other through the MRC of proposed uses of the Mekong tributaries and mainstream so that the potential impacts on multi‐stakeholder rights and interests can be assessed and optimal water use determined. For the mainstream proposals, the MRCS must take a proactive role to assist the Joint Committee in assessing whether the use is reasonable and equitable, whether greater benefits can be derived through cooperation and trade‐offs and to ensure due diligence in the planning process. The PNPCA process requires that the Joint Committee aim to arrive at an agreement and issue a decision containing conditions relating to the proposed use (PCA 5.4.3.).
During 1995 to 2008 there were 28 notifications all relating to developments on tributaries. The MRC took little action other than informing Member States. In early 2009, the situation changed with respect to mainstream proposals where initial information on a number of mainstream dam proposals was submitted to MRCS by Lao PDR, Cambodia and Thailand. The consultation part of the PNPCA has yet to be triggered, though it is anticipated in 2010.
The MRCS was also instructed in 2008‐2009 by the Joint Committee to take two important steps to inform members and facilitate planning: (i) to conduct a strategic environmental assessment of all mainstream projects in the pipeline and, in parallel, (ii) to prepare Design Guidance for Mekong Mainstream Dams in the Lower Mekong Basin. Under the 1995 Mekong Agreement, the MRC needs to formulate a consistent approach to design and operation of mitigation measures of mainstream dams. Also, the Joint Committee
15 Other planning instruments are detailed in the SEA inception report and include: location project‐specific planning, (ii) national & sector development plans, (iii) bilateral transboundary project planning, MRC Basin Development Plan, and (Iv) GMS sector and economic corridor plans
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will need to refer to certain design considerations during the prior consultation process for mainstream dams. The guidance is project specific, while the SEA is to explore the broader economic, social and environmental system implications of the projects collectively.
During the Lao and Cambodia consultations on the scope of the SEA, government officials often asked “where does the SEA fit in with the national project planning and assessment process?” and “what authority does the SEA have – do Member States have to abide by its recommendations?” In response to those questions:
The Joint Committee will need to reach an agreed decision concerning the mainstream projects, individually and collectively.
The SEA (like the Design Guidance) is advisory in nature – it is intended to guide and help shape the Joint Committee’s considerations and decisions under the PNPCA process – that is its main function.
The SEA is not being conducted as a formal requirement under the 1995 MRC Agreement and Protocols. It is a pilot to explore the potential usefulness of the tool in regional development planning. More specifically as a tool when needed to support the Joint Committee fulfill its role in guiding reasonable and equitable use of the Mekong waters;
The SEA is not addressing an existing plan or one in preparation but a group of “feasible” project proposals for the same river;
The projects are all in the planning stages so, in principle, the SEA can contribute to national planning and decision making with respect to the individual projects – at the discretion of individual MRC Member States;
Most of the projects have not yet been subject to EIAs or any form of cumulative impact assessment under national procedures so the SEA can help shape the requirements for those more specific studies.
In addition, there are other planning platforms that can benefit from the SEA process and outcomes:
The MRC Basin Development Plan is under preparation – the SEA can contribute to that process.
National power development plans are under review and preparation therefore open to influence.
The GMS energy road map and strategy is now under review and revision, supported by the ADB GMS ‐ RETA No 6440, and therefore the SEA could have an input to that process.
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4 ENERGY & POWER
4.1 REGIONAL DISTRIBUTION OF POWER BENEFITS
4.1.1 OVERVIEW
Under the energy and power theme in the SEA baseline assessment, the policies and motivations for hydropower development that are embodied in LMB country power policies were explored, along with the country‐specific motivations for cross‐border power trade. The baseline assessment also looked closely at the drivers and trends for electricity demand growth, the role of demand‐side management in reducing the rate of demand growth, and the role of alternatives in the electricity supply mix considering the energy resource endowment of each country and current policies on fuel imports and power imports/exports. These issues and options were considered in the context of the energy resource base and the power development policy context for each LMB country, as well as the different viewpoints that have been expressed by the stakeholders in the open SEA consultation processes to date.
This impact assessment for the energy and power theme focuses mainly on the regional distribution of power benefits, on the impact of power sectors in each LMB country from a utility economics perspective of least‐cost supply and on physical infrastructure risk. The assessment is provided in mind of the scenarios used in the SEA assessment to integrate inputs from all the themes, namely:
The BDP 20‐year probable future scenario (PFS for the year 2030) with no LMB mainstream dams and with all LMB mainstream dams (with and with/out cases), and Three sensitivity cases that consider the 20‐yr PFS plus, o Only the Lao northern cascade of LMB mainstream dams (ecological zone 2) o Only the Lao middle reach group (ecological zone 3) o Only the Lower group (ecological zone 4)
4.1.2 DISTIBUTION OF POWER BENEFITS
The results of the calculations on the regional distribution of power benefits for these two main scenarios (the BDP 2030 probable future scenario with/ without LMB mainstream dams) and the three sensitivity cases are provided in Table 4.1. The data show how hydroelectric power supply from tributary and mainstream LMB dams would be distributed among power systems in the four LMB countries. Table 4.1 thus illustrates the power benefit side of the opportunities and risk equation.16 The other sections of this report assess in qualitative and quantitative terms the nature of the development opportunities and risks that LMB mainstream dams provide or pose in other sectors, as defined by the seven SEA themes.
16 The analysis is provided using the MRC Hydropower database that was employed also for the MRC BDP Scenario Assessment work. Thus the results on the estimation of power benefits (opportunities) are complementary with the MRC BDP.
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Table 4.1 Regional Distribution of LMB Power Benefits for the 20‐year Probable Future (with and without LMB mainstream dams) and sensitivity cases
LMB Regional POWER SUPPLY PR0JECTED POWER EXPORT PROJECT INVESTMENT Distribution (GWh/Year) (GWh/Year) ($USM)
SCENARIO1 CAM LAO THAI VIE TOTAL CAM LAO THAI VIE TOTAL CAM LAO THAI VIE TOTAL
2030‐20Y‐with MD 3,677 20,412 60,694 35,058 119,840 19,384 64,004 0 0 83,389 11,669 27,165 0 2,771 41,605 2030‐20Y‐w/o MD 1,703 9,038 26,206 16,346 53,293 1,618 28,571 0 0 30,189 1,268 11,857 0 2,771 15,896 2030‐20Y‐ MD in zone 2 only 1,703 12,287 50,558 21,240 85,787 1,618 57,816 0 0 59,434 1,268 22,031 0 2,771 26,070 2030‐20Y‐ zone 3 only 1,703 16,759 30,423 16,346 65,231 1,618 32,788 0 0 34,406 1,268 16,402 0 2,771 20,441 2030‐20Y‐ zone 4 only 3,677 9,441 32,126 30,164 75,408 19,384 30,542 0 0 49,927 11,669 12,447 0 2,771 26,886
LMB Regional GROSS BENEFIT OF SUPPLY GROSS EXPORT REVENUE NET OVERALL POWER BENEFIT Distribution ($USM/Year) Estimated ($USM/Year) ($USM/Year)
SCENARIO CAM LAO THAI VIE TOTAL CAM LAO THAI VIE TOTAL CAM LAO THAI VIE TOTAL
2030‐20Year with MD 782 3,555 5,284 2,559 12,179 1,250 4,676 0 0 5,926 722 5,272 832 834 7,659 2030‐20Y‐w/o MD 362 1,574 2,281 1,193 5,410 100 2,113 0 0 2,214 273 2,394 381 629 3,677 2030‐20Y‐ zone 2 only 362 2,140 4,401 1,550 8,453 100 4,219 0 0 4,319 273 3,958 699 682 5,613 2030‐20Y‐ zone 3 only 362 2,919 2,648 1,193 7,122 100 2,425 0 0 2,526 273 3,556 436 629 4,894 2030‐20Y‐ zone 4 only 782 1,644 2,797 2,201 7,424 1,250 2,259 0 0 3,509 722 2,546 459 780 4,506
Notes: 1 Scenarios are based on the MRC Basin Development Plan (BDP 20 year Probable Future ‐ 2030 snap shot) 2 Gross benefit of supply is based on avoided thermal costs in country where power is consumed
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The difference in net overall economic power benefit between the 20‐year probable future scenario with and without proposed LMB mainstream dams is about $US 3‐4 billion annually by 2030, discounted ($ 2010). The economic power benefit depends heavily on the future energy mix that is assumed. It can be seen from Table 4.1 that the net overall power benefit is greatest for Lao PDR in all cases. This is due to a combination of factors, including the fact that Lao PDR has the largest number of potential sites for hydropower development and the relative cost of power from the different mainstream schemes, as is discussed further in Section 1.2.1 that follows on supply curves.
4.1.3 OTHER HYDROPOWER‐RELATED IMPACTS
In the SEA baseline assessment report a number of non‐power impacts associated with hydropower development in the LMB and issues raised by SEA stakeholders were quantitatively assessed. These are impacts that can have a regional distribution across the LMB countries, and to some extent, the Greater Mekong Sub‐Region (GMS). These factors include (i) labor – i.e. direct job creation (ii) contracts for goods and services like construction and electrical and mechanical equipment, and (iii) the contribution of LMB hydropower to regional GHG emission reductions from the power sector by virtue of avoiding or off‐ setting thermal generation beyond what can be achieved by demand‐side management.
Table 4.2 illustrates the scale and regional distribution of two such factors: expected wages from direct job creation, and gross GHG emission avoidance for the two scenarios and three sensitivity cases.
Table 4.2: Regional Distribution of non‐power impacts: Jobs and thermal avoided emissions
TOTAL PRESENT VALUE OF DIRECT DIRECT JOBS - WAGES DURING LMB Regional 2,3 JOBS CONSTRUCTION Wages duting Constuction & Operation Distribution ($USM) ($USM)
S CENARIO 1 CAM LAO THAI VIE TOTAL CAM LAO THAI VIE TOTAL
2030-20Year with MD 2,769 7,484 0 754 11,007 3,334 9,012 0 909 13,254 2030-20Y-w/o MD 345 3,314 0 754 4,413 415 3,990 0 909 5,314 2030-20Y- zone 2 only 345 6,081 0 754 7,180 415 7,322 0 909 8,646 2030-20Y- zone 3 only 345 4,550 0 754 5,649 415 5,479 0 909 6,802 2030-20Y- zone 4 only 2,769 3,480 0 754 7,004 3,334 4,191 0 909 8,434
GHG EMIS S ION OFFS ET4
(Million Ton CO2/Year)
Ton/MWh by Country5 0.86 0.86 0.65 0.97 S CENARIO CAM LAO THAI VIE TOTAL
2030-20Year with MD 318393494 2030-20Y-w/o MD 1 8 17 16 42 2030-20Y- zone 2 only 111332165 2030-20Y- zone 3 only 14 20 1 16 52 2030-20Y- zone 4 only 82132961
Notes: 1 . Scenarios are based on the M RC Basin Development Plan (BDP 20 year Probable Future - 2030 snapshot) 2. Assumes wages only in the country where project is constructed (adjustments would be made for 2 LMB dams spanning Lao and T Excludes indirect jobs / wages such as from services, mechanical & electrical equipment manufacture/supply, etc. 3. SEA baseline report considers the split between local and foreign jobs mostly from the GMS region 4. Gross GHG based on avoided thermal generation in the country where power is consumed. This is different than net GHG impact, which subtracts or takes potential for GHG emissions from reservoirs into account (a contoversial topic where as yet there is no consensus on the level of potential emissions from reservoirs of various kinds. 5. Specific GHG emission factor base on power generation mix in each country (i.e., type of thermal supply offset)
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An integrated assessment of non‐power impacts is provided in other thematic sections of this report, notably in the economics and climate change sections.
4.2 REGIONAL PERSPECTIVE OF ELECTRICITY SECTOR IMPACT
4.2.1 HYDROELECTRIC SUPPLY CURVES
An introduction to the concept of hydropower economic supply curves and their relationship to energy demand and alternative energy supply cost is helpful to better understand the benefits and risks that the proposed LMB mainstream schemes pose for the power sectors of LMB countries.
Thermal power projects (natural gas, coal and oil‐based) can be replicated at the same cost and size almost indefinitely to meet electricity demand growth. The physical limitation is fuel availability, which depends on the primary energy resource endowment of the country and appetite for fuel imports. This replication of power stations is not possible with hydroelectric projects. Each hydropower site is unique. The cost and annual electrical energy produced is different for each site and there are many possible project configurations. Therefore, to compare the electrical generation potential and cost of different sets of hydroelectric projects it is useful to refer to the supply curve of each set.
The supply curve of a particular group or set of generation projects is a plot of electrical energy that is available below a certain cost level. Figure 4.1 shows the supply curves for two sets of LMB hydroelectric projects: One set corresponds to all new tributary and mainstream projects (i.e. projects that are planned or under construction) and the other set corresponds to all new tributary projects (i.e. excluding mainstream projects).17 In Figure 1, the horizontal axis corresponds to annual energy (supply or demand) expressed in terawatt‐hours.18 The vertical axis corresponds to energy cost expressed in US dollars per MWh, a common trade unit for wholesale power.19
Figure 4.1 also shows (using dashed arrows) the incremental annual electricity demand in Vietnam, Thailand, Cambodia and Laos that would be partially served by those projects. That is the annual demand in year 2025 that is not yet supplied by existing projects.20 The incremental demand of Laos and Cambodia is very small compared to that of Thailand and Vietnam and also with reference to the power potential of new hydroelectric projects. The height of each dashed arrow represents the energy cost of alternative thermal energy in each country. The alternative energy cost in Vietnam and Thailand is much lower than in Cambodia and Laos and in effect indicates the limit of energy cost for hydroelectric projects in Laos and Cambodia that could competitively export to those power markets.
17 The environment and social mitigation costs incorporated in the supply curve analysis are costs provided by project proponents. These estimates have not been submitted to formal EIA / SIA scrutiny in national systems and may not reflect transboundary considerations. 18 1 terawatt‐hour or TWh = 1 million megawatt‐hours or MWh 19 Some readers may be more familiar with energy cost expressed in US Cents per Kilowatt‐hour or KWh, the relationship is 1 USCts/KWh = 10$US/MWh 20 The individual Power Development Plans (PDPs) for GMS countries that were reviewed in the ADB RETA 2240 looking at regional power exchange, which is the basis for the considering the latest official forecasts in the LMB used in this SEA only provide load forecasts to 2025.
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The horizontal distance between the two supply curves gives the difference in energy potential for any given level of energy cost. Since the lowest alternative energy cost is that of Vietnam (i.e. $73 /MWh) it can be assumed, as a reference, that 70 $/MWh is a reasonable maximum viable energy cost of energy for export. At this cost level, the supply curve for tributary projects shows a potential to contribute approximately 32 TWh of annual energy. The supply curve for all projects shows a potential contribution of 97 TWh. Thus, the mainstream dams add 65 TWh of annual hydroelectric energy competitive against alternative forms of generation in export markets.
With this information it is possible to better explain the benefits and risks of mainstream projects to the different LMB national power sectors.
Figure 4.1 – Assessing the benefits of mainstream projects to the Power Sectors (supply curve)
4.2.2 HYDRO EXPORTING COUNTRIES
Cambodia and Lao PDR have very high alternative energy (thermal) costs and very small incremental electricity demand in relation to the potential scale and the cost of either set of hydroelectric projects (mainstream or tributary), as depicted by the supply curves in Figure 1. Thus, the differential energy potential and cost between tributary or mainstream developments is less important for supply in these smaller power systems.21 In other words, the Lao and Cambodia power sectors may be largely indifferent to whether hydropower is supplied by mainstream or tributary projects, except if the mainstream schemes are the only option to obtain the quantum of hydroelectric power needed.
To the extent that net revenue from hydropower exports can be reinvested in the power sectors of Cambodia and Laos, the difference in export revenue contributed by mainstream projects and tributary
21 At the same time shaving some form of hydropower supply is important as it implies a difference of two to four times in the cost of generation (thermal) to serve incremental demand.
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projects could greatly improve access to affordable electricity. This is particularly so in Cambodia, where the grid is more limited. However, it is unlikely that the full differential benefit can be realized until after the debt on the projects is repaid, which probably means some 20 years after their initial date of operation. More specific comment on this aspect would require an evaluation of the terms of concession and power purchase agreements. Most proposed projects are only at the feasibility study stage (MOU), which as described in the baseline assessment report is a very early in the regulatory process.
4.2.3 HYDRO IMPORTING COUNTRIES
In the power sectors of Thailand and Vietnam, the benefit of mainstream hydropower is derived from an inverse situation: low alternative energy cost (thermal) and high incremental electricity demand relative to the hydropower supply curves. As noted in the SEA baseline report, energy demand (GWh) in Vietnam and Thailand combined represents 96 % of LMB electricity demand. 22
Imports of power from LMB mainstream dams would only cover about 16 percent of the incremental annual demand of Thailand and Viet Nam. This contribution offers a cost saving of some 37 percent. Therefore at generation level, the main beneficial impact of power from LMB mainstream projects is to reduce the cost of incremental electrical energy supplied by about 6 percent. 23 Since generation is only about 50% of the cost of service to the final user (the rest is transmission and distribution costs), and since incremental demand growth is only about half of total demand, the actual benefit on total cost of service is probably in the order of 1.5%. This could still be very significant in absolute terms for the whole of the power sectors but unlikely to offer any major change the power utilities financial health, level of power services, or overall industrial competitiveness in the economy due to power supply.
4.3 IMPACT OF MAINSTREAM PROJECTS ON NATIONAL ENERGY POLICES
4.3.1 THAILAND AND VIETNAM
As the SEA baseline paper on the energy and power theme discusses several factors that shape national energy policies of LMB countries concerning cross‐border power trade and their appetite for power imports. One key consideration is that policymakers in Thailand and Vietnam have been progressively relaxing limits on tolerable dependence on levels of imported power in their respective power systems. This has also been reflected in the gradual increase in the quantum of power for cross‐border trade that is authorized under the bilateral power trade MOUs over the past decade between Lao PDR and Thailand (now 7,000 MW) and Loa PDR and Vietnam (now 5000 MW). Any continuation of this trend would enable an increasing proportion of imported hydropower from Cambodia and Laos.
22 Official demand projections from PDPs show that in both 2015 and 2025, energy demand (GWh) in Vietnam and Thailand combined will represent 96 % of LMB electricity demand. - Thailand: the power demand is projected to increase by a factor of 2.2 in the next 15 years, with an annual increase of peak demand of 2,600 MW per year in 2025 (equivalent to 3 new 800 MW gas‐fired plants per year). - Vietnam: will catch up with Thailand demand in 2014. The power demand is projected to increase by a factor of 3.7 in the next 15 years, with an annual increase of 4,600 MW per year in 2025 (equivalent to 6 new gas‐fired plants per year). 23 This excludes consideration of issues such as energy supply diversification, particularly important for the Thailand as the policy is to reduce dependence in natural gas as discussed in the baseline assessment.
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From the supply curves (in Figure 4.1) it can be seen that mainstream LMB projects account for two thirds of the potential quantum of electricity available to import. Such higher tolerance for power imports from hydropower from neighboring counties also lessens the urgency and role of imported coal and nuclear generation in the LMB. These are med‐ to longer‐term alternatives for large‐scale power supply, which are identified in Thailand and Vietnamese power development plans (PDP).24
In addition to cost, some observers feel these technologies (coal and nuclear) have disadvantages relative to hydro imports. This is in terms of strategic issues that range from public acceptance to international relations concerning reducing global GHG emissions (coal) to nuclear non‐proliferation questions. The potential of mainstream dams is only 16% of incremental demand in Thailand and Vietnam combined.
4.3.2 LAO PDR
Laos is an experienced hydro producer and has many tributary projects within a size range and energy costs comparable to those of mainstream projects. For example, Nam Theun 2 that has recently become operational has an installed capacity of 1070 MW. The average installed capacity of the nine proposed LMB mainstream dams in Lao PDR is 1085 MW, the largest being Ban Koum at 1,872 MW.
Figure 4.2 shows the supply curves corresponding to hydroelectric projects in Laos and relative to its incremental demand. There is a large potential to produce economical electrical energy for domestic supply and export, whether the LMB mainstream projects are included in the supply mix or not. These conditions suggest that even without a foreign partner or export agreement, Laos can probably find the means to finance sufficient hydroelectric capacity to meet domestic demand. In the absence of mainstream dams opportunities Laos would clearly continue with a strategy of hydroelectric development exploiting its large inventory of attractive tributary projects consistent with its policies.
Figure 4.2 ‐ Impact of Mainstream Projects in the Laos Power Sector
24 As discussed in the SEA working paper on the energy and power theme the recent PDPs of Thailand and Viet Nam and ADB RETA (6220) show that expansion of power generation from coal in the LMB will be primarily based on import of coal from outside the greater Mekong subregion.
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4.3.3 CAMBODIA
There are very important differences between the outlook of Laos and Cambodia without development of mainstream hydropower schemes in their respective territories. Those differences are well illustrated in Figure 4.2 and the corresponding graph for Cambodia shown in Figure 4‐3.
Firstly, note the position of the supply curve of tributary projects relative to the incremental electricity demand. The potential for Cambodia to develop tributary projects with an energy cost attractive for export is only 5 TWh, which is about half of the Cambodian incremental energy demand by 2025. Secondly, since Cambodia has almost no existing hydroelectric generation, not only is it necessary to provide for affordable supply to meet the incremental electricity demand, but also to replace existing demand now met by expensive diesel generation. The total demand is also shown in Figure 4‐3. It would need almost three times the energy potential of tributary projects to be met.
The supply curve with all projects shows that after meeting all the domestic demand with hydroelectric power from tributary and mainstream projects, there is only about 5 TWh that could go to export, compared to nearly 75 TWh of exportable power in Laos.
The implications therefore If Cambodia managed to develop its tributary projects for domestic supply only, that would only reduce it’s extremely high energy cost by some 30%. Without mainstream projects the only reasonable energy strategy would be to develop coal plants and compete with Thailand and Vietnam for hydropower imports from Laos, which would be difficult. In addition, any solution to Cambodia’s power demand requires a major expansion in the national grid.
Figure 4‐3 ‐ Impact of Mainstream Projects to Cambodia Power Sector
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4.4 POTENTIAL FOR COLLATERAL EFFECTS ON ELECTRICITY SECTORS
This section addresses two questions, namely: (i) could the large capital investments required for mainstream projects adversely affect other power sub‐sectors by diverting needed capital from them, and (ii) would the lower energy supply cost derived from mainstream dams reduce incentives for energy conservation through demand side management.
4.4.1 CAPITAL CONSTRAINTS
The magnitude of the equity investments and potential debt burden to develop the mainstream projects is probably beyond the possibilities of the power sectors of Cambodia and Laos as individual developers, even if supported by credible contracts with foreign off‐takers. These projects can only be developed jointly by the host country and the export market country (or conceivably a third party foreign investor) under a sophisticated financial and trade arrangement, which may even transcend the electricity sectors to involve commercial commitments of a bi‐lateral or regional nature.
For the Nam Theun 2 tributary hydropower project, Lao PDR negotiated a concessional loan to finance its equity contribution. Because this is a long‐term concessionary loan, the annually debt service payments are considerably less than the equity revenue Lao PDR receives. Thus there is no debt burden. Securing similar concessionary arrangements for LMB mainstream dams would likely be much more difficult for many reasons including perceptions of reputational risk for potential lenders due to the widely recognized controversial nature of the LMB mainstream proposals. Moreover, Information on how much equity and any consequent debt burden or relaxation of income taxes to finance debt is not available. It would make sense that the share of the burden on Cambodia or Laos would only be that warranted by the direct benefit to their power sectors. Therefore no negative impact should result from diverting cash flow from other development priorities. Naturally this assumes competent negotiation of development terms among all interested parties across the whole spectrum of financing considerations.
4.4.2 ADVERSE SIGNALS FOR ELECTRICITY CONSERVATION
The SEA baseline assessment reviewed the current status and trends in demand‐side management in the LMB. It focused on energy efficiency (EE) and demand‐side management (DSM) progress and potential in Thailand and Viet Nam because these are the main markets for LMB mainstream hydropower schemes. The main conclusion was, with current trends, DSM can sever to reduce the rate of electricity demand growth in the medium‐term to longer‐term. In Viet Nam in particular, many enabling conditions for DSM institutional arrangements have yet to be put in place and structural change is a long‐term proposition.
All things considered, electricity demand is elastic with respect to the electricity tariff. Therefore, a reduction in the tariff sends an adverse signal for EE behavior and undermines consumer support for various DSM measures. The effect of mainstream projects on Thailand and Vietnam power cost would be to reduce coats in the order of 1.5%. While at first glance some may consider this detrimental to DSM, the assessment of EE/DSM in the SEA baseline indicates clearly the importance of the electricity tariff level overall in establishing appropriate tariff / pricing signals for EE/DSM, as well as the need to have appropriate tariff structures and time of day pricing as well as the many practical factors that come in play
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to ensure electricity consumers in all sectors have real and improved access to energy efficient appliances/motors/ equipment by improving the supply chain.
In Cambodia, where the effect of reduced tariffs will be most noticeable here probably would be an increase in electricity consumption (per connection) if tariffs were to drop by 30% or more as a result of lower cost supply from mainstream projects. However, that will most likely mean more use of electricity for productive purposes because electricity prices, even significantly reduced from current levels will still be much higher than neighboring countries and high relative to average household income levels.
4.5 DESIGN AND OPERATING ASPECTS OF MAINSTREAM PROJECTS
4.5.1 PEAKING OPERATION
All mainstream projects have very limited potential to regulate the flow of the Mekong River because their water storage capacity is small in relation to their design discharge. In terms of potential for peaking operation the more likely order of projects is Luang Prabang, Sambor, Pakbeng, Xalaburi, Don Sahong and Sanakham. These plants could store enough water for several hours of operation at full discharge. Other LMB mainstream schemes have lower potential for peaking.
Nevertheless, during the dry season it is possible to operate most of the projects in such a way as to maximize generation during hours of high demand. However, regardless of final characteristics, there is nothing in the design of a hydroelectric project that prevents it from being operated at uniform discharge during all hours provided that the flow is not being modified upstream.
The regulatory authorities that deal with the use of water have the responsibility to determine tolerable variations in flow regime and reflect such constraints when the MOU or a license to develop a project is granted. Not doing so can result in sub‐optimal design and more expansive energy production.
4.5.2 CAPACITY FACTOR
The plant capacity factor is defined as the fraction of the installed capacity of a project that is expected to be utilized on average. The mainstream projects have a rather wide range of capacity factors from 0.32 (Sambor) to 0.63 (Don Sahong). This is intriguing for a group of projects that would have to harmonize their operation and cater to similar power markets.
The most likely reason for such differences is how developers have perceived the value of energy at the preliminary stage of design for all mainstream projects. Current designs and proposal have not yet been subject to the rigors of power purchase negotiation, and perhaps more important, securing project finance. It is at that stage that the real optimization of installed capacity (a key driver of cost) and hence capacity factor, often takes place. It is not uncommon for installed capacity to change quite drastically at more advanced levels of project design, after feasibility study. The final project may have very different capacity factors than those currently represented for projects at the feasibility study stage.
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4.5.3 POWER TRANSMISSION AND LOCAL POWER SUPPLY
Most of the power from any large hydro project, tributary or mainstream, goes into a project substation from where a transmission line takes it to the national interconnected grid or to regional grids for domestic supply and export. The transmission line from the project substation to the national grid usually has a voltage level (approximately 200 kV) that is lower than that of the primary grid (approximately 500 kV) but much higher than that of the distribution systems serving final users (anywhere between 5 to 20 KV). Since the regions near the Mekong River are more densely populated and more likely to be served by national or regional grids, the mainstream projects probably have less requirement for extensive high voltage transmission than tributary projects.
In addition to the bulk power injected to the high voltage grids, small amounts of power from the plant must be locally available to meet the demand of the power station and its resident staff. This is supplied directly from the substation by a dedicated low voltage local line. It is not uncommon that nearby communities, if not already connected to the national grid, be supplied by this low‐voltage line.
4.5.4 SAFETY OF MAINSTREAM DAMS – INFRASTUCTURE RISK
All dams represent a significant downstream risk where the potential for loss of life, economic loss and ecological damage from the failure of a dam is very large. LMB mainstream dams, while generally lower in height than tributary dams are no exception, since their failure can impact densely populated areas. Each developer of proposed LMB mainstream dams has designed structures for dam safety according to national regulations and regional practice. Reflecting the need for a consistent approach to dam safety among all LMB mainstream dams, the MRC recently developed detailed guidance for LMB country regulators and developers (MRC, 2009). This guidance is offered not only for the design stages, but also for the implementation and operation phases and is based on international best practice (Preliminary Design Guidance of Proposed LMB Mainstream Dams, Section 5, MRC, 2009).25
The MRC guidance suggests that dam safety is of paramount importance for the individual dams proposed as well as the safety of any cascade as a whole. It notes the broader philosophy behind good practice today is the safe design, construction and operation of dams depends on more than engineering factors. 26 In this respect, the approach to dam safety must recognize that failure of a dam is a complex process that can include human error in design, construction and operation, maintenance and monitoring stages of projects. A systematic approach and management framework that accounts for the complexities of operation of dams and ensures that the appropriate institutional and communication arrangement are in place is fundamental to achieve and assure dam safety. Emergency preparedness programs are also of fundamental importance to engage downstream communities. 27
25 See http://www.mrcmekong.org/download/free_download/Preliminary‐DG‐of‐LMB‐Mainstream‐dams‐ FinalVersion‐Sept09.pdf International standards include the World Bank Operational Policy 4.37: Safety of Dams and the International Commission on Large Dams (ICOLD) 26 Bulletin on Dam Safety Management, ICOLD, 2005 27 An emergency preparedness plan, specifies the roles and responsibilities of all parties when dam failure is considered imminent, or when expected operational flow releases threatened downstream life, property, or economic operations that depend on river flow levels. The plan itself is prepared during implementation and is in place before the projected initial filling of the reservoir. In particular, it is important to have a clear communication strategy to engage with stakeholders on dam safety issues and emergency preparedness activities that directly involve or affect them.
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There are different modes and degrees of severity of dam failure. These range from failure events that affect dam facilities, but leave the main structures intact, to actual structural failure of the dam itself.
From a design perspective, the safety of a dam is determined by a combination of factors including the magnitude of the flood event it can tolerate without risk of a catastrophic failure that could result in a devastating flood wave downstream. International organizations, engineering societies and local regulators establish strict guidelines on how such hydrological events should be selected and guidelines establish the probability of the flood event to be tolerated. Historically it was usually a 1‐10,000 year flood for any dam that posed a risk to populated areas.
The extreme events associated with such probabilities are derived from historical records of dams, but several decades ago it was realized that in the context of climatologic events, history is a not a reliable indicator of future behavior. Thus long before climate change became a household term a different criterion was established for the safe design of large dams in populated areas. This is based not in historical events, but on a hydro‐meteorological calculation of the worst possible flood event at a particular site called the Probable Maximum Flood or PMF. The PMF can result in designs of spillways, for example, that are more than double the size of design to 1:10,000 flood event.
It is important to note also that occurrence of a 1:10,000 or PMF flood event does not imply catastrophic failure of dam structures. Low‐head dams can be designed withstand being overtop if the spillway design capacity is exceeded, but there would often be significant damage to equipment. The power station may be out of operation for a considerable time. Where a flood were to exceed the spillway design capacity, and depending on the type of dam, the outcome may be only limited local damage that is overshadowed by the wider damage that occurs in flood channels as the river reached extreme flow levels. In practice, the low‐head Mekong LMB mainstream dams would certainly have to be designed to avoid complete failure.
One example of such failure is the largest dam failure incident in North American history. This occurred in Quebec, Canada in 1989 in the Saguenay River 28 in 1989 recorded as the largest overland flood in 20th century in the country’s history. In this case, eight dams were overtopped and thousands of people were displaced. No concrete dams or concrete rock‐fill dams failed, but embankment dams did. There was some loss of life, considerable economic loss and massive ecological damage that was sediment related. The major damage was due to the overwhelming impact of the occurrence of the 1:10,000 year flood.
Without a doubt, the highest priority for any agency responsible for regulating the development of LMB mainstream dams is to ensure that they all meet PMF criterion. Secondly, that the PMF is calculated at each site by the same methodology. In this respect the MRC’s Preliminary Design Guidance calls for this approach. With the adoption of international best practice there will be an expert dam safety panel for each dam that reviews designs and actions at each step in construction and operation. The actions at each stage will be measured for conformance to international best practice and open to public view and scrutiny. In addition, the MRC’s PDG identifies the need to evaluate the safety of the entire cascade of proposed LMB mainstream dams and the need for coordination and accountability arrangements for operation stages, if more than one LMB mainstream dam is eventually built.
28 http://www.canadiangeographic.ca/magazine/ma97/feature_saguenay_floods1.asp
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4.6 MAINSTREAM HYDROPOWER DEVELOPMENT PLANNING
The nature of the current development of hydropower in the LMB that involves soliciting private sector investment can be characterized as "opportunistic" in the sense that a potential developer negotiates directly with the licensing authority on the available sites, and subsequently, all developers (in many respects concerning the LMB mainstream dams) compete to be the first project to be approved. This is against the background of less certainty when the “second” or subsequent mainstream project would be approved as such projects depend on market conditions.
Hydropower development in this context does not necessarily follow a prescribed plan of river basin optimization and strict economic merit. Rather it moves in response to the interest expressed by developers through initial MOUs that are a form of proxies to formal development licenses. In many respects this is not very different to what happens in other hydroelectric markets in the world that have more structured sets of regulations, licensing procedures and power pricing mechanisms. In those settings the benefits of river basin optimization can be set aside in the quest to attract foreign investors to this capital intensive industry.
However, in the view of many the implications of Mekong LMB mainstream projects are too significant for opportunism to be the main determining factor in this case. The scale of these projects, the transboundary nature of their areas of influence and the uncertainties about their physical, social, environmental and economic impacts all call for a more cautious and rationale approach.
There is ample room for optimism about the evolution of practices in the LMB. For example, after the LMB mainstream sites were studied (Acres Report, 1994), the 1995 Mekong Agreement was signed. The 1995 Agreement embodies the basin development plan (BDP) that looks at the development of hydropower in river basin context based on IWRM principles. The proposed LMB mainstream projects are also subject to Procedures under the 1995 Agreement, notably the PNPCA. At this time (2010) only the feasibility and EIA/SIA studies of mainstream proposals have been undertaken, or are at various stages of preparation. Moreover, this SEA is another example of MRC consideration of the mainstream proposals in a river basin context that will eventually inform the MRC PNPCA procedure, if and when it is triggered.
4.7 CONCLUSIONS REGARDING POWER SECTOR IMPACT
Mainstream hydroelectric projects in Laos and Cambodia represent roughly two thirds of the total energy potential of hydroelectric projects identified in the LMB not yet operating or undergoing firm development.
The overall power benefits to LMB countries are significant. The difference in net overall economic power benefit between the 20‐year probable future scenario with and without proposed LMB mainstream dams is about $US 4 billion annually by 2030. It can be seen the greatest beneficiary is Lao PDR, in all cases (table 4.1).
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Despite the fact that the energy from mainstream projects would be used regionally and setting aside considerations of energy supply diversity and export earnings, from a power supply perspective and the consideration of alternatives the development of mainstream projects more critical to the power sector of Cambodia.
Several circumstances determine that the two mainstream projects in Cambodia (Sambor and Stung Treng) are important to Cambodia’s power sector from a power supply perspective. Firstly, Cambodia has a very expensive generation system almost entirely dependent on imported oil. Thus, not only does Cambodia have to provide affordable power to meet incremental demand, but it also needs to replace its existing generation as much as possible. Secondly, Cambodia has a very small inventory of attractive tributary projects. The energy potential of these projects is not sufficient to meet incremental demands, let alone replace existing generation or export. Thirdly, Cambodia has virtually no experience in hydroelectric development or operation and thus will rely much more than Laos on foreign partnerships, which can only be attracted by mainstream projects that can enable power exports.
It may be argued that the scale of electricity demand in Thailand and Vietnam and the cost of alternative forms of power supply (thermal) are such that development of LMB mainstream projects would have a minor impact on electricity prices, and not radically alter the energy supply strategies of those countries ‐ applying least‐cost criteria alone.
For Lao PDR, the large inventory of economically attractive tributary projects means that the Lao hydroelectric industry can develop tributary projects for domestic use and export can continue at a healthy pace without mainstream projects. Nevertheless, the potential scale of annual export earnings would be significantly reduced, as shown previously in table 4.1 and the advantages of investing in stable and low‐cost power supply on future especially when concession terms are completed would be forgone.
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5 ECONOMIC SYSTEMS
Theme and key strategic issues
Key issues (relevant to hydropower) 1. What are the broad national and regional economic implications of large scale natural resource based development in the LMB countries? 2. What are the economic costs and benefits of sectoral development in the LMB countries? 3. What is the distribution of economic benefits between different areas, groups and sectors?
5.1 SUMMARY OF PAST AND FUTURE TRENDS WITHOUT LMB MAINSTREAM DAMS
Three main areas pertinent to mainstream hydropower development were identified in the baseline economics analysis. These were macroeconomic implications of large‐scale natural resource development in the LMB, sectoral economic trends in the LMB and distributional trends in the LMB.
Macro‐economic opportunities and risks relate to the large scale and rapidly increasing levels of investment in natural resources (i.e. hydropower, mining and plantation development) in particular in Lao PDR (and possibly Cambodia). This investment is largely composed of FDI. On one hand, this potentially represents a significant boost for this small economy crowding in investment and increasing consumption across a number of sectors. Conversely, such rapid growth in these sectors potentially poses a risk to competing sectors through driving up relative price levels resulting in exchange rate appreciation. This has the potential to reduce the internal and external competitiveness of other sectors in the economy (such as agriculture and manufacturing). The baseline analysis also noted potential fiscal implications of increasing government debt burdens in Lao PDR as a result of funding the purchase of equity in hydropower projects. This greater debt burden needs to be balanced against greater government revenues generated from hydropower development.
The sectoral analysis examined economic trends in fisheries, agriculture, construction, navigation, tourism, forestry, mining and industrial sectors and also looked at values of key environmental assets including aquatic plants, wetlands, flood control and saline intrusion control. In general sectors based on biotic natural resources are stable or in decline, whereas industrial use of natural resources and related sectors is expanding rapidly.
The distributional analysis found that while overall population was likely to grow, rural populations in the basin were likely to remain relatively stable despite high natural growth rates as rapid rural‐urban migration continues. Poverty rates in the basin are higher in remote upland areas and lower closer to the main stream and in larger urban settlements. Nevertheless, as population densities are low in upland areas the absolute numbers of poor are greater closer to the mainstream and in urban areas. This trend is increasing with rural‐urban migration driven by declining natural resources bases in upland areas and increasing employment opportunities in lowland and urban areas. Despite rapid growth in industry and service sectors in terms of employment and livelihoods for agriculture and fisheries remain important for rural livelihoods across the basin.
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5.2 EXPECTED MACRO ECONOMIC TRENDS WITH MAINSTREAM DAM CONSTRUCTION
As noted in the baseline analysis, according to available data (from IKMP at MRC) investment in hydropower over the last two decades has been expanding rapidly. From 1990 to 2008 an estimated USD 6.6 billion was invested in hydropower development in the LMB. Excluding mainstream dams from 2009‐2016 the investment figure is expected to reach USD 9.1 billion. The proposed investment in mainstream hydropower projects, which are all large projects would add an estimated USD 19 billion between 2016 and 2029 – more than double previous and other proposed hydropower investment in the LMB. In terms of annual average investment in hydropower this represents an increase from USD 365 million a year between 1990‐2008, to an expected USD 1,296 million a year between 2009‐2016, an increase of over 350%.
Mainstream hydropower development would imply an even larger additional investment for the period of 2016‐ 2029 of USD 1,450 million a year. Figure 1 below gives an estimated investment schedule for hydropower development in the LMB. Most of the funding for these developments, with the exception of any state held equity (which itself would need to be funded through increased borrowing), is expected to come from sources external to Cambodia and Lao PDR.
Figure 5.1: Estimated annual investment in LMB hydropower 2004‐2029
Source: ICEM based on IKMP hydropower database, MRCS
In general the macro‐economic impacts of mainstream dam development are likely to represent a continuation and increase of both the risks and opportunities identified in the economics baseline. This assumes that changes that take place will generally be proportionate to the investment made. It should also be noted that net government revenues from hydropower are likely to be significant in the context of these small economies, although it is not possible to estimate these figures without more information on project financing structures.
The development of MSHP may not represent investment which is additional to what would otherwise have been the case (for example tributary dams, thermal generation or mining investments). Therefore we need to bear in mind that some of what is identified here as the ‘impact’ of MSHP development may have taken place without
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these developments. Nevertheless, due to the scale and proposed schedule for these projects to some extent at least these impacts can be attributable to MSHP development.
MULTIPLIER EFFECTS DUE TO INVESTMENT STIMULUS
Any economic stimulus effects are unlikely to be qualitatively different from those felt as a result of other large scale FDI investment in the region. However, any multiplier effects will be correspondingly larger due to the size of these developments. As with other hydropower development the extent to which development of these projects acts as a stimulus depends upon how much of the investment capital results in local consumption. While some construction workers and materials are likely to be sourced relatively locally, in most projects turbines and other complex engineering is likely to be imported, in most cases skilled labour will also be imported. Although figures are not available it is likely that most of the investment capital is used purchasing goods and labour from outside the LMB and frequently from outside LMB countries (for example, importing turbines from China).
REAL EXCHANGE‐RATE APPRECIATION AND ‘BOOMING SECTOR’ EFFECTS
The added magnitude of FDI and foreign exchange earnings from hydropower if not managed in a financially prudent manner may imply risks related to real exchange rate appreciation caused by inflationary pressures in non‐tradable goods sectors. This is essentially the wider implications of the stimulus – or multiplier – effect of the proposed investment. The magnitude of this effect will depend on the extent to which these projects are ‘pass through’ or ‘enclave’ projects which source inputs and receive investment from outside the host country. Indications are that these projects are likely to be largely ‘enclave projects’, meaning the proportion of the investment capital being used to purchase goods in the host country will be limited. This is likely to limit positive stimulus effect, but will also mean that the prospect of macro‐economic imbalances emerging due to real exchange rate appreciation should be limited.
Nevertheless, these developments are likely to generate net revenues for the host governments. The size of these revenue streams will depend upon the PPAs and the details of the financing agreement for each of these developments. The amount of next revenue generated for the host governments over the period is therefore unclear. However, NT2, for example is expected to generate on average USD 70 million/year between 2010 and 202529. In the context of a small country like Lao PDR these revenues are likely to be significant, especially if a number of the proposed developments go ahead. The extent to which these revenues are likely to result in real exchange rate appreciation, or alternatively are used to ameliorate the negative impacts of real exchange rate appreciation on other tradable goods sectors will depend upon how the host government chooses to manage this revenue. There are two important aspects of this firstly, the extent to which the government has the capacity to manage these revenues, and secondly, the extent to which the host governments are under pressure to disperse these funds for various programmes which are unlikely to be of benefit to the tradable goods sectors and in fact represent expenditures which may lead to exchange rate appreciation. Thus it is difficult to draw definitive conclusions regarding the possibility of this effect.
It is also important to note that if any real exchange rate appreciation takes place it is likely to have negative distributional consequences as sectors which are most likely to be adversely affected by this phenomenon are just
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those which are of long term importance for poverty reduction, in particular the agricultural and manufacturing sectors.
PUBLIC DEBT SUSTAINABILITY IN LAO PDR
Host governments are likely to take an equity stake in these proposed hydropower developments. This will imply raising the national debt burden. Even if, as in the case of NT2, this debt is not sovereign guaranteed debt and is secured on the basis of the PPA, some state body will necessarily have at least some liability for this debt – even if this is minimized. In respect of debt sustainability, the significance of the proposed developments lies in the extra magnitude of debt they imply and to what extent any additional debt burden is likely to be off‐set by state revenues generated by these projects. This will depend upon the structure of each individual project’s finance for which there is little available information at present.
CONCLUSIONS
The proposed hydropower developments do not represent a qualitative divergence from the macro economic issues described in the baseline report. Rather the proposed developments will represent a much higher magnitude of investment meaning the financial opportunities and risks are also likely to be much larger. The opportunities offered by these developments in terms of i) economic stimulus; and, ii) revenue generation – while depending upon project details – are relatively clear. The extent to which negative impacts through exchange rate appreciation and debt sustainability are likely to pose a problem will depend on the state management of the macro‐economy and revenues generated from hydropower development. This will in turn be dependent upon both the political will and administrative capacity30 of the governments to manage the economy such that it maximizes these benefits. This is closely related to overall mitigation measures and will be discussed in the mitigation, avoidance and enhancement section of the SEA.
Moreover, as the power paper points out, the outcome of any agreement reached between off‐take countries, host countries and developers will depend upon not just economic factors but also geopolitical considerations, and importantly the capacity of host governments to negotiate an agreement that is likely to be favorable to the host country. It is therefore not a foregone conclusion that, from a macro‐economic and financial that the impact of these projects will necessarily be benign for all sectors of the economy.
5.3 EXPECTED SECTORAL EFFECTS ON ECONOMIC TRENDS
Mainstream hydropower development is likely to have wide ranging effects across a number of economic sectors, economic assets and ecosystem services.
ECONOMIC SECTORS
A number of sectors are likely to be significantly affected by mainstream dam construction. Sectors which are likely to experience significant impacts include fisheries, agriculture and forestry, tourism, navigation, construction, and mining and industry sectors. The likely impacts of the mainstream hydropower developments to these sectors
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have been estimated where adequate information has been available in terms of changes in output. For example, for paddy production losses and gains due to the developments have been included. Greater analysis of these changes is included in each sectoral theme paper.
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Table 5.1: Overview of economic risks and opportunities in key sectors Description Indicative values Cause of loss/gain Net loss/gain due to MSHP development Future trends with MSHP (narrative) Fish migration routes will be blocked and flood pulses will be disrupted, decline in fish populations likely to result. This is likely to be ‐700,000 to ‐1.4 million tonnes true both for migratory species and species Fish Loss (capture fisheries) USD 0.68/kg = USD 680/tonne which depend upon flood plains for Some of ‐USD 476 million to ‐USD 956 million this loss may be off‐set by the introduction of Fisheries reservoir aquaculture but potential yields from this remain highly uncertain. 25,000 to 250,000 tonnes (63,000 most likely) Gain USD 680/tonne (reservoir fisheries) USD 17 million to USD 170 million (USD 42.8 million most likely) ‐54% of river bank gardens loss in zones 2,3 Loss of river bank gardens due to inundation Riverbank garden production Loss (riverbank gardens) and 4 of long stretches of the mainstream river in USD 18 million ‐ USD 57 million/year zones 2, 3 and 4. Relatively small losses from inundation of ‐ 7,962 ha of paddy Loss (inundated paddy and transmission paddy more than offset by gains resulting Paddy production ‐ 22,475 tonnes of rice/year lines) from increased irrigation associated with ‐ USD 4.1 million/year mainstream hydropower development. Any reduction in sediment load and flooding will lead to a decrease in associated nutrient Agriculture and forestry replenishment. It is not clear that the Loss (value of nutrients to agriculture) N/A mainstream dams will effect agricultural production relative to the effects which are likely to be felt due to mainstream Chinese projects and tributary projects. Irrigation projects associated with the 17,866 ha of paddy hydropower developments are likely to Gain(increased irrigation) 77,701 tonnes of rice/year improve land productivity and rice USD 15.54 million/year production in some areas.
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Some valuable environmental assets upon which burgeoning ecotourism industry is Tourism revenues Loss (degradation of natural resource base) N/A based will be degraded or lost due to changes in the hydrology and ecology of the Tourism mainstream resulting from these projects. Large hydro‐electricity projects often attract Gain (HP project viewing) N/A (mainly domestic) tourism (for example Hoa Binh dam in northern Vietnam) Mainstream hydropower is likely to increase the navigability of the river as it will increase the depth of the river along significant stretches. However, this will be dependent Freight transport Gain (increased navigability) N/A upon designing dams such that they allow navigation. Which projects go ahead will Navigation affect the overall navigability of the river. Therefore, impacts on navigability and are dependent upon dam design Passenger transport Gain (increased navigability) N/A Even with navigation locks these projects will Loss (decreased longitudinal connectivity) N/A increase the time taken and probable costs of navigation Construction Sand and gravel extraction output Loss (reduced sediment load) N/A Unlikely to be significant in the short term. Changes in mainstream habitats will increase Aquatic plants Subsistence Loss (loss of habitat) N/A loss of currently economically important aquatic plants. Clean water supply, plants for food and Most of the in‐stream wetlands will be lost in medicines, fuel wood, nutrient recycling, between USD 3.36 million and USD 6.72 zones 2, 3 and 4 with significant impacts on Wetlands water purification wildlife habitats Loss (due to reservoir creation) million per year (2000 prices) their productivity and the in all likelihood groundwater recharge, flood control, carbon other ecosystem services they provide. sequestration, storm protection etc Source: All figures are derived from baseline and thematic papers
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ASSESTS
A range of fixed assets in and around the mainstream will be directly and indirectly affected by the development of the proposed mainstream hydropower projects. Fixed assets likely to be affected by hydropower development include the following:
• Houses and commercial property
• Residential infrastructure (water supply, electricity supply, waste water facilities etc)
• Industrial facilities
• Amenities and social infrastructure (schools, clinics etc)
• Roads and land transport infrastructure
• Moorings and docks
• Irrigation pumps and irrigation infrastructure31
• Land (agricultural and forestry)
The social theme paper outlines the impacts in terms of population and households resettled, which reflect the current best estimates available at 63,112 people to be resettled in 6,847 households. Assuming that each household has a separate dwelling, this means 6,847 houses will need to be replaced due to the proposed development.
Associated with the inundation of housing and settlements in impoundment area residential infrastructure and other amenities are also likely to be adversely affected. This includes electricity and water supplies, any waste water facilities and roads, as well as public amenities such as schools, clinics and government offices. In some places there are also industrial facilities close to the river – positioned to take advantage of river transport. For example, there are numerous saw mills on the river in and around Pak Lai, many of these facilities are likely to be affected by raised water levels. These costs will be significant although at present no valuation data is available.
Infrastructure actually in or on the river such as irrigation pumps and boat docks and moorings will also be affected. In this case the effects are likely to go beyond the upstream impoundment areas of the dams and also have effects down‐stream due to changes in water level and sedimentation. In the case of irrigation pumps there are generally three types. Free‐floating irrigation pumps placed on small wooden pontoons while allow the pump to access water throughout the year. While these pumps are common they typically small and provide water to a small local area. Other irrigation pumps are fixed upon the river bank and can be moved up or down depending on the water level in the river. Finally, the larger irrigation facilities are generally fixed and have a fixed inlet in the river. These last two types of irrigation pump are likely to need relocating as a result of hydrological changes resulting from dam construction. Up‐stream facilities may be inundated; others may need to have their intakes modified to make better use of changed hydrological conditions. Down‐stream fixed irrigation pumps may be subject to greater
31 These are likely to be largely off‐set by improvements in irrigation in the impoundment areas.
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levels of erosion or deposition of sediments and need to be altered accordingly. If the dams are managed to provide peaking power changes in water levels on a daily basis will mean that irrigation systems may have to be managed differently. However, in the case of irrigation, more stable water levels in impoundment areas.
Similarly, navigation infrastructure, and in particular docks and moorings for boats will be affected. Up‐ stream some moorings and docks are likely to be inundated and will need to be reconstructed at a higher level. Depending on the management of the dams (i.e. if the water is drawn down in dry season to provide peaking power supplies) this may mean that for part of the day some of these facilities may not be accessible. Down‐stream facilities may be subject to daily fluctuations in water levels (depending on the management of the projects) and changes in geomorphology including increased deposition in some areas and increased erosion in others, implying a need for remedial action (dredging to allow channel navigability or rip‐wrap protection for facilities subject to erosion) (see hydrology theme).
In general changes in the deposition and erosion of sediments due to the construction of the dams will mean significant changes to the geomorphology of the river. Together with the possibility of daily fluctuation in river levels due to management of the projects for peaking power, there is likely to be implications for all kinds of infrastructure in and one the river as well as assets based near the river which may be effected by declines in bank stability. This is likely to imply either the loss of assets or costs implied by improving protection around vulnerable locations.
Finally, there is likely to be significant land lost in impoundment areas due to rising water levels. The terrestrial paper estimates the amount of land likely to be lost, these results are reported below. While the areas of land lost are not high relative to other hydropower projects which can have large impoundment areas, in some areas this composes a significant proportion of the available land, for example in zone 2, where much of the suitable agricultural land is close to the mainstream. This means that land loss may have a disproportionate effect on populations in this areas as alternative land is not available.
Table 5.2: Land inundated due to mainstream hydropower development
Land use type Sq Km Value Paddy field 50.9 Data not yet available Orchard 1.8 Field crop 8.6 Swidden cultivation 2.2 Total cultivated 63.3 Bamboo forest 34.7 Deciduous forest 264.4 Evergreen forest 244.4 Total forest cover 543.5 Barren land 3.7 Grassland 23.8 Shrub land 0.9 Total open land 28.4 Built up area 1.8
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Source: ICEM
ECOSYSTEM SERVICES The baseline report mentioned two key ecological services related to mainstream flows – saline intrusion control and flood control. These both imply important, if hitherto unquantified, economic values. However, the hydrology analysis suggests that the impacts of mainstream hydropower development on these services will be limited. Flow rates in the dry season will be effectively unchanged by mainstream development meaning they will imply no improvement in the control of saline intrusion. Wet season flooding will be slightly reduced, however, this change is marginal and there is inadequate information to enable this effect to be quantified.
The third area of ecosystem services that was considered in the baseline were those services provided by the wetlands which include clean water supply, plants for food and medicines, fuel wood, nutrient recycling, water purification wildlife habitats groundwater recharge, flood control, carbon sequestration and storm protection amongst other things. Values for the wetlands were adopted from a transfer pricing exercise conducted in the by Schyut and Brander (2004), and arrived at an estimated value of USD 11.2 million/year (2000 prices). GIS analysis conducted for the aquatic systems paper suggests that the primary productivity of wetlands in the mainstream may be reduced by between 30 and 60%. Given that this calculation is based on the surface area of wetlands lost due to mainstream hydropower development, it is safe to assume that affected wetlands will not be able to perform their other services when so affected. Therefore, we can assume that service values in this exercise are reduced by a similar amount, meaning the loss of wetlands due to mainstream hydropower development is estimated to be between USD 3.36 million and USD 6.72 million per year (2000 prices).
5.4 EXPECTED DISTRIBUTIONAL EFFECTS ON ECONOMIC TRENDS
The economic costs and benefits of the proposed developments will not be borne equally by all groups or in all locations in the LMB countries. This section examines the distribution of economic opportunities and risks associated with mainstream hydropower development across different groups and areas in the LMB. The distribution of benefits are examined in a number of different dimensions including geographical location, social group and urbanization level.
5.4.1 DISTRIBUTIONAL EFFECTS BETWEEN RURAL AND URBAN AREAS
Opportunities and risks are likely to be unevenly distributed between rural and urban areas. However, both urban and rural areas are likely to realize opportunities and risks as a result of mainstream hydropower development. Urban and peri‐urban areas which contain most of the manufacturing industries (such as the Bangkok and the surrounding areas in Thailand, Phnom Penh and Shinoukville in Cambodia and the South Eastern region around Ho chi Minh City in Vietnam), will be those that reap the benefits of cheaper and more reliable electricity (especially in the case of Cambodia where expensive electricity has been identified as a key barrier to competitiveness (see power theme paper and IMF 2009)). However, this benefit should not be overstated as in the case of Vietnam and Thailand power demand would be met through other forms of generation, even if costs were slightly higher given the
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small portion of over power supply the mainstream dams would account for, this would likely have a very small impact on power price (see power theme paper).
Rural communities are unlikely to reap significant economic benefits from improvements in the power supply. While local communities may see the extension of electricity grids, in the immediate vicinity of the hydropower projects, project development is unlikely to have any significant effect on direct access to power supply for the more general rural population.
The section on potential macro‐economic impacts of mainstream hydropower development – focusing mainly on Lao PDR ‐ stresses uncertainty over whether potential macro‐economic risks will be realized. Nevertheless, if ‘booming sector’ effects are experienced this is likely to have a differential impact on rural and urban populations. In particular, non‐tradable sectors (i.e. services) usually concentrated in urban areas are likely to perform better than sectors that compete with the booming sector or sectors that compete with imported goods. Conversely, the manufacturing sector, also based in urban areas may suffer from declining competitiveness. Rural areas may see a decline in the relative value of their agricultural and other products, posing a possible economic risk. Without undertaking a comprehensive and detailed modeling exercise it is not possible to evaluate the impact on different sectors – and therefore differential impacts on rural and urban areas. Moreover, it is not clear that this effect can be ascribed to mainstream developments as any large capital developments are likely to imply similar effects.
Finally, rural livelihoods are at much greater risk than urban livelihoods. As the analysis in the economics, social and fisheries paper have shown, rural livelihoods within the LMB are still largely dependent upon the natural resource base. Throughout the basin, household rely on capture fisheries, agriculture (irrigated rice, rain fed rice, field crops and swidden agriculture), NTFPs and a number of other natural resource based activities, or ancillary services associated with them (e.g. boat and fishing net manufacture (see economic baseline paper)) for their livelihoods. In contrast urban dwellers tend to rely more heavily on industrial and service sector employment32. This in turn means that any direct impacts of mainstream dam development such as the expected depletion of fisheries, are likely to be borne predominantly by the rural populations. However, these impacts may lead to secondary effects such as increased rural‐urban migration as the depletion of the natural resource and increasing attenuation of rural livelihoods will constitute a significant push‐factor in the decision to migrate to urban areas. This may, in turn, lead to increased urban poverty levels. Moreover, it is not clear how fish price levels will respond to depletion of fish stocks. A significant increase in price may affect urban and rural dwellers alike. In fact the urban poor may suffer more than rural populations in the event of increased food prices due to mainstream hydropower development.
5.4.2 DISTRIBUTIONAL IMPACTS: POOR AND NON‐POOR
Likely distributional impacts of the mainstream hydropower development are also likely to be unevenly distributed between the poor and non‐poor. As the baseline report has shown poverty rates and distributions vary across the LMB. Higher poverty rates are usually found in remote up‐land areas away
32 It should be noted that in some areas (for example the Mekong Delta), much of the manufacturing industry is dependent upon locally produced natural resources (e.g. the rive processing industry), so this distinction is not as clear cut as it may at first seem.
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from the mainstream, however, higher population densities mean that the absolute number of poor is higher in low‐land areas closer to the mainstream. This trend has been increasing as increasing livelihood opportunities develop in low‐land (and associated urban areas) coupled with the depletion of the natural resource base and attenuation of associated livelihoods in upland areas. While it is not possible to project poverty rate or distributions to 2030, these trends are, in all likelihood, expected to continue. Moreover, while overall poverty rates are expected to decline, poverty and increasing inequality is likely to remain a problem.
The poor tend to be more vulnerable to adverse changes in environmental conditions because they have fewer assets, savings, skills and knowledge that can allow them flexibility in making necessary changes to their livelihood strategies in response to changes in environmental conditions. In the case of mainstream hydropower development the expected loss of fisheries is likely to be key impact on the poor. It is difficult to estimate the importance of fisheries to the poor in the LMB, in Cambodia it has been estimated that over 1 million people who in some way depend on these at risk fisheries (see social theme paper), however there is no information available indicating what proportion of them are poor. Assuming that the poverty rate amongst this group is the same as nationally, this means around 40% or 400,000 poor fisher folk’s livelihoods are at risk. As most fisher‐folk are from areas where poverty rates tend to be above the national average it is safe to assume that (with the possible exception of Lao PDR where upland areas are some of the poorest), amongst fisher‐folk poverty rates are higher than national averages. Moreover, analysis in the baseline fisheries, economics and social assessment papers indicates that LMB populations are highly dependent upon fish as a source of protein. Meaning that aside from providing employment, this resource is also important from a consumption and nutritional perspective. Given the extent of the expected reduction in fisheries, it is likely to have a significant impact on the nutritional status of the poor as they currently depend proportionately more on fish (and other aquatic animal) consumption than other groups and they are likely to be unable to diversify their consumption away to other food sources easily. The urban poor may be particularly at risk from any impact resulting in an increase in food price. This may be exasperated by increases in urban poverty due increased migration from rural areas due to the declining natural resource base there.
In contrast the non‐poor are not only less likely to be affected by the loss of capture fisheries, if they are, they are likely to be better able to cope with this loss as they have greater access to assets and resources.
5.4.3 DISTRIBUTIONAL IMPACTS: ECOLOGICAL ZONE
Impacts of mainstream hydropower development are also likely to be differentiated by ecological zone. This section looks at the probable distribution of those impacts by zone.
An estimated 77% of the 795km of zone 2 running from Chiang Saen to Vientiane will be effectively be a reservoir if the proposed developments go ahead. This will imply direct economic losses of a similar proportion of the wetland and their services in this area. Mainstream dam development in this zone will mean over 32,000 people will be resettled and nearly 76,000 directly affected33 (see social impact assessment). Land and river bank gardens inundated in this zone will be of particular relevance as other suitable agricultural land in the area for potential replacement purposes is limited. While population density here is relatively low, in some areas of the Lao PDR side of the river there are communities which
33 These are conservative estimates by developers based upon estimates of populations who loose land . assets or other livelihood resources – excluding fisheries (see social theme paper).
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are highly dependent upon river resources although for much of the population in these areas upland agriculture is the predominant livelihood source. Poverty rates in Oudomaxai are relatively high but those in Xayabuory are quite low. On the Thai side of the zone livelihoods are more diversified apart from amongst certain river dependant groups, while poverty rate is lower than in Lao PDR. The expected change in the ecological systems due to hydropower development will have greater impact on those river dependant populations in these zones, and higher poverty amongst some groups will result in greater vulnerability to these changes.
Zone 3 running from Vientiane to Pakse is significantly more populous than zone 2. The mainstream dams in this stretch of the river are expected to create impoundments for 159Km, or 22% of its length. In this area at least 935 people will be resettled34 and 2,570 people will be directly affected. In the Lao PDR area of this zone populations dependent on fish, wetlands, riverbank gardens and NTFPs, as well as rice production. On the Thai side of the river livelihoods are mixed but mainly dependent upon agriculture although fisheries is an important livelihood source in some areas such as the Songkhram basin. Relatively high poverty levels in Lao PDR mean that the population there is potentially vulnerable to the impact of mainstream dams. Lower poverty levels on the Thai side of the river mean that populations there are much less vulnerable to these impacts.
Zone 4 running from Pakse to Kratie has the lowest average population density of all the zones. Mainstream dam construction in this area will mean the inundation of around 143Km or 45% of the stretch. The population which will need to be resettled in this zone is estimated to be at least35 around 30,000 and directly affected populations are expected to be around 28,000. Populations in both the Lao and Cambodian stretches of zone 4 depend on fisheries and other river resources as an important part of their livelihood strategies. In the Lao areas populations are likely to be vulnerable as poverty rates are around 30‐40% and populations depend heavily on river resources, meaning they are likely to be adversely affected by changes due to mainstream dam construction. Stung Treng in Cambodia has a poverty rate of less than 20% but that in Kratie is around 30‐40%. Again high poverty rates and dependency of the population on aquatic resources suggest that these populations will suffer disproportionately from the any adverse ecosystem impacts resulting from the development of the mainstream hydropower dams.
Zone 5 running from Kratie to Phnom Penh and Tonle Sap has much higher populations living around the mainstream. This is a highly diverse area encompassing the large urban area of Phnom Penh and Tonle Sap. Fish consumption in this area is relatively high, with wealthier households tending to consume more fish. Whereas the poor rely on fish and other aquatic animals as a critical source of protein and nutrition. Around Tonle Sap in particular, rural communities are highly dependent upon aquatic resources. It is estimated that some communities living on floating villages are almost wholly dependent upon aquatic resources. The IBFM social assessment report (2007) suggests that overall dependence on fisheries and other aquatic resources is high in rural areas but relatively lower in urban areas. Poverty rates vary widely between 20% in urban areas to 50‐60% in outlying rural areas. The combination of poverty and fisheries dependence in rural communities in the zone suggests that any change in fisheries productivity will have a significant impact on these populations. Estimates suggest that up to 1 million people in this zone would be seriously affected by any reduction in fisheries resulting from the construction of mainstream dams.
34 At least, as no figures for Lat Sua hydropower project were available at the time of writing. 35 Figures for resettlement and affected population were not available for the Thakho project, these estimates only include Stung Treng and Sambor.
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Zone 6 running from Phnom Penh to the sea is the most densely populated stretch of the river consisting largely of the irrigated rice paddies of the Mekong delta. The area is highly dependent upon the Mekong river for irrigation and nutrient replenishment during floods. Fisheries and shrimp production are also important. While employment in agriculture and fisheries is low compared to other areas in the basin, many of the industries which employ the population are directly dependent upon the natural resources of the delta (e.g. food and beverage manufacture). Higher income levels in the delta and a lower level of dependency on the aquatic resources likely to be affected by the mainstream dams means that impacts of the dams are likely to be less acute in the delta. However, even with relatively low poverty rates high population densities mean that the absolute number of poor is higher than in
5.4.4 DISTRIBUTION OF IMPACTS BY COUNTRY
Cambodia: Key beneficial impacts of mainstream hydropower development in Cambodia are likely to include increased foreign exchange earnings from power exports, increased direct investment in the hydropower facilities themselves (some portion of which is likely to enter into the domestic economy), increased government revenues (generated from taxation, licensing and equity shares in the projects), improved power supply and reduced power price (particularly important in the Cambodian context where power costs represent a key constraint on industry) and the generation of the employment opportunities in the construction, operations and maintenance of the hydropower facilities.
Key negative economic impacts that Cambodia is likely to experience if these projects are developed are a highly significant reduction in capture fisheries which will have a significant macro‐economic impact (given the importance of the Mekong fisheries to the Cambodian economy) and perhaps more significantly an adverse poverty reduction impact especially in vulnerable populations in zones 4 and 5 (see above). In the case of the projects sited in Cambodia direct impacts due to loss of land, assets and other livelihoods are likely to be important. It is important to bear in mind that even if the Cambodian projects did not go ahead fisheries in Cambodia would be adversely affected by projects in Lao PDR/Thailand albeit to a lesser extent (see fisheries paper). The impact on food security and economic costs associated with increased malnutrition amongst vulnerable populations are likely to be high. Better analysis of these indirect costs needs to be conducted to allow a proper assessment of the costs of these developments.
In short, Cambodia is likely to bear the brunt of the decline in fisheries due to the importance of this sector and the dependence of large sections of the population on fisheries for their livelihoods and as a key source of nutrition. Domestic hydropower projects will bring benefits but is not clear whether the financial and economic gain these may imply will offset the largely hidden costs borne by fisheries dependant populations. More research is needed to establish the likely magnitude of these costs.
Lao PDR: Beneficial impact of mainstream hydropower development for Lao PDR, given that it will play host all or in part to 10 of the 12 proposed projects, include ‐ as with Cambodia ‐ increased foreign exchange earnings from power exports, increased direct investment in the hydropower facilities themselves (some portion of which is likely to enter into the domestic economy), increased government revenues (generated from taxation, licensing and equity shares in the projects) and the generation of the employment opportunities in the construction, operations and maintenance of the hydropower facilities. Domestic power supply is expected to be less of a benefit to a country which has as yet a very small manufacturing sector. However, there is the possibility that these hydropower projects may facilitate the development of mining projects in some locations.
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Many important negative impacts in Lao PDER relate to the changing hydrology of the areas within which the dams maybe constructed. Loss of production land, housing, other productive facilities, infrastructure and amenities are all likely to be significant in both upstream and downstream areas. In particular loss of river bank gardens and negative impacts on in‐stream infrastructure due to changing water levels and increased erosion will be costs that are likely to be borne by local populations and local governments respectively. Loss of aquatic resources is likely to be significant for populations along the river, this impact is likely to be less wide spread than in Cambodia. Nevertheless, loss of aquatic flora and fauna, and fisheries productivity is likely to have highly significant if localized poverty and nutritional implications similar to those outlined for Cambodia. Indirect impacts though exchange rate appreciation may have negative implications for some sectors such as manufacturing and agriculture – although this will depend upon the macro‐economic management policies and capacities of the government.
A key question for Lao PDR emerging from the discussion of both macro‐economic and poverty impacts are the extent to which the government will be able to use net revenues from hydropower to address the uncompensated impacts of these developments. And related to this, more broadly, the extent to which the government is able to manage these revenues in such a way that they improve productive capacity and competitiveness in sectors which are important for poverty reduction (i.e. manufacturing and agricultural sectors).
Thailand: Key benefits for Thailand while sizable in terms of these projects are not particularly significant in terms of the overall Thai economy. While there are undoubtedly economic benefits from a cheaper and more stable electricity price from these projects given the size of Thai power demand it has quite a small impact. Thai project developers will also reap benefits as will their suppliers (mainly construction firms, engineering firms and their employees), increased profits for these companies will also lead to greater tax returns. However, when considered against the size and diversity of the Thai economy these impacts do not seem particularly significant.
Negative impacts are much more localized. As with Lao PDR and Cambodia key economic costs will be borne by river dependant populations especially fisher folk and those engaged in varied subsistence livelihood strategies. The north east of Thailand is the poorest in the country, however compared to the other LMB countries the population in the Thai portion of the basin is comparatively well off. This population also has greater opportunities to diversify livelihoods way from dependency on the river resource base. Therefore, while the initial impact on the river basin population is likely to be significant, this population is likely to be able to adapt to this impact more effectively that affected communities in the other riparian countries.
Vietnam: Key benefits for Vietnam are likely to be similar to those for Thailand, although the benefits of the project developments are likely to be somewhat less as fewer project inputs are likely to come from Vietnam. On the other hand, the benefits of the additional power supply are likely to be more significant ‐ reflecting supply shortfalls and the overall size of Vietnamese power demand. However, it is difficult to argue that these beneficial impacts are particularly significant in the context of a Vietnamese economy that would be likely to continue its break‐neck growth with or without these projects.
Hydropower development in general, however, is likely to be highly significant for the Mekong delta as changes in seasonal flow rates, sedimentation and river ecosystems have wide spread effects. While it has been noted that the mainstream dams may have some limited effects in lessening flood‐peaks and trapping some sediment, these are not likely to be significant for the delta beside the impact of the
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Chinese mainstream and tributary projects. The impact on fisheries is likely to be the key negative impact experienced by river dependent communities in Vietnam. As elsewhere in the basin capture fisheries are an important livelihood component. The significant loss of fisheries in the basin will therefore have serious implications for fisheries dependent livelihoods and nutrition in the Mekong delta. As in other areas the poor are likely to be most severely affected by these fisheries impacts as unlike land or other privately owned assets these represent a commons accessible to the poor.
5.4.5 CONCLUSION
The distributional analysis shows that different groups, zone and countries are likely to experience very different streams of costs and benefits resulting from the impacts of the proposed mainstream hydropower dams. Rural populations, river dependant populations and the poor stand to lose most. In fact impacts are concentrated on some of the most vulnerable populations. Whereas the main the benefits will accrue to developers and their investors, to a lesser extent power consumers and host governments. These beneficiaries notably exclude the rural poor who are often not connected electricity grids. The distributional implications of these developments should be more fully considered.
It is also worth nothing that to some extent the economic cost‐benefit case for these developments may be beside the point for the host countries. This is because most of these benefits accrue to the power consumers and perhaps the developers. While developers may need to compensate for direct costs, it is unclear where the burden of the indirect costs will fall (such as poverty impacts, the impacts of changing hydrology and geomorphology on in stream infrastructure etc). If it falls to the host governments to address these indirect impacts using state budgets, from the perspective of the host country, the calculation is not of the economic benefit of the power –which is capture by foreign consumers –but the uncompensated costs of the projects considered against the increase in budget revenues generated by the project.
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6 HYDROLOGY & SEDIMENT
6.1 STRATEGIC ISSUES
• Stream power and energy transport in the Mekong
• Water surface level changes
• Coarse sized sediment fate and transport
• Fine sized sediment fate and transport
6.2 DATA SOURCES AND POTENTIAL UNCERTAINTIES
The flow and water level figures quoted in the SEA (across all themes) are based on the model simulations undertaken as part of the BDP, with limited data available from Zone 1 (Yunnan province). Recent interactions with the Chinese authorities (ESCIR) indicate that there are some discrepancies between the predicted seasonal changes caused by the Yunnan cascade as modeled by the BDP and ESCIR (Table 6.11). The regulated hydrological regime will depend heavily on the reservoir operating strategy at each of the 8 dams in the Yunnan cascade and of the cascade as a whole. Therefore, there may be some adjustment to the predicted values for flow and water level, though the substantive conclusions are expected to hold.
The SEA team has adopted the BDP modelling results for two reasons: (i) the predicted reduction of wet season flows (700cumecs) represents ~90% of the total active storage of the Yunnan cascade and so is considered suitable for the purposes of the SEA, (ii) to stream‐line the SEA with the BDP scenarios and thereby increase the utility of the SEA.
Table 6.1: Changes to seasonal flows based on the MRC and ESCIR modelling
Seasonal flow MRC ESCIR
3 Increase flow in dry season (m /s) 690 1,200
3 Decrease flow in wet season (m /s) 700 1,400
Sediment records have been collected from the Mekong River since the 1960s using two methods: (i) Suspended Solid Concentrations (SSC) – collected since the 1960s, and (ii) Total Suspended Solids (TSS) – collected since the 1980s. However, between sample sites and over the past 40‐50 years the field and laboratory methods employed and the frequency of sampling has been somewhat erratic. This has resulted in a large level of uncertainty and divergence in estimates of the Mekong sediment load. The
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MRC IKMP has initiated a program to consolidate the sediment database and ensure ongoing sampling becomes more consistent, however, for the SEA there remains some divergence in expert opinion on: (i) the total Mekong sediment load, (ii) the source of sediments, (iii) the grain size distribution of the sediment profile, and (iv) the proportion of bed load in the sediment regime. The SEA has provided estimates on these important questions supported by appropriate references, and has also indicated the range of opinion for certain key estimates to indicate the scale of divergence.
6.3 SUMMARY OF PAST AND FUTURE TRENDS WITHOUT LMB MAINSTREAM HYDROPOWER
6.3.1 STREAM POWER
Stream power (measured in units of MW/km or kW/m2) is the rate at which energy is lost in moving over the bed of the river, and lost to turbulent flow dissipation. It links key hydraulic features of the Mekong system, including: power production, energy dissipation, geomorphology, flow turbulence and sediment transport. The length wise power dissipation along the Mekong River in Zone 2 and 3 ranges between 5 to 30 MW per km distance, depending on flow rate m3/s and average channel gradient. The stream power per unit area is this value divided by the width of the streambed, so that the narrower the reach the larger is the unit area stream power. Figure 6.1 plots the unit length power dissipation for the Mekong River under natural flow conditions demonstrating that there is an increase in dissipation from Zone 2 to Zone 3 and then a sharp decline as the river enters the floodplains of Cambodia. The vast majority (in the order of 96%) of stream power is applied at the bed and banks of river channels.36 Consequently, stream power is sufficiently large in localized river reaches that a substantial part of the bed load is thrown into suspension for short distances.
Figure 6.1: Natural rate of energy dissipation of the Mekong River (MW/km)
35.00
30.00
25.00 MW/km 20.00
15.00 dissipation
Power 10.00
5.00
0.00 2,300 2,500 2,700 2,900 3,100 3,300 3,500 3,700 3,900 4,100 Distance from source (km) Sua
Lay Koum
Treng
Chom
Sahong Lat Sambor
Pak Prabang Ban
Xayaburi Pak Beng Pak Xanakham Don Stung
Luang Existing power dissipation rate
36 Annandale, G.W. 1987. Reservoir Sedimentation, Developments in Water Science No. 29. Elsevier Science Publishers B.V, Amsterdam The Netherlands
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Stream power is important to almost all aspects of the river, including movement of coarse and fine sized sediment, the development of deep holes in the bedrock, channel geomorphology, bank erosion, and formation of mid‐channel islands. Stream power is proportional to the water surface slope and the in‐ channel flow and is largest during the peak flood season, at maximum hydrograph levels.
Figure 6.2: Natural and human induced energy dissipation on the Mekong River: (left) Water power is being rapidly dissipated as the mainstream river flows over a bedrock outcrop, upstream of Luang Prabang, (right) Energy dissipation immediately downstream of a major irrigation intake, downstream of Phnom Penh. The water surface drops about 0.5 m because of power dissipation as the flow enters the canal.
The 20 year scenario trend is for the peak stream power to shift downwards, associated with smoothing of the annual hydrograph because of regulation by proposed dams/reservoirs with large storage (figure 3). Table 6.2 outlines the predicted reduction in maximum daily flows for the 5 zones of the LMB. The largest reduction in maxima will occur in the upper reaches of the LMB (10‐20% in Zone 2) with the change reducing in significance further downstream (5‐10% in Zone 3, 4, 5 and ~5% in Zone 6). Further, the majority of the reduction occurs under the BDP Definite Future scenario suggesting that the driver of the trend is regulation of mainstream flows in Zone 1 by the Yunnan cascade of 8 hydropower projects.
Table 6.2: Changes to the Averaged maximum daily flow on the Mekong mainstream.
BDP Scenario Chiang Saen Vientiane Pakse Kratie Tan Chau Chau Doc Baseline (BS) 6,476 12,121 27,333 36,297 20,764 5,605 Definite Future (DF) 5,512 10,848 25,919 34,793 20,336 5,406 20Y without LMB mainstream (20Yw/o) 5,403 10,705 25,655 33,909 19,885 5,256 % change DF from BS 15% 11% 5% 4% 2% 4% % change 20Y w/o from BS 17% 12% 6% 7% 4% 6%
Peak stream power is the main factor influencing the transport of coarse sediment, and erosion/deposition processes along the river channel. In Zone 2, the peak stream power in the 20 year scenario will decrease by about 10 % to 20% in an average flood year, associated with the projected reduction of the hydrograph peak. Climate change, with anticipated effects on future flood runoff from intense heavy rain systems, may offset or counteract this decline, but the relative magnitudes of the super‐imposed changes on the hydrograph cannot be quantified in this study.
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6.3.2 WATER SURFACE LEVEL CHANGES
Water surface levels in the Mekong mainstream fluctuate relatively slowly, because of the large size of the river. Rates of change of water surface elevation are highest with the arrival of the flood pulse, and are typically up to about +/‐ 0.16m/day at Luang Prabang, +/‐ 0.11m/day at Pakse and about 0.09m/day at Stung Treng. Extremities of water surface levels are experienced seasonally, and follow a pattern that is determined by the reach of the river, and the maximum/minimum flow for the season. The relationship between the water surface level and the flow magnitude is described by the rating curve, and each river reach has its own individual rating curve. The largest recorded water surface levels are from years with the largest recorded flood events, for the mainstream river.
Fig 6.3: Changes to the Averaged annual hydrograph for Chiang Saen (left) and Pakse (right). The effects of upstream regulation can be clearly observed in the reduction of the hydrograph peak and an increase in the dry season flow. Comparison of the Definite Future and 20Y scenarios for Chiang Saen indicates that the majority of this change is induced by the development of the Yunnan cascade.
7,000 30,000
6,000 25,000
5,000 20,000
4,000 15,000 3,000 10,000 2,000 5,000 1,000
0 0 1‐Jan 1‐Feb 1‐Mar 1‐Apr 1‐May 1‐Jun 1‐Jul 1‐Aug 1‐Sep 1‐Oct 1‐Nov 1‐Dec
Q Baseline (m3/s) Q Definite Future (m3/s) 20Y (m3/s) Q Baseline (m3/s) Q Definite Future (m3/s)
Fig 6.4: Water level fluctuations along the Mekong River: (left) Irrigation intake upstream of Luang Prabang. The maximum height of the structure is set to be higher than the highest floods, and the bottom of the tower is set on bedrock, at a location that does not accumulate sand. Seasonal water level fluctuations in Zone 2 are typically 5‐8m; (right) Government water level gauge at Kratie. The slope gauge is set at an angle, built in to the side of the concrete steps. Seasonal water level fluctuations for the Mekong mainstream are 15 to 20 m at this location
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River bank inhabitants, such as fisherman living in floating homes, are used to river levels that fluctuate slowly, and there is typically many days of time to anticipate the onset of floods.
FLOOD EXTENT
There are two components to the Mekong floodplain: (i) the vast expanse of floodplain downstream of Kratie including the Tonle Sap system and the Mekong Delta, (ii) the smaller floodplains alongside the Mekong channel in Zone 2, 3 and 4, typically located at tributary confluences and reaches of flatter topography. 83% of the Mekong flooded area is located in Cambodia and Vietnam, these areas are important for regional biodiversity, as well as national agriculture and fisheries production. The majority of Cambodian flooded areas reach depths of more than 3m during the flood season, while Vietnamese areas reach depths of 0.5 – 3.0m. Approximately 750,000ha lie along the Mekong channel in Lao and Thailand, of which 64 – 69% flood to depths great than 3.0m.
The Definite Future will see a typical reduction of ~250,000ha in flooded area, the majority of which will affect areas with flood depths greater than 3m. This will affect more than 15% of the flooded areas in Thailand and Lao, and less than 5% of the area in Cambodia and Vietnam. The Definite future represents the dominant change to the flood regime, with only marginal additional effects under the 20Y scenario (see Fig 6.5).
FLOOD TIMING AND DURATION
The LMB experiences four identifiable seasons which occur with regularity: (i) The low flow season begins at the end of the calendar year and extends through to mid/late May. Flow is maintained by snow melt in the Mekong headwaters and the minimal natural storage of the basin in the soil horizon, groundwater and wetlands; (ii) The transition to flood season is characterized by the first spates of the Monsoon season with an increase in both flow rate and flow variability. The transition season ends in mid July; (iii) The flood season begins when flows exceed the long term average and is characterized by the flood peak in September and sometimes a smaller leading peak. The season finishes in early to mid‐November when flow drops below the long term annual average; and (iv) the transition to dry season as flood waters and surface water storage in the basin drains back to the mainstream.
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Fig 6.5: Example of change in flooded area for different BDP scenarios (source: Piman, 2010)
Flooded area assessments '000 ha 5,000 Baseline Lao Thailand Cambodia Vietnam Total Total flooded area by depth class Less than 0.5 m 18 17 142 307 484 4,500 0.5-1.0 m 25 24 228 668 945 1.0-3.0 m 82 89 708 794 1,673 More than 3.0 m 270 232 1,055 5 1,562 4,000 Totals 395 363 2,133 1,773 4,664 3,500 Definite Future Scenario Lao Thailand Cambodia Vietnam Total Less than 0.5 m 17 18 175 374 584 3,000 0.5-1.0 m 20 22 205 712 959 1.0-3.0 m 72 79 673 666 1,490 2,500 More than 3.0 m 224 177 977 3 1,380 Totals 332 296 2,029 1,756 4,413 2,000 Less than Reductions from baseline 16% 18% 5% 1% 5% 0.5 m
1,500 0.5-1.0 m 20-year Foreseeable Future Lao Thailand Cambodia Vietnam Total Less than 0.5 m 18 19 177 395 609 0.5-1.0 m 18 21 208 717 963 1,000 1.0-3.0 m 1.0-3.0 m 69 77 664 634 1,444 500 More than 3.0 m 223 170 943 3 1,339 More than Totals 329 287 1,991 1,748 4,355 3.0 m Reductions from baseline 17% 21% 7% 1% 7% 0 Change from Definite Future -1% -3% -2% 0% -1% BS DF 20-yr
Table 6.3: Changes to the timing and duration of the Mekong Hydro‐biological seasons: the Mekong hydrological regime is characterised by four distinct seasons, changes induced predominantly by hydropower development will see a major disruption in the timing and duration of these seasons with a reduction in the duration of the flood season and the complete disruption of the transition season which is important in triggering a wide range of ecosystem functions all the Mekong mainstream and its floodplains.
STATISTICAL END OF END END OF PARAMETER DRY TRANS. A FLOOD DURATION DRY + STATI 2*Q(min) 2*Q(min TRA FLO TRA ON SCENARIO Q(ave) m3/s m3/s ) Q>Q(ave) Q 78 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | HYDROLOGY & SEDIMENT 20Y w/o Same as 20Y BS 4,300 2,024 14‐May 25‐Jun 14‐Nov 42 142 181 DF 4,282 3,572 10‐Jun 27‐Jun 13‐Nov 17 139 209 VTE 20Y 4,368 4,310 5‐Jul 6‐Jul 13‐Nov 1 130 234 20Y w/o 4,368 4,089 26‐Jun 1‐Jul 13‐Nov 5 135 225 BS 9,390 3,065 18‐May 16‐Jun 8‐Nov 29 145 191 DF 9,319 4,813 29‐May 14‐Jun 7‐Nov 15 146 204 PK 20Y 9,043 5,551 1‐Jun 22‐Jun 6‐Nov 21 137 207 20Y w/o 9,043 5,286 1‐Jun 20‐Jun 6‐Nov 19 139 207 BS 12,869 4,003 17‐May 17‐Jun 12‐Nov 31 148 186 DF 12,798 5,907 23‐May 17‐Jun 11‐Nov 25 147 193 KT 20Y 12,423 6,899 1‐Jun 25‐Jun 10‐Nov 24 138 203 20Y w/o 12,424 6,660 31‐May 19‐Jun 10‐Nov 19 144 202 BS 10,488 4,321 25‐May 30‐Jun 17‐Dec 36 170 159 DF 10,633 5,945 4‐Jun 2‐Jul 18‐Dec 27 169 169 TC 20Y 10,421 3,222 13‐Jun 9‐Jul 16‐Dec 26 160 179 20Y w/o 10,405 6,609 10‐Jun 5‐Jul 17‐Dec 25 165 175 BS 2,121 277 ‐ 15‐Jul 11‐Dec ‐ 149 ‐ DF 2,126 496 ‐ 16‐Jul 11‐Dec ‐ 148 ‐ CD 20Y 20Y w/o Was not calculated The trends expected to 2015 are: • Onset : changes to the timing of the seasons is greatest in the upper reaches of the LMB where the Lancang flows contribute a greater proportion. The timing of Transition A from the dry to the flood season will be most affected, starting ~7‐ 8weeks earlier at Chiang Saen and ~1 week at Kratie. This season is important in triggering seasonal patterns in the river’s ecology (for example fish migrations). Upstream of Vientiane will also see an earlier onset of the flood season, though tributary flows from the left bank will reduce this to negligible variation downstream of Vientiane. • Duration: Upstream of Pakse will experience a 2‐4week reduction in the transition season from Dry to Flood, which will drop to ~1 week in the Mekong floodplain. The duration of the flood season is not expected to be significantly affected except at the uppermost reaches of the LMB where the UMB flows still dominate wet season volumes. These cumulative reductions will see an increase in the duration of the combined Transition + dry season. • Magnitude: dry seasonal flows will increase by 70% at upstream stations decreasing to a 10% at the Mekong Delta. Conversely, wet season flows will decrease by up to 18% at upstream stations decreasing to 2% change at the Mekong Delta. • Cumulative: The cumulative effects of the changes to the hydro‐biological seasons is a reduction in duration of the two transitions seasons combined with a reduced variability between the wet and dry seasons. These two factors serve to homogenize the Mekong hydrograph and subdue the prevalence of the flood pulse. This is most pronounced in the upper reaches of the LMB reducing downstream as the left bank tributaries begin to influence the hydrograph. The trends to 2030 will see an extension of the above. The major impact from the combined effect of the Yunnan cascade and the tributary developments will be the loss of the transition seasons and resulting 79 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | HYDROLOGY & SEDIMENT from a more even hydrograph. The spates and first flushes of the transition to flood play an important part in triggering key ecosystem functions of the Mekong system including spawning and migration of aquatic biota as discussed in the aquatic and fisheries themes. TONLE SAP The natural cycle of water surface fluctuations in the Mekong mainstream drives the flow in and out of the Tonle Sap system contributing ~57% of the inflow to the lake, and determines the extremities of water surface levels in Tonle Sap Lake which experiences average seasonal WL changes of 8m. Typically the area of the lake fluctuates between 2,200km2 and 13,200km2 between the wet and dry seasons (table 2). Table 6.4: interannual variation in the hydro‐physical dimensions of the Tonle Sap Lake (MRC, 2006) TIME SERIES WL [m] SA [km2] V [km3] 1997‐2003 max min diff max min diff max min diff Max 10.36 1.48 8.88 15,278 2,402 12,876 76.05 1.83 74.22 Min 6.86 1.19 5.67 9,637 2,061 7,576 33 1.35 31.65 Average 9.11 1.34 7.77 13,218 2,237 10,981 59.56 1.59 57.97 The present trend (with 20 year scenario) is for a reduction in the hydrograph maxima, and an increase in the hydrograph minima, associated with water storage in large capacity reservoirs. This will reduce the hydraulic gradient driving flow in and out of the Tonle Sap system and consequently increase the dry season inundated area while also reducing the wet season inundated area of the lake. By 2015, upstream regulation will seasonally alter water levels in the Tonle Sap Lake by +0.1m/‐0.3m, which will decrease the maximum extent of flooding in the Lake by 3‐5%, and increase dry season lake area by 5‐8%. The decrease in wet season lake area will reduce the area of fringing forest flooded and reduce the littoral zone of the lake both of which are critical aspects of the lake’s high productivity. The increase in dry season lake area will further exacerbate the reduction in the Tonle Sap floodplain by permanently inundating some areas. Together these effects will induce a 500‐600km2 reduction in floodplain subject to the seasonal flood pulse and oscillation between terrestrial and aquatic environments – which represents 5‐10% reduction in the floodplain area. This will reduce the productivity of the Tonle Sap System, but further study is required to quantify the magnitude of this reduction. Under the 2030 scenario these changes to the Tonle Sap system will undergo even more extreme change with an expected 900km2 reduction in the Tonle Sap flood plain area. Fig 6.6: Changes to the average monthly area of the Tonle Sap lake under: (i) baseline, (ii) definite future, and (iii) 20Y BDP scenarios. 80 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | HYDROLOGY & SEDIMENT HOURLY AND RAPID FLUCTUATIONS IN WATER LEVELS The river does not display signs of daily or hourly rapid fluctuations in the LMB at present. Under the 20 year scenario these changes may or may not be present, and will depend on how the tributary power dams are operated, and the effectiveness of a proposed re‐regulating structure downstream of the China dams. 6.3.3 FATE AND TRANSPORT OF COARSE SIZED SEDIMENT Coarse sized sediment e.g. coarse sand, gravel and larger sizes, is conveyed in the Mekong River mainstream as bed load, and moves downstream annually by distances of a few tens of meters to a few kilometers. Prior to the closure of Manwan dam (1992), there were no anthropogenic and only minor natural obstacles (e.g. deep pools) to the transport of bed load in the mainstream. Figure 6.7: Action of water on particles near the stream bed, rolling and saltating grains from Dunne and Leopold37 1978. Stream power is fed from the moving water to the bed, and supplies energy to move coarse particles in a serious of jumps and temporary suspension. 37 Dunne T., and L.B. Leopold 1978. Sediment production and transport. Chapter 17 of Water in Environmental Planning. W.H. Freeman and Company. 818 pp. 81 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | HYDROLOGY & SEDIMENT No measurements have been made of bed load transport in the Mekong, and the best information is from calculations that have been found to apply in other river systems, based on the suspended load transport. Fig 6.8: Coarse sand deposits in Zone 2: (left) Pakbeng: coarse sand, resupplied and moved downstream during peak floods. Diminishing amounts are predicted, because of trapping by existing and proposed dams in China, and; (right) Nam Ou: coarse and medium sand, resupplied and moved to the mainstream during peak floods. Diminishing supplies are predicted, because of trapping by the (10) proposed 20 year scenario dams. Present trends are for a reduction in the transport of coarse sized sediment in the river downstream of the China border, as the effects are felt of the blockage of transport caused by Manwan, Jinghong and Mengsong dams. With the future completion of an additional two dams in China downstream of Jinghong, the amount of river bed able to resupply coarse sediment will be reduced. For the downstream river, reductions in the transport of medium/coarse sand and finer sizes are felt first, as this is rapidly depleted from storage on the bed and banks of the river. The sedimentary nature of the river bed coarsens in response. This effect is much larger than impacts that will be caused by climate change over the 20 year scenario. DEEP POOLS There are at least 335 deep pools along the thalweg of the Mekong mainstream. These pools are dynamic features of the river channel consolidating sediment movement into a pulse‐like wave which transports sediment between adjacent zones of sediment storage over the monsoon flood cycle. The deep pools play an important role in regulating the downstream progression of sediment and building in‐channel features such as islands and sand bars, which are important for the river’s biodiversity. No information is available on the past trends in either the location or number of deep pools. By 2030 both the peak flows and sediment load will be reduced, however the reduction in peak flow is not expected to reduce the in‐pool velocity enough to prevent entrainment. At Chiang Saen the duration of the flood season will be shortened by ~4weeks (25% of historic flood duration), this will affect the time over which scour velocities are reached resulting in only partial scouring of the deeper pools and increasing the time‐step over which the sediment wave completely passes through the pool. The reduction in sediment load because of the reservoirs in the Definite Future is not likely to induce any immediate changes in the functioning of the deep pool as their buffering effect on sediment movement has resulted in a significant volume of sediment stored within the channel banks. Therefore, in the short 82 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | HYDROLOGY & SEDIMENT term the pools will continue to function naturally (with a potential reduced scouring efficiency) as ‘crossings’ continue to migrate downstream. In the long term, upstream crossings will disappear as they translate downstream and are not replaced, such that the deep pools eventually become static ‘holes’ and no longer dynamic components in the translation and storage of sediment and bed load. 6.3.4 FATE AND TRANSPORT OF FINE SIZED SEDIMENT Fine particles (sometimes known as wash load) move in river systems in proportion to their availability in the river basin and its tributaries from erosion processes, and these particles frequently constitute the largest part of the sediment transport. In rivers that have no dams, there is no hydraulically imposed limit to the transport of these fine materials. They pass down the river system easily and rapidly, and may go all the way to the delta in a single flood season. If significant amounts of the wash load are removed from the system by anthropogenic changes, it is almost impossible for the river to resupply the wash load to meet its previous natural magnitude. Fig 6.9: fate and transport of fines in the Mekong River: (left) Fine particles moving in suspension in the Mekong mainstream (nearfield), contrasted with relative absence of fine particles in flow entering from Nam Ou (farfield), low flow season, January 2008. Flow from left to right; (right) flood flow season: Fine particles moving in suspension across the Cambodian floodplain during a high water event, September 2002. Flow away from bridge (upwards and to left in photo). The load of suspended (fine sized) particles has been measured at a number of stations on the Mekong mainstream since year the 1960s using two different methods (TSS and SSC). At Kratie the sediment load is estimated at 165million tonnes/yr with 145million tonnes from upstream areas and ~20million tonnes from the 3S sub‐basin (MRC, 2010). There is considerable divergence in opinion surrounding these estimates (c.f. the SEA Hydrology and Sediment baseline working paper), with estimates ranging between 140‐190million tonnes/year at Kratie and the contribution from the 3S river basins ranging between 10‐ 52%. This is reflective of inconsistencies in the sediment database as mentioned earlier. Higher estimates of the 3S contribution are based on marine sedimentary profiles taken from off‐shore core samples, these estimates give a good indication of the sediment provenance over millennia and even thousands of years, 83 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | HYDROLOGY & SEDIMENT however it is difficult to detect nuance in the sediment dynamics which may be occurring at hundred year or shorter times scales from these cores. No detailed sediment monitoring data was available further downstream than Kratie, however best estimates suggest that 75‐85% of the Kratie Load enters the Mekong Delta (120‐140 million tonnes/yr) (Kummu et al, 2008). Preliminary assessment of the water slope of the Mekong Channel between Chau Doc and Can Tho during the 2000 flood suggests that in this reach the load is primarily fine sand, silt and clay sized material because of the low energy nature of the river. The order of magnitude reduction in sediment supply expected at the Delta is approximately 20% (MNRC, 2010). Any resupply of sediment to Mekong flows from storage in the channel and banks (typically fine sands and larger) is not likely to offset the reduction at the delta because under baseline conditions there is not expected to be sufficient energy to entrain these larger size particles past the Cambodian floodplain. This compares with a total sediment load in river of similar size (Mississippi River38) of about 400 million tonnes about a century ago (prior to development). The suspended load transport of the Mississippi at the delta during the last 2 decades has been 36% of this value, associated with past construction of dams and bank stabilization structures. A significant proportion of the Mekong suspended load is removed naturally from the river upstream of the delta, in the Tonle Sap system, and in the Cambodian and Vietnamese floodplains. Maximum transport of fine particle load is in the reach downstream of Stung Treng, to about Kampong Cham. The present trend is for significant reductions in the transport of fine material, because of the operation of reservoirs with large storage, in China, and on major tributaries. Estimates based on trapping efficiency of the present and 20 year scenario reservoirs are that 80% of the sediment load of the river will be removed. Figure 6.10: Indicative changes to the sediment load composition for Kratie & Tan Chan: (left) Kratie: under the past and future without the mainstream dams sediments up to coarse sized sand are expected to be transported downstream, which is confirmed by the presence of the large sand and gravel extraction industries downstream of Kratie; (right) Tan Chau/Chau Doc: few medium and larger sized sediment is expected to be transported through the Cambodian flood plain such that the majority of the sediment currently entering the Mekong Delta are clay’s and fine‐sized sand. 38 Meade, R.H., and J.A. Moody 2009. Causes for the decline of suspended sediment discharge in the Mississippi River system, 1940 ‐2007. Hydrology Processes, vol 24, pp 35‐49. 84 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | HYDROLOGY & SEDIMENT 6.4 EXPECTED DIRECT EFFECTS OF THE PROPOSED LMB MAINSTREAM PROJECTS 6.4.1 STREAM POWER The operation of the proposed mainstream reservoirs will cause a major and irreversible shift in the way stream power is dissipated in the river. The present and Definite Future stream power that is naturally dissipated in the river, order of about 5 to 20 MW per kilometer distance, will be reduced to about zero MW per km during low and medium flows in the reaches that include the reservoirs upstream of the dams. At high flows the power dissipation in the reservoirs will be above zero, but will not be distributed in the same way as the present and future trend situation. The length of river affected constitutes about 66 % of the total 1760 km river distance, from the proposed Sambor dam site to the top end of the reservoir behind the proposed Pak Beng dam site, see profile Figure (11). The river will be transformed from a live river for the majority of the distance, to a series of impoundments with slow water movement, held back by the cascade of dams. The only substantial parts that will remain live river reaches are from below the proposed Pakchom dam site downstream to 80 km southeast of Savannakhet, from below the proposed Ban Koum dam site to the upper end of the reservoir behind the proposed Stung Treng dam, and downstream of Sambor. At the proposed dams, the stream power will be released at the turbines, in the tailraces, and (during spillage events) at the dam spillways. These engineered water power releases will be localized and concentrated, and will have no resemblance to the present and future trend of the Mekong river water flow. With a typical reservoir length of about 100 km, the accumulated power will amount to 500 to 2000 MW at each of the dams, and, with the present proposed sizing of the turbines, it will be possible to capture a substantial part of this stream power for conversion to electrical energy, if construction proceeds. The production and sale of electricity is the major opportunity that arises from the proposed projects, and is the reason why there is interest on the part of developers in proceeding. The change in the way stream power is distributed will have links with other natural processes, such as: 85 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | HYDROLOGY & SEDIMENT • Major changes to sediment transport of all sizes (see Theme Sediment Transport) • Functioning of deep pools • Major changes in transport of organic and woody debris • Significant and irreversible changes in fisheries migration and passage • Additionally, stream power changes will have links with risk factors for anthropogenic uses of the river, such as detriments to navigation and detriments to fishing opportunities. 86 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | HYDROLOGY & SEDIMENT Fig 6.11: Longitudinal profile of the Mekong River with LMB mainstream projects (to be inserted) 87 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | HYDROLOGY & SEDIMENT Fig 6.12: Changes to stream power of Zone 2 and 3: the development of hydropower on the Mekong mainstream will concentrate energy dissipation at the dam sites as the projects generate electricity. This will result in a decrease in energy dissipated along the channel bed of the reservoirs and reaches sufficiently far downstream of the dam wall. 35.00 30.00 25.00 MW/km 20.00 dissipation 15.00 Power 10.00 5.00 0.00 2,300 2,500 2,700 2,900 3,100 3,300 3,500 3,700 3,900 4,100 Distance from source (km) Lay Sua Chom Koum Treng Pak Lat Sahong Prabang Xayaburi Sambor Pak Beng Xanakham Pak Ban Don Stung Luang Existing power dissipation rate Future power dissipation rate with LMB mainstream projects 6.4.2 WATER SURFACE LEVEL CHANGES For 7 of the proposed projects, the dams will be sufficiently high that water levels in the reservoirs behind the dams will be above the highest ever recorded river elevations for significant distances upstream. For example at the Luang Prabang dam, the reservoir behind the dam will be at about 310 m elevation, and this is higher than the highest recorded flood level for a distance of many kilometers upstream of the dam. Areas that were previously floodplains areas will be drowned by the proposed reservoirs. More than 5‐10% of the river valley, in the total distance of 1760 km will be affected by receiving inundation at levels never experienced in the history of data collection for the river. 6.4.2.1.1 IRRIGATION Pump stations along the river may need rebuilding/relocating, to allow for operation at these new water levels. There are approximately 700 existing and proposed pump stations of various sizes drawing from the Mekong River (Figure 6.13). About half (309) of these pump stations will be affected by the mainstream reservoirs (Table 6.5). The total loss of bank side growing areas from permanent inundation from the reservoirs in this distance will be a certain risk. Partial losses of bank side growing areas will apply to approximately an additional several hundred km of the mainstream river, associated with high water levels (see terrestrial paper). Additional bank side growing areas that are present on tributary rivers, affected by Mekong river backwater inundation, will be at certain risk. 88 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | HYDROLOGY & SEDIMENT Table 6.5: Pump stations in the reservoirs and 100km downstream from the LMB projects UPSTREAM DOWNSTREAM No pump stations Total Area Irrigated No pump stations in Total Area Irrigated Proposed dam in reservoir (20Y scenario) 100km downstream (20Y scenario) (ha) (ha) Pak Beng 3 222 1 20 Luang Prabang 0 0 10 240 Xayaburi 10 264 1 40 Pak Lay 3 204 1 55 Xanakham 2 183 1 40 Pak Chom 1 40 45 13,928 Ban Koum 16 5,235 26 4,590 Latsua 1 32 157 6,115 Don Sahong 3 ‐ 0 0 Stung Treng 0 0 3 ‐ Sambor 6 17 19 719 TOTALS 45 6,197 264 25,747 Pump stations located in the reservoirs will need to be removed to higher locations remain operable; this represents a significant cost to the pump operators. The elevated water levels in the reservoir will reduce the pumping head of reservoir pumps such which will reduce the cost of pumping to irrigation schemes serviced by these pumps, though given the magnitude of change in water levels, it is likely that many of these pumps will need to be resized if the benefits of reduced pumping heads are not to be off‐set by reduced pumping efficiencies from wrongly sized machinery. The magnitude of this change for ‘reservoir pump systems’ will also depend on the drawdown in the mainstream projects. If they are used for peaking operation then a drawdown in the order of 1‐5m could increase the complexity of pumping operations and require changes to pump locations on a 12‐hourly time step. For projects downstream of the reservoirs the new flow regime imposed by the mainstream projects will induce migration of the river thalweg and would require many of these pump stations to be relocated. Further, water levels downstream of the dams are likely to continue to fluctuate at a seasonal scale, but could also fluctuate on a daily time‐step depending on project operating strategy. Figure 12 illustrates this situation for the Latsua project. 89 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | HYDROLOGY & SEDIMENT Fig 6.13: Location of the 712 existing and planned pump stations on the Mekong River in relation to the proposed LMB dams 90 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | HYDROLOGY & SEDIMENT Figure 6.14: Example irrigation pumphouses affected by LMB mainstream hydropower: (left) Ban Koum: 16 pumping projects are located in the reservoir which will require relocation as well as potential improvements to pumping heads; (right) Luang Prabang: 10 pumping projects are located downstream of the reservoir and will need rolocation and different operating strategies as the changed flow relocates the thalweg and induces variable flows potentially at a 12‐hourly time step. 91 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | HYDROLOGY & SEDIMENT RESERVOIR OPERATING STRATEGY Significant issues of rapid fluctuations of river flows and levels will arise from the proposed projects, because the time needed to open and close turbines is small, order of 10 minutes or less. Opening and closing turbines may arise from a variety of planned and unplanned circumstances, and breakdowns of plant and electrical transmission systems. For example, based on a peaking strategy of 12hours, fluctuations of 3‐5m could be expected at key towns downstream of the projects. Table 6.6 shows this for the case of Luang Prabang, Ban Koum and Stung Treng. The time elapse for a rapid fluctuation from opening the turbines at the proposed Luang Prabang dam site, for example, will be about 1 to 1 ½ hours to the city of Luang Prabang, and this will provide very little warning time for bank‐side residents to prepare for inundation by rapidly rising river levels. Tributary channels experiencing a backwater, such as the Nam Khan, will also experience rapidly rising water levels from turbine start‐up. Equally at risk will be downstream effects of rapidly falling levels, that may arise during the day or night when the electrical demand is low. In the low flow season and shoulder season, the dam operator/owner may decide to do peak power generation, with repeated fluctuations in the flow released during each 24 hour period. The best case scenario is that peak power generation will not be licensed, and that projects will be required to operate at continuous power production, with a resulting minimization of river level rapid fluctuations. Table 6.6: implications of peaking operation on water level fluctuations for three sample projects BAN KOUM PROJECT (70km LUANG PRABANG DAM (upstream of Luang Prabang town) upstream Pakse) STUNG PROJECT WLs WLs Daily WLs Averag Daily from Average from Average Flow from e Daily Flow rating Daily Daily Flow rating Daily Volum rating flow Volume curve flow Volume curve flow e curve (m3/s) (m3/d) (m) (m3/s) (m3/d) (m) (m3/s) (m3/d) (m) Peaking Operation rated turbine flow 3,800 11,700 18,493 Mean Annual Flow (MAF) at dam 3,171 Rated turbine flow/MAF 1.20 Off peak peak flow 1,900 5,850 280,800 9,247 91,200 443,832 peak flow 5,700 17,550 27,740 Continuous Operation 3,800 91,200 11,700 280,800 18,493 443,832 Additional flows (Dam site ‐ town) Nam Ou 492 11,796 ‐ ‐ ‐ ‐ ‐ ‐ Nam Soung + Nam Khan 181 4,338 ‐ ‐ ‐ ‐ ‐ ‐ Flow rate at town/gauging station Continuous 4,472 107,334 8.8 11,700 280,800 5.3 18,493 443,832 5.8 off peak 2,572 6.5 5,850 3.0 9,247 4.0 107,334 280,800 443,832 peaking 6,372 11.0 17,550 7.0 27,740 7.0 Mean annual flow MAF (BDP BS) 3,702 9,343 224,232 13,714 329,136 Rated turbine flow/MAF 1.21 1.25 1.35 Fluctuation (peaking ‐ offpeak) 3,800 4.5 11,700 4.0 18,493 3.0 92 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | HYDROLOGY & SEDIMENT Rapid fluctuations in river level will adversely affect the stability of river banks, as they will experience repeated wetting and drying. Enhanced erosion and collapse of river banks may be expected around the periphery of the reservoirs, and at specific locations downstream of the dams (see sediment transport issue, 2.1). Further unprecedented fluctuations in flow/level may arise from break‐downs, malfunctioning or operator error in controlling the spillway gates. With a failure of the primary and back‐up facilities to raise the spillway gates during the onset of the flood season, there is a significant risk of dam failure, and the release of flows of unprecedented magnitude at one or many of the dams. The best case scenario is that catastrophic releases of this type will not occur. A concerted effort will be needed for the establishment/enforcement and execution of a program of comprehensive dam safety reviews. Additionally station operating rules for staff at each project will have to be carefully prepared, and subjected to peer review prior to the start of operation (see Mitigation). FLOODING Changes in timing and levels of the seasonal hydrograph of the river resulting from the projects will be small, but may be significant. For example with the 10 projects in place and operating, the time delay of the arrival of the flood at Kratie will be an additional 2 weeks during an average precipitation year, and the duration of the flood season will be reduced by less than one week. TONLE SAP LAKE The major change from the Baseline for flooding in the Tonle Sap will occur as a result of the combined effect of tributary and Yunnan storage. There is likely to be no appreciable change from the LMB mainstream projects (see Figure 6). In summary, changes in water levels from the mainstream projects are expected to adversely affect market gardening along the Mekong River and in major and minor tributaries near the mainstream, the habitability of floating homes that are downstream of the dams, fish habitat, and the viability of water intakes/pump stations adjacent to the river and tributary mouths. 6.4.3 FATE AND TRANSPORT OF COARSE SIZED SEDIMENT Coarse sized sediment: There are highly likely risks that coarse sized sediment, e.g. coarse sand, gravel and larger sizes will accumulate in parts of the river where it has never accumulated in the past, for example in the headwater reaches of the ten proposed reservoirs. The amount of accumulation will depend on the sequencing of the construction of the proposed cascade, and on the contribution from immediately upstream tributaries. This component, together with medium sized sand, constitutes the majority of the bed load transport of the Mekong River. Essential the dams will create a series of obstacles to the bed load transport, and will cause delays, possibly of years or decades, in the downstream transport. With the expected localisation in stream power dissipation for the majority of the 1760 km distance from Pakbeng backwater to Sambor, there will be much reduced water power available to suspend particles and keep them moving. The result of this will be enhanced sedimentation, with the formation of deltaic type deposits at the head of each of the reservoirs. Deep pools that are in these head‐of‐reservoir areas 93 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | HYDROLOGY & SEDIMENT will be in filled. The severity of this problem is difficult to compute, as the deep pools are present in the Mekong mainstream because of complex three dimensional river currents, and the local topography of the bedrock on the sides and bottom of the river. Much enhanced sedimentation from coarse particles should also be expected where medium and high gradient tributaries enter the proposed reservoirs. The well established deep part of the river channel (the “thalweg”) that in many locations defines the international boundary (e.g. Thai‐Laos border) will be lost in many locations, due to sediment accumulation and erosion. This may or may not pose problems in the future for establishing/verifying the exact location of the international border. There are risks that sediment will erode from areas where is has never eroded in the past, for example immediately downstream of the proposed dams, and in bank side locations where the river thalweg is pushed sideways by a tributary delta entering the mainstream. Immediately below each of the dams it is likely that the flow will scour the river bed, probably down to bed‐rock at the majority of sites, and create new locations for the thalweg, depending on the flow alignment as it leaves the turbines and the spillways. For the low gradient alluvial reach (Zone 3) from upstream of Vientiane to near Savannakhet, there will be a trend towards down cutting of the river bed, with destabilization of banks. This trend will be caused partly by the proposed changes/dam construction in the river and its tributaries under the 20 year scenario, and the trend will be much accentuated by the proposed mainstream projects. The progression of this down cutting is hard to compute, as there are insufficient data on parameters such as particle size distribution that are needed to establish what is stored in the river bed. Mitigation of bank erosion problems may be undertaken with engineering works such as rip‐rapped embankments, but the cost of these per km is very high, and requires the proximity of a nearby rock quarry. For the lower river, Zones 5 and 6, there is low availability of coarse sediment in the mainstream, except at Kratie where there are dredges at work in the river channel extracting gravel sized material. 6.4.4 FATE AND TRANSPORT OF FINE SIZE SEDIMENT Fine sized sediment: Decreases in the concentration of suspended fine material (fine sand and silt particles) will arise in the mainstream channel, because some of this component will settle and be stored permanently on the bottom of the proposed reservoirs. With the expected low velocities in the reservoirs for the majority of the time, it is expected that sediment sizes equal to and larger than medium sand (about 0.3 mm grain size) will be trapped and settle to the bottom and backwater areas of the reservoirs. A proportion of the materials that are finer than medium sand will be carried to the bottom and permanently stored in the depositing sand layers. This trapping of sediment will primarily be an impact during the first decade of operation of the proposed mainstream dams, as it is likely that siltation will reach a long‐term equilibrium fairly quickly (one to two decades) because the reservoirs are relatively small. Prior to reaching equilibrium, there will be more fine sediment entering the reservoirs than leaving them, and this will diminish the load that is carried by the downstream river. The magnitude of the deposition is hard to compute, and will depend on the sequencing of construction of the mainstream dams, and fine sediment contributions from tributary rivers that enter the mainstream immediately upstream of the reservoirs. Figure 6.15 presents the relationship between reduction in sediment load and the trapping efficiencies of mainstream hydropower, which can be seen to be approximately logarithmic. The greatest reduction in 94 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | HYDROLOGY & SEDIMENT sediment load occurs within the first 10 TE percentage points, after which further reductions in sediment load begin to plateau such that there is only minor reductions in sediment load when trapping efficiencies increase greater than 40% (MRC, 2010). Consequently, even modest trapping efficiencies from the LMB mainstream project will contribute significantly to the reduced sediment load expected by 2030. Fig 6.15: Modelled relationship between LMB mainstream dam trapping efficiencies and reduction in Mekong sediment load (Source: MRC, 2010). Computations have been done for the Mekong dams on the basis of reservoir trapping efficiencies from other sites worldwide (figure 14) and these have shown that the LMB mainstream projects have individual trapping efficiencies of between 0 – 55% (Kummu et al, in publication). Given that the majority of further reduction in sediment load by the mainstream projects will occur within the first 40 TE percentage points, the mainstream reservoirs will have an impact on the future sediment load. To indicate the order of magnitude change, the current sediment load of the Mekong at Kratie is approximately 165million tonnes per year, the tributary projects and the Yunnan cascade are expected to reduce this by 60‐80% (i.e. 35‐70million tonnes/yr). Taking the lower limit and upper limit of the potential reduction from the mainstream projects (Fig 6.16) suggests that the 2030 sediment load with mainstream dams could be in the order of 20‐40million tonnes/year. This predicted reduction may be overestimated, because of major sediment flushing activities that are planned for the proposed dams near the turbine intakes. Better predictions cannot be done at the moment, because of insufficient data concerning the particle sizes of material in suspension in the river. 95 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | HYDROLOGY & SEDIMENT Figure 6.16: Mekong Basin hydropower trapping efficiencies with confidence intervals (Kummu et al, in publication). LMB mainstream projects are shown as squares on the left‐hand side of the diagram NUTRIENT TRANSPORT The decrease in the fine particle component of the suspended load has vital implications for the transport of nutrients (phosphorus, nitrogen and trace amounts of important minerals) onto the floodplain, and into the Tonle Sap system. Fine particles have much more surface area per unit volume than do coarse particles, and fine particles carry the majority of the nutrients that are needed by living systems. Natural fertilization from floodwaters that is important to about 18,000 km2 of the Cambodian floodplain (see Fuji et al39), will be impacted by reductions in the concentration of suspended fine particles. A well understood relationship for lake and river systems exists40,41 between nutrient transport, primary production, aquatic invertebrate success, and fish growth and condition, showing that reductions in nutrients will have impacts on fisheries. Additional impacts from the decrease in the transport of fine sediment will also arise at the mouth of the Mekong, with impacts on the offshore fishery which is partly dependent on the nutrients transported to the ocean environment by the Mekong sediment regime. 39 Fujii H., H. Garsdal, P.R.B. Ward et al 2003. Hydrological roles of the Cambodian floodplain of the Mekong River. Intl Journal of River Basin Management Vol 1, No 3 pp 1‐14. 40 Goldman C.R. and A.J. Horne 1983. Food‐chain Dynamics, Chapter 15 of Limnology. McGraw Hill, pp. 272‐291. 41 Mulholland, P. J. and D. Rosemond. 1992. Periphyton response to longitudinal nutrient depletion in a woodland stream: evidence of upstream‐downstream linkage. Journal North American Benthological Society 11:405‐419. 96 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | HYDROLOGY & SEDIMENT DELTA STABILITY The mainstream LMB projects pose a significant risk to the integrity of the delta coastline and the stability of the distributaries and deltaic fan which characterizes the delta. A significant reduction in deposition (due to reduced loading) and no significant change in erosion rates will see increased impacts of erosion with knock‐on effects for those living along the river channels and coastlines as well as in the sectors that utilize these resources, including: • Coastal fishery zones will experience reduced primary production with implications for the whole marine fisheries. Other industries in the fisheries sector which rely on waste products of the marine fishery for feed pellets and stock (e.g. aquaculture) are also likely to be affected. • Irrigation works may benefit from reduced sediment build‐up primary canals in the long term, however, this is likely to be overshadowed by greater instability in natural and man‐made channels. • Coastal erosion and delta‐building will undergo a shift in the current balance as existing coastal sediment dynamics are altered. Less sediment will wash along the eastern coast of the delta exacerbating the effects of erosion in these provinces and also reducing the rate of deltaic growth currently experienced by the Ca Mau peninsula. • River and inland water way transport may be effected as channel stability reduces • In‐channel islands, which are heavily populated and amongst the most fertile zones of the delta, are likely to experience greater erosion at the upstream end affecting communities and industries Figure 6.17: Indicative profile of suspended sediment profile with mainstream dams: (left) Kratie: reductions in sediment load will reduce the total load of sediment transport. The implications on grain size may be partially off‐set in the short term as increased erosion of the mainstream channel bed and banks compensates for reduced loading and re‐supplies some medium sized particles. In the long‐term this off‐set will not remain significant; (right) Tan Chau/Chau Doc: reductions in sediment load will see a significant reduction in the load of sediment arriving at the Delta with serious consequences for channel and coastal stability as well as nutrient supply to agricultural and fisheries activities. This cannot be off‐set by increased upstream entrainment of coarser materials as the floodplain system does not have the capacity to entrain these larger sized materials into the delta. 97 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | HYDROLOGY & SEDIMENT 98 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE 7 TERRESTRIAL ECOSYSTEMS & AGRICULTURE 7.1 STRATEGIC ISSUES • Habitat loss and degradation, forest cover and protected areas • Changes to patterns of agriculture • Value of paddy agriculture in each zone • Changes to agricultural and land use patterns along the mainstream, especially river bank gardens 7.2 SUMMARY OF PAST & FUTURE TRENDS WITHOUT LMB MAINSTREAM HYDROPOWER The terrestrial ecosystems surrounding the Mekong as represented by the landuse and forest cover, start from extensive forest cover in Zones 1 and 2, which decreases markedly as the river passes through zones 3, 4, 5 and 6; agricultural land use becomes progressively higher percentage, especially in NE Thailand, southern Laos, and below Kratie in Zone 5 and in the Delta. Government policies tend to be towards intensification of agriculture, with increased irrigation in Laos and Cambodia. In NE Thailand water for further irrigation is a limiting factor, and availability of suitable land is a limiting factor in the Vietnam Delta. The terrestrial ecosystems around the Mekong river are recognized as being globally important in terms of biodiversity and of 2600 km of the Lower Mekong, lengths of over 1000 km are considered as Key Biodiversity Areas, but only about 100 km of the river actually lies within a nationally protected area. River bank gardens have been recognized as an important contributor to the livelihoods of riparian communities, and although these have not been systematically studied, their contribution in each zone has been estimated of the order of 10 – 60 million US per year. 7.3 EXPECTED DIRECT EFFECTS OF THE PROPOSED LMB MAINSTREAM HYDRO PROJECTS 7.3.1 KBAS AND PROTECTED AREAS One of the indicators of the biodiversity impact of the proposed mainstream dams is the extent to which they and the reservoirs affect Key Biodiversity Areas and Protected Areas. Table 7.1 summarizes this indicator. Of the 1,100 km of Mekong River which is considered to be part of a Key Biodiversity Area, about 860 km (about 80%) will be directly affected by the presence of the reservoirs, usually by inundation of riparian vegetation and wetlands along the river. This will change the terrestrial habitat of the flora and fauna using these areas, especially congregatory water birds, for which many of these KBAs have been notified. About 79% of zone 2’s KBAs will be impacted, and 100% of zone 3’s and of zone 4’s KBAs will be impacted by the reservoirs. 99 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE Table 7.1: Impact of proposed dams and reservoirs on Key Biodiversity Areas (KBA) and Protected Areas in each Zone Zone Length of river Length of river Length protected Length Relevant dams KBAs and protected areas directly channel considered as KBA impacted by impacted reservoirs km km km km 1 220 >100 0 0 • Pak Beng, • Upper Lao Mekong, • Louangprabang 2 795 570 0 450 • Mekong channel upstream of • Sanakham, Vientiane, • Pak Chom • Mekong channel near Pakchom. • Pha Taem NP, 3 715 100 100 100 • Ban Koum • Phou Xiang Thong NPA, • Houay Kok/Houay Phalang IBA • Latsua (d'nstream) • Mekong Channel (Phou Xiang Thong • Don Sahong - Siphandone), 50 (includes Stung 4 310 310 310 • Thakho • Siphandone, Treng Ramsar site) • Stung Treng • Mekong river (Kratie to Lao border), • Sambor • Stung Treng Ramsar site, • proposed Dolphin special management zone 5a 335 0 0 0 5b Whole of Tonle Sap 14,812 km2 0 Various wetlands in 6 225 27,425 ha 0 floodplain Total 2,600 >1,100 150 860 100 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE Only about 150 km of the river is formally protected in a National Protected Area, and this length will be directly affected by Ban Koum reservoir which passes between Pha Taem National Park on the Thai side and Xiang Thong NPA on the Lao side. Although these areas were designated to protect the sandstone escarpments and forests, the river channel is a part of each country’s protected area system. The other length of formally designated area is the Stung Treng Ramsar Site, which extends from Stung Treng town nearly to the Laos border. Unlike other Ramsar sites in Cambodia, Stung Treng is not within a formal protected area. This is exactly the area that would be inundated by the proposed Stung Treng dam. With this active consideration of the proposed Stung Treng dam, the Ramsar Convention should be notified to put the Stung Treng Ramsar site on the Montreux Record of sites under threat. It is highly likely that the reservoir would destroy the rationale and criteria for the Ramsar designation. This would require a review of its designation, possibly leading to it being removed from the list of Ramsar Sites. However, there are also indirect impacts on KBAs and protected areas downstream. These are principally related to the changes in the hydrology of the Tonle Sap system. A comparison of the extent of the surface area of the Tonle Sap modeled under different BDP scenarios, (see hydrology theme paper) shows that under the 20year scenario with the mainstream dams the area inundated at the end of the dry season in May may increase by about 10% (250 sq km cf 2,500 sq km). Without the mainstream dams, there would be an increase of about 8% (200 sq km cf 2,500 sq km). In the wet season, September, the surface area is predicted to increase dramatically by about 700 sq km compared to the current average of 14,500 sq km. Most of this (about 650 sq km) is due to the shift in the hydrology caused by the Chinese and tributary storage dams, but there is a proportion due to the mainstream dams. The implication of this is that the Ramsar sites and flooded forests within the Tonle Sap system will be under threat. Higher water levels in both wet and dry season means that the flooded forests are “squeezed” – they can not expand in the landward side because of existing land use for agriculture, and the water side forests may no longer be viable because they will be inundated for longer. 7.3.2 AREAS INUNDATED The mainstream dams generally have small reservoirs associated with them, with the existing river channel making up the largest proportion inundated. The areas of wet season and dry season channels inundated has been covered in the aquatic ecosystems. Table 7.2 shows the areas of existing river channel, forest land and agricultural land inundated. 42 The 12 mainstream hydropower projects will have a total of over 151,000 ha of reservoir, of which 29% lie in Zone 2, 16% in zone 3 and 55% lie in Zone 4. 92,000 ha of existing river channel will be inundated (61% of the total reservoir area ‐ 59% in Zone 2, 84% in Zone 3 and 55% in Zone 4). Outside of the rive r channel, 23,000 ha of forest land (mostly degraded forest) will be inundated and 13,500 ha of agricultural land43. Of the agricultural land inundated, only a total of 829 ha of irrigated land will be inundated. Several of the mainstream dam projects are being designed to provide facilities for irrigation, some of which are quite significant. The key dams here are Pak Chom, Ban Koum and Latsua, whilst information on the irrigation potential for the Cambodian dams is not yet available. Thus Pak Chom has plans for 11 irrigation 42 These figures are derived from the IEEs and EIAs of the mainstream dams, summarized in Volume 2 of the SEA Inception report 43 Note that figures forest and agricultural land inundated for Stung Treng are not yet available so the total areas will be higher than this 101 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE schemes around the area, covering a total of 2,706 ha of which 1 scheme (217 ha) is in Laos and 10 schemes (2,489 ha) are in Thailand. At one stage Pak Chom was identified as the source of the offtake for the Thai mega‐project for transfer of water to NE Thailand, but consideration of this is not included in this SEA. Ban Koum, also shared with Thailand, has a plan for the irrigation of a total of 7,870 ha of which 8 schemes are in Laos and 14 in Thailand. Latsua has similar sized irrigation plan for developing irrigation of 7,300 ha for 3 crops per year in Laos which is currently under feasibility study. When the productivity of the areas inundated is considered and compared with the proposed irrigation schemes associated with at least 3 of the dams, it can be seen from Table 7.4 that, in Zone 2, the lost annual productivity due to the inundation by the reservoirs would have a value of 1.15 million USD, 1.17 Million USD in Zone 3 and 1.77 million USD in Zone 4. When the proposed irrigation schemes are put in place, the value of the increased productivity is 1.89 million USD per year in Zone 2 and 13.65 million USD per year in Zone 3. No figures are available for irrigation potential from the Cambodian dams. It can be seen that even with just three dams being used for irrigation as well as hydropower, the gains more than outweigh the losses in each zone. 7.3.3 ACCESS ROADS AND TRANSMISSION LINES The footprint of the dams not only includes the areas of land inundated, but also the provision of access roads for the construction and operation of the dams and the transmission lines to link the mainstream dams with the regional electricity grids. Table 3 shows the current state of information about these, showing that the additional transmission lines would require over 1,542 km of access corridor. Assuming that this corridor is 70 m wide, the total land occupied would be an additional 10,794 ha. Without the detailed analysis of routes it is difficult to say what proportion of forest or agricultural land that these corridors would traverse, or passage through protected areas, however an estimate can be made by taking the proportions of forest and cultivated land in the 50 km corridor on each side of the Mekong mainstream. This shows that a total of at least 7,886 ha of forest land and 2,286 ha of cultivated land would be affected in the 50 km corridor on either side of the Mekong. Map 1 shows the 500 kVa transmission lines planned for the GMS into which the transmission lines from the proposed dams will connect. The losses in paddy production 44 as a result of the transmission lines are shown in Table 7.3 and range from annual losses of 0.36 million USD for Zone 2, 0.89 million USD for Zone 3 and 0.06 million USD for Zone 4. Note that these are low figures because data on lengths of transmission lines are not available yet. In terms of access roads that will have to be provided for construction of the dams, there is insufficient data at this stage to make a meaningful comment, although the distances are not anticipated to be very large for each dam. Road upgrades on the Laos side have already improved access for a number of dam sites, namely, Pak Chom and Sanakham, Ban Koum and Latsua, so additional access roads are likely to be purely local for these. In addition a number of dams will construct temporary bridges across the Mekong mainstream and some of the tributaries, e.g. Pak Beng and Louang Prabang (across the Nam Ou) and once constructed, the dam itself may provide crossing points across the Mekong. 44 Losses due to the transmission lines assume that all the land under the transmission line will be paddy land. This will not be the case, but the estimate serves as a first order of magnitude) 102 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE Figure 7.1: Proposed transmission lines for the GMS with connections to proposed dams (Source: International Rivers, based on ADB, map to be revised) 103 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE Table 7.2: Areas of land inundated by each reservoir associated with the proposed Mekong mainstream dams and associated irrigation schemes River Zone Area of channel Length of River Land inundated Irrigation schemes proposed no. Ecological Zone Dams reservoir inundated section reservoir Forest Agriculture Irrigated Laos Thailand Cambodia km km ha ha ha ha ha ha ha ha China to Chiang 1 2,120 Saen Chinese dams Pak Beng 160.0 8,700 7,000 400 1,325 332 0 Louangprabang 147.0 7,239 2,864 4,181 194 0 0 Xayaburi 95.0 4,900 4,720 162 18 0 0 Chiang Saen to Pak Lay 110.0 7,000 2,310 2,180 665 165 0 Vientiane Sanakham 97.0 8,000 2,000 not available 6,000 not available 0 Pak Chom 85.0 7,354 6,750 387 217 not available 217 2,489 1 scheme 10 schemes TOTAL Zone 2 dams 795 694.0 43,193 25,644 7,310 8,419 497 Ban Koum 149.0 15,800 13,600 1,874 343 na 7,870 Vientiane to Pakse 8 schemes 14 schemes Latsua 10.0 8,700 7,000 400 1,325 332 7,300 TOTAL Zone 3 dams 713 159.0 24,500 20,600 2,274 1,668 33 2 Don Sahong 5.0 290 93 173 30 0 0 Thakho N/A 0 0 16 14 0 under consideration Pakse to Kratie Stung Treng 52.0 21,100 not available not available not available not available not available Sambor 86.0 62,000 45,480 13,143 3,369 not available not available TOTAL Zone 4 dams 330 143.0 83,390 45,573 13,332 3,41 3 0 Kratie to Phnom 5 Penh and Tonle Sap 3640.00000 0 Phnom Penh to the 6 sea 2250.00000 0 Lower Mekong Total 2,427 996 151,083 91,817 22,916 13,500 829 104 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE Table 7.3: Land requirements for transmission lines and access roads for the mainstream dams (as far as is currently available) Zone Access no. Ecological Zone Dams Transmission line required roads Total Area required Area @70m Area of cultivated Length Destination corridor forest land land km km ha ha ha 1 China to Chiang Saen Chinese dams Pak Beng na Thailand na na na 15.6 Louang Prabang 400 Vietnam 2,800 2,265 445 15 Xayaburi 220 Thailand 1,540 1,246 24425 2 Chiang Saen to Vientiane Pak Lay na Thailand na na na na Sanakham na Thailand na na na na Pak Chom 185 Thailand 1,295 1,048 206 na TOTAL Zone 2 dams 805 5,635 4,559 895 Ban Koum 434 Thailand 3,038 1,551 1,270 na 3 Vientiane to Pakse Latsua na Thailand na na na na TOTAL Zone 3 dams 434 3,038 1,551 1,270 Don Sahong 21 Thailand 147 123 8 5 Thakho 22 Laos 154 129 92 4 Pakse to Kratie Stung Treng na Vietnam na na na na Sambor 260 Vietnam 1,820 1,524 104na TOTAL Zone 4 dams 303 2,121 1,776 122 Kratie to Phnom Penh 5 and Tonle Sap 6 Phnom Penh to the sea Lower Mekong Total 1,542 10,794 7,886 2,286 62.6 105 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE Table 7.4: Value of rice production lost from agricultural land inundated and gained from associated irrigation schemes and transmission lines Zone 1 2 3456 Kratie to China to Phnom Chiang Saen Vientiane Pakse to Phnom Chiang Penh to to Vientiane to Pakse Kratie Penh and Saen the Sea Unit Tonle Sap Paddy field area in 50 km corridor of river sq.km 500.22 3,655.09 22,916.31 1,625.64 13,910.25 19,810.05 Yield t/ha/yr 1.00 2.00 3.50 2.60 2.60 5.00 Annual production t/yr 50,022 731,019 8,020,710 422,666 3,616,666 9,905,024 Value @ 0.2 $US/kg US$ million 10.00 146.20 1,604.14 84.53 723.33 1,981.00 With mainstream dams Inundated agricultural land ha 0.00 2,882.00 1,668.00 3,413 0.00 0.00 loss of production t/yr 0.00 5,764.00 5,838.00 8,872.50 0.00 0.00 Lost Value @ 0.2 $US/kg US $ million 0.00 1.15 1.17 1.77 0.00 0.00 With associated irrigation Area of irrigation scheme developed ha 0.00 2,696 15,170 na 0.00 0.00 Yield t/ha/yr 0.00 3.5 4.5 na 0.00 0.00 Production t/yr 0.00 9,436 68,265 na 0.00 0.00 Value of annual production US $ Million 0.00 1.89 13.65 na 0.00 0.00 Losses due to transmission lines Areas of cultivated land lost in 50 km corridor ha 0.00 895 1,270 122 0.00 0.00 Yield t/ha/yr 0.00 2.00 3.50 2.60 0.00 0.00 Lost production t/yr 0.00 1,789 4,444 316 0.00 0.00 Value of lost annual production US $ Million 0.00 0.36 0.89 0.06 0.00 0.00 (note that transmission lines lengths ar not available for all dams, so this is an underestimate of the losses) 106 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE 7.3.4 IMPACTS UPON LAND USE ‐ FOREST COVER AND AGRICULTURE A GIS analysis of the impacts of land use (carried out for this SEA) has considered the areas inundated by all of the dams and expressed in comparison to the total areas of different landuses within a 50 km corridor on each side of the Mekong. Maps 7.1 – 7.7 show the inundation areas nearest to some of the mainstream dam sites. It is clear from these maps that the inundation is largely within the river channel in most cases, except for the lowest two dams. Even near the dam sites, relatively little land is inundated. Table 6 shows this comparison for all of the dams proposed along the Lower Mekong. From this table it is clear that of the 1,371 sq km inundated the largest % losses due to the dams are wetlands, of which a total of 735 sq km will be modified into reservoirs. This makes up 54% of the area inundated and mostly consists of natural water bodies, i.e. the river channel. This loss amounts to about 7% of the wetlands within the 50 km corridor. The next largest land use type to be inundated is forest – mostly evergreen and deciduous, with about 544 sq km inundated (about 40%). This amounts to about 0.5% of the forest land cover in the 50 km corridor. Agricultural land inundated is relatively small, making up about 64 sq km (under 5%) or 0.08% of the agricultural land in the 50 km corridor. The indication from these overall figures is that the different land uses inundated are relatively small in comparison to the wider area. Zone 2: When the different zones are considered, the cascade of dams above Vientiane, makes a significant impact upon the wetlands in Zone 2. Table 7.7 shows that 52% of all the wetlands in Zone 2 will be modified into reservoirs. This is a dramatic change also described in the aquatic impacts paper. The forest cover in zone 2 amounts to about 91 sq km, which is about 0.2% of the forest cover in the 50 km corridor on each side of the Mekong. Agricultural land inundated amounts to nearly 10 sq km or 0.12% of the total agricultural land in the zone 2 50 km corridor. The dams in zone 3 (shown in table 8), will inundate 112 sq km. of wetlands amounting to about 6% of the total wetland area in the zone. About 0.1% of the forest land will be inundated and 0.02% of the agricultural land in the zone 3. In Zone 4, the dams will inundate 335 sq km, or about 17% of the total wetland area in the 50km corridor of the zone. This is also a significant proportion implying a great change in the landscape character of the zone. This is made up about 35% of the natural water bodies, i.e. the river channels, and significantly about 3% of the flooded forests in the Zone 4. About 425 sq km of other forest will be inundated, making up about 1.63% of the forest in the corridor. It is not possible to distinguish beyond the major categories of deciduous, and evergreen forest and bamboo, but it should be noted that the first type of forest to be lost will be the characteristic types that grow along the river banks, and these will not be replaced along the reservoir banks. River bank vegetation is clearly different from the trees further up the hillsides. Zones 5 and 6 will not be affected by the inundation caused by the dams. 107 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE Table 7.5: Comparison of landuse in 50 km corridor along each bank of Lower Mekong with areas inundated by mainstream dams Total all Total all % land use Land Use type zones dams inundated sq.km sq.km Paddy field 62,418 50.9 0.08 Orchard 534 1.8 0.33 Field crop 9,937 8.6 0.09 Swidden cultivation 2,675 2.2 0.08 Total cultivated land 75,563 63.5 0.08 % cultivated land 4.63 Industrial plantation 2,611 0.0 0.00 Forest plantation 74 0.0 0.00 Bamboo forest 4,315 34.7 0.80 Coniferous forest 11 0.0 0.00 Deciduous forest 51,169 264.4 0.52 Evergreen forest 58,485 244.4 0.42 Total forest cover 116,666 543.5 0.47 % forest 39.62 Barren land 1,518 3.7 0.25 Grassland 6,797 23.8 0.35 Shrubland 11,839 0.9 0.01 Total open land 20,155 28.4 0.14 % open land 2.07 Flooded forest 1,725 39.1 2.27 Mangrove forest 147 0.0 0.00 Marsh and Swamp 556 0.9 0.16 Natural Water body 7,979 694.5 8.70 Aquaculture 777 0.0 0.00 Total wetlands 11,184 734.6 6.57 % wetlands 53.5 Built‐up area 5,424 1.758 0.03 % Built‐up 0.13 TOTAL 228,992 1371.7 0.60 108 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE Figure 7.2: Riparian vegetation and river bank gardens in the area affected by Louang Prabang reservoir Figure 7.3: Degraded forest along the banks near Pak Lay 109 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE Figure 7.4: Mature riparian trees along the Mekong upstream of Sanakham dam site Figure 7.5: Riparian vegetation around the Ban Koum dam site 110 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE Figure 7.6: The character of the landscape around Ban Koum will be changed by the reservoir (view from Pha Taem National Park, Thailand) 111 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE Table 7.6: Landuse types inundated by the Mekong mainstream dams in zone 2 China to Chiang Saen Land Use type Chiang Saen to Vientiane Zone 2 dams Louangprab Zone 1Zone 2Pak Beng Xayaburi Pak Lay Sanakham Pak Chom Total Zone 2% of zone ang sq.km sq.km sq.km sq.km sq.km sq.km sq.km sq.km sq.km Paddy field 500 3,655 0.538 0 0.055 0 0.074 1.333 2 0.05 Orchard 14 421 0 0 0 0 0 1.754 1.754 0.42 Field crop 123 3,4193.865000003.8650.11 Swidden cultivation 177 1,000 2.078 0.027 0.092 0 0 0 2.197 0.22 Total cultivated land 815 8,495 6.48 0.03 0.15 0.00 0.07 3.09 9.82 0.12 % cultivated land 8.91 15.8 8 7.74 0.04 0.30 0.00 0.11 4.07 2.50 Industrial plantation 0 51000000 00.00 Forest plantation 0 0000000 00.00 Bamboo forest 18 1,869 0 0 0 3.033 2.905 0.055 5.993 0.32 Coniferous forest 0 0000000 00.00 Deciduous forest 4,993 16,800 2.679 2.557 0.997 3.474 3.102 0.092 12.901 0.08 Evergreen forest 3,117 24,567 13.191 21.351 13.563 10.829 7.455 5.751 72.14 0.29 Total forest cover 8,128 43,288 15.87 23.91 14.56 17.34 13.46 5.90 91.03 0.21 % forest 88.91 80.9 0 18.95 39.02 29.38 32.80 19.36 7.78 23.18 Barren land 0 6 0 0 0 1.072 2.017 0 3.089 55.88 Grassland 123 575 0 0 0.141 0.002 0 0 0.143 0.02 Shrubland 0299 000000 00.00 Total open land 123 880 0.00 0.00 0.14 1.07 2.02 0.00 3.23 0.37 % open land 1.35 1.64 0.00 0.00 0.28 2.03 2.90 0.00 0.82 Flooded forest 0 0000000 00.00 Mangrove forest 0 0000000 00.00 Marsh and Swamp 0 27000000 00.00 Natural Water body 46 521 60.067 37.335 34.709 34.448 54 66.569 287.128 55.10 Aquaculture 0 4000000 00.00 Total wetlands 46 552 60.07 37.34 34.71 34.45 54.00 66.57 287.13 52.06 % wetlands 0.50 1.03 71.74 60.94 70.04 65.17 77.64 87.78 73.10 Built‐up area 30 2961.30900000.2811.590.54 % Built‐up 0.33 0.55 1.56 0.00 0.00 0.00 0.00 0.37 0.40 0.00 TOTAL 9,142 53,510 83.73 61.27 49.56 52.86 69.55 75.84 392.80 112 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE Table 7.7: Landuse types inundated by the Mekong mainstream dams in zones 3 and 4 Kratie to Phnom Vientiane to Pakse to Phnom Land Use type Zone 3 dams Zone 4 dams Penh to the Pakse Kratie Penh and Sea Tonle Sap Don Stung Zone 3 BanKoum Latsua Total Zone 3% of zone Zone 4 Sambor Total Zone 4% of zone Zone 5Zone 6 Sahong Treng sq.km sq.km sq.km sq.km sq.km sq.km sq.km sq.km sq.km sq.km sq.km Paddy field 22,916 2.77 1.39 4.16 0.02 1,626 0.084 9.509 35.15 44.743 2.75 13,910 19,810 Orchard 95 00 00.000 000 00.005 0 Field crop 2,467 0.172 0 0.172 0.01 92 0 1.056 3.53 4.586 5.01 2,318 1,518 Swidden cultivation 38 00 00.0065 000 00.001,265 130 Total cultivated land 25,516 2.94 1.39 4.33 0.02 1,782 0.08 10.57 38.68 49.33 2.77 17,497 21,458 % cultivated land 41.80 2.23 10.67 2.99 5.73 2.91 5.52 6.05 5.92 41.24 67.50 Industrial plantation 1,329 00 00.00537 000 00.00693 0 Forest plantation 0 00 00.000 000 00.000 74 Bamboo forest 105 00 00.00932 0 11.682 17.041 28.723 3.08 1389 3 Coniferous forest 9 00 00.003 000 00.000 0 Deciduous forest 13,801 14.75 0.34 15.09 0.11 13023 0.67 32.58 203.17 236.41 1.82 2549 3 Evergreen forest 15,932 9.71 3.03 12.74 0.08 11527 0.22 42.55 116.76 159.53 1.38 3339 3 Total forest cover 31,176 24.46 3.37 27.83 0.09 26022 0.89 86.81 336.97 424.67 1.63 7970 82 % forest 51.07 18.52 25.86 19.17 83.73 30.67 45.34 52.69 50.93 18.79 0.26 Barren land 1,342 0.65 0 0.65 0.05 13 000 00.00103 54 Grassland 243 0.56 0 0.56 0.23 223 0 14.35 8.772 23.122 10.38 4,067 1,566 Shrubland 589 0 0.02 0.02 0.00 999 0 0.066 0.774 0.84 0.08 9,046 907 Total open land 2,174 1.21 0.02 1.23 0.06 1234 0.00 14.42 9.55 23.96 1.94 13,217 2,527 % open land 3.56 0.91 0.15 0.85 3.97 0.00 7.53 1.49 2.87 31.15 7.95 Flooded forest 16 00 00.001016 0 12.027 27.117 39.144 3.85 305 388 Mangrove forest 0 00 00.000 000 00.000 147 Marsh and Swamp 344 00 00.00156 0.892 0 0 0.892 0.57 26 3 Natural Water body 1,419 103.32 8.25 111.56 7.86 844 1.03 67.63 227.17 295.82 35.04 3,382 1,766 Aquaculture 7 00 00.000 00 00.000 766 Total wetlands 1,786 103.32 8.25 111.56 6.24 2017 1.92 79.66 254.28 335.86 16.65 3,714 3,069 % wetlands 2.93 78.22 63.32 76.88 6.49 66.42 41.61 39.76 40.28 8.75 9.66 Built‐up area 396 0.168 0 0.168 0.04 23 000 00.0026 4,654 % Built‐up 0.65 0.13 0.00 0.12 17.87 0.07 0.00 0.00 0.00 0.00 0.00 0.06 14.64 TOTAL 61,048 132.09 13.03 145.12 31078 2.89 191.45 639.48 833.82 42,423 31,791 113 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE Table 7.8: Estimates of losses of values of river bank gardens due to reservoirs in each zone Length of River River Number of Yield of zone dependent River dependent HH per zone Average Total area Present vegetable affected rural dependent HH affected % of HH with RBGs area of of RBG Yield of produced Yield of Length by population HH within by using affected by RBG per lost due to vegetables after dams Vegetables Total value No. Ecological Zone of zone reservoirs (2005) 15 km reservoirs RBGs reservoirs HH reservoirs produced constructed lost lost per year @0.6 kg/sq.m @$0.8/kg ha ha Tonnes US $ million China to Chiang 1 2120 0 Saen NA No change Chiang Saen to 2 795 694 Vientiane 313,939 62,788 54,811 14 7,564 0.25 1,891 12,997 1,651 11,346 9.08 Vientiane to 3 713 159 Pakse 1,343,182 268,636 59,906 13 7,488 0.25 1,872 50,369 39,137 11,232 8.99 4 Pakse to Kratie 330 143 232,397 46,479 20,141 11 2,216 0.25 554 7,669 4,346 3,323 2.66 Kratie to Phnom 5 Penh and Tonle 364 0 Sap 3,581,952 716,390 No change 7 49,431 0.25 12,358 74,146 74,146 0 0.00 Phnom Penh to 6 225 0 the sea 6,482,368 1,296,474 No change 29 381,163 0.25 95,291 571,745 571,745 0 0.00 NB. These estimates do not include the losses due to difficulties of cultivating river bank gardens downstream of dams 114 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE 7.3.5 RIVER BANK GARDENS When the dams are constructed and the reservoirs come up their operating levels, there will no longer be significant seasonal variation in the water levels in the reservoirs. There may be daily variation of one to two metres depending upon operating mode of the dam. This effectively means that no river bank gardening, which depend upon the seasonal recession of the water after the high flows, will be possible within the reservoir areas. In addition to this the daily flow variations below each of the dams may mean that river bank gardening downstream of the dams may be difficult and risky for at least 25 km downstream of each dam, if not further. Impacts of downstream river bank gardens have not been estimated. Using the baseline estimates developed for the values of river bank gardens in each zone, Table 7.9 shows the calculations in losses in production from river bank gardening as a result of the reservoirs. This comes to a total of USD 20.72 million per year within zones 2, 3 and 4. This is most significant in Zone 2 and 3, with losses of about USD 9 million per year each. In Zone 2, where about 80% of the length of the river is converted to reservoir, so that the large majority of river bank gardening households will lose this livelihood source, and in Zone 3, where there is a higher density of households using river bank gardens, although the length of river bank affected is smaller. It is possible that alternative measures may be developed for reservoir bank cultivation, but it is unlikely that this will be as productive as normal river bank gardens, because they will no longer receive the nutrients brought down in the flood sediments. Figure 7.7: River bank gardens at i) Savannakhet, ii) Siphandone and iii) at Latsua dam site 115 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE 116 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE 7.3.6 OTHER IMPACTS UPON AGRICULTURAL LAND Apart from the areas of irrigated land inundated or created as a part of these schemes, it is possible that there may be a number of impacts upon agricultural land along the Mekong. Many of these are dealt with in other sections, especially the hydrology and social sections and so are only highlighted here. These include: • Increased water levels in the reservoir will present both opportunities and risks to irrigation. On the one hand, many pump sets and pumphouses may need to be relocated to higher ground in order to avoid being drowned. On the other hand, the increased water levels would provide a reduced pumping head for ongoing operations, though pumps may need to be resized to take advantage of these improvements in efficiency (see hydrology paper). • Variable water levels downstream of dams depending upon discharges, may mean more complicated pumping for irrigation that has to take into account variable levels • Elevated water levels in reservoirs may mean an increase in the ground water levels around and downstream of dams. This may be beneficial for water sources based upon pumping from wells, since pumping efficiencies would be increased and costs reduced. • However, increased ground water levels around dams, can also lead to mobilization of contaminants in the soil, for example arsenic, resulting in contamination of ground water sources. High arsenic levels have been recorded in Cambodia, especially around the Sambor dam and reservoir. • In the Delta, it is likely that under the Definite Future with the Chinese and tributary dams and under the 20 yr scenario with the mainstream dams, there will be a decrease in the flooded area, in the duration of flood and the depth of flooding, compared to the baseline. There is a marginal decrease in these changes when the scenario with the mainstream dams is compared to without the mainstream dams. There is thus likely to be little difference in wet season cultivation in the flood plain. • The increased dry season flows predicted for both the definite future and with the mainstream dams may have beneficial impact upon saline intrusion and acid sulphate release from soils. There is a marginal increase in the projected longer dry season with higher flows as a result of the mainstream dams. However, the Delta has a highly managed water system and the realization of these benefits in managing saline intrusion and acid sulphate soils may depend upon the effectiveness of this management. • The fertility of the floodplains depends to a large extent on the nutrients associated with the fine sediments carried down by the river, and deposited in the flood plain. It is probable that most of these fine sediments will pass through the mainstream dams and so this benefit will not be affected. 117 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE Figure 7.8: Proposed irrigation schemes associated with the proposed Pak Chom project 118 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE 7.4 SENSITIVITY ANALYSIS OF DAM GROUPINGS In undertaking this sensitivity analysis, two questions are considered: • What will be the critical changes arising from the group of dams in their own location compared to the overall Mekong terrestrial ecosystem and agriculture? • What will be the critical changes arising from the group of dams on other parts of the Mekong terrestrial ecosystem and agriculture? 7.4.1 CASCADE OF 6 DAMS UPSTREAM OF VIENTIANE If the upper cascade of six dams were installed alone, the changes to the landscape and terrestrial ecosystems of Zone 2 would be significant. Large parts of this zone are considered to be Key Biodiversity Areas, although none are actually protected as nationally protected areas. The cascade of dams will change the landscape in the Mekong valley, converting about 55% of the natural water bodies of the zone into inundated reservoir. Impacts upon the agricultural and forestry systems of the area are limited. There would be some relatively small losses of agricultural productivity, but this would be more than offset by the proposed irrigation schemes associated with Pak Chom dam. In terms of lost production of river bank gardens in Zone 2, the losses due to inundation are estimated at about 9 million USD per year which amounts to over 90% of the total Mekong river bank production in Zone 2. The dams in this cascade will have little influence upon the terrestrial ecosystem and agriculture in zones lower down in the river. Essentially terrestrial impacts of these dams are restricted to the zone in which they occur. 7.4.2 MIDDLE MEKONG DAMS The two dams in the middle reaches of the Mekong, Ban Koum, shared between Thailand and Laos, and Latsua which lies completely in Laos, have a significant impact upon the protected areas and key biodiversity areas in Zone 3. Ban Koum dam in particular is located between two national protected areas in Thailand and Laos, and whilst a small proportion of the terrestrial ecosystem will be inundated, the landscape in this sensitive and touristically important area will be changed significantly, from a seasonally variable river landscape to reservoir. The losses of inundated agricultural land are relatively small, and substantial irrigation schemes are associated with both dams, which will increase agricultural production in the zone by more than 10 times the lost production due to inundation. The losses in terms of production of river bank gardens are estimated at about 9 million USD per year. This is about 22% of the total production from Mekong river bank gardens in the Zone 3. The dams in Zone 3 will have little influence upon the terrestrial ecosystem and agriculture in zones lower down in the river. Essentially terrestrial impacts of these dams are restricted to the zone in which they occur. 119 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE 7.4.3 LOWER MEKONG DAMS (CAMBODIAN DAMS) As with the aquatic ecosystems impacts, the significance of the dams in the lower part of the Mekong in Cambodia, is that they would inundate one of the richest and most biodiverse areas of the entire Mekong system, an area which is of global importance to terrestrial as well as aquatic biodiversity. This is a unique area with interrelated aquatic and terrestrial ecosystems, serving a diverse range of land based flora and fauna. The Ramsar site established at Stung Treng, is important for its birds and mammals as well as its fish, and the area between Kratie and Stung Treng provides important habitat for hog deer and other mammals as well as the Irrawaddy Dolphin. There will also be loss of important flooded and riverine forests that are unique and can not be replaced or found elsewhere. In terms of agricultural land there will be a loss of a relatively small amount of agricultural production, but it is not known if there will be compensatory irrigation schemes. In terms of river bank garden production, about 45% of the current production will be lost, estimated at a value of 2.7 million USD per year. The Cambodian dams will have little influence upon the terrestrial ecosystem and agriculture in the zones above. However, Stung Treng and Sambor dams do have the potential to influence the terrestrial and agricultural ecosystems in the zones below, principally because of the influence upon the hydrology, flooding patterns and sediment distribution in the floodplain. The additional changes in hydrology are likely to be small in comparison to the changes occurring as a result of the Chinese and tributary dams, (i.e. the definite future) but these will affect the grassland ecosystems in the Cambodian floodplains and flooded forests in the Tonle Sap (see hydrology and aquatic impacts paper). 7.5 POSSIBLE INDIRECT LINKS WITH OTHER THEMES The impacts upon the terrestrial ecosystems and agriculture along the Mekong have a direct relevance to the social themes and the livelihoods of riparian communities. In particular the river bank gardens are often an essential component of riparian communities, providing both a source of income and essential subsistence crops – vegetables, fruits, tobacco etc. In addition, the direct loss of agricultural land due to inundation by the reservoirs, will mean a loss of income and/or rice production will affect these riparian communities. Even though there may be overall increases in rice production due to new irrigation schemes in each zone, the distribution of these benefits will be limited to some of the riparian communities near only 3 of the dams, rather than being spread evenly over all of the dams. These have implications for both social and economic themes. The losses to biodiversity and the changing landscape of major portions of the river valley, in all three zones (2, 3 and 4) will have negative impacts upon the tourism potential and attractiveness of these zones. The losses of forestry resources and terrestrial resources due to the transmission lines may be locally important, but without specific alignments it is difficult to define their importance. 7.6 SUMMARY OF IMPACTS ON TERRESTRIAL ECOSYSTEMS AND AGRICULTURE The Mekong mainstream dams will have a significant local impact upon the terrestrial ecosystems and agriculture in the areas of inundation. There will be little impact outside the areas of inundation and land take for transmission lines and access roads. The reservoirs inundate the river channel, with some smaller 120 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE areas of forest and cultivated land inundated along the river banks for most of the dams. The two Cambodian dams differ in that they will flood larger areas, including forest and cultivated land. However, the reservoirs will change the landscape of the Mekong river valley, maintaining the water levels slightly above the current high flow levels, with little seasonal changes. This will have an impact upon the terrestrial biodiversity which is considered to be significant – about half the length of the Lower Mekong has been recognized as Key Biodiversity Areas (even though only a small length in Zone 3 is a part of a National Protected Area), and the river above Stung Treng is a designated Ramsar Site. Significant parts of the Key Biodiversity Areas will be affected by the dams. Small areas of cultivated land will be lost, but the total loss in production will be more than recovered by irrigation schemes in three of the dams. River bank gardens in the reservoir areas will be lost, with some significant impacts on livelihoods of riparian communities. 7.7 MAPS Figure7.9: Zone 2 ‐ Extent of inundation on land use by Louang Prabang dam (nearest the dam) 121 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE Figure 7.10: Zone 2 ‐ Extent of inundation on land use by Pak Lay dam (nearest the dam site) Figure 7.11: Zone 2 ‐ Extent of inundation on land use by Pak Chom dam (nearest the dam site) 122 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE Figure 7.12: Zone 3 ‐ Extent of inundation on land use by Ban Koum dam, (nearest the dam site) Figure 7.13: Zone 3 ‐ Extent of inundation on land use by Latsua dam 123 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | TERRESTRIAL & AGRICULTURE Figure 7.14: Zone 4 ‐ Extent of inundation on land use by Stung Treng dam Map 7.15: Zone 4 ‐ Extent of inundation on land use by Sambor dam 124 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS 8 AQUATIC SYSTEMS 8.1 STRATEGIC ISSUES • Productivity of aquatic habitats in the Mekong • Biodiversity of aquatic habitats in the Mekong • The capacity of the Mekong’s ecosystem regulating services – purification and water quality • Value of Mekong River’s cultural ecosystem services – inspiration, recreation and tourism 8.2 SUMMARY OF PAST AND FUTURE TRENDS WITHOUT LMB MAINSTREAM HYDROPOWER The aquatic ecosystems of the Mekong are relatively natural at the moment, with high diversity of aquatic habitats – rapids, deep pools, sandbars etc. that all contribute to the very high biodiversity in the river. There have been some changes in recent years, e.g. the development of two upstream dams in China, and on some of the tributaries in the LMB, that have begun to alter the hydrology and patterns of sediment discharge, so that the river morphology is beginning to change. As these developments increase in size and number, so this process of change will continue in the absence of the mainstream dams. Whilst the river is relatively clean and in good ecosystem health at present, there are increasing point sources of pollution, e.g. urban areas, and dispersed sources, e.g. agricultural run‐off, these are mitigated by the large dilution effect of the river flow. However there are signs of decreasing water quality and these are expected to increase in the future with growth of population. The Mekong is recognized as having an immense cultural value for the riparian cities and communities and for tourism. The tourist attraction of a large, dramatic, near‐natural river, a feature of the GMS tourism strategy, is expected to continue to increase in the future. 8.3 EXPECTED DIRECT EFFECTS OF THE PROPOSED LMB MAINSTREAM HYDRO PROJECTS The first task in this assessment of impacts of the mainstream dams is to develop an understanding of the key changes that are likely to take place as a result of their construction and operation. These are described generically and then cumulatively for all 12 hydropower schemes. Finally a sensitivity analysis is carried out on three groups of dams – the cascade above Vientiane, from Vientiane to Siphandone, and from Siphandone to Kratie – these relate to Zones 2, 3 and 4. 8.3.1 CONSTRUCTION IMPACTS If the dams are approved, as currently scheduled in MOUs the cascade upstream of Vientiane would be commissioned (i.e. constructed and operating commercially) by 2016. The dams at Sanakham, Pak Chom and Latsua are scheduled for commissioning between 2017 and 2018. Don Sahong and Thakho diversion are scheduled for completion by 2016 and Sambor by 2020. There is no date provided yet for Stung Treng. It is almost inevitable that many of these commissioning dates will slip, if only because the approval process for the first set of dams will be prolonged into 2011 or 2012. However, for the purposes of this assessment, the construction of all 12 hydropower schemes is likely to extend for the next 10 – 15 years. Therefore the construction impacts will be felt on the Mekong aquatic ecosystems for at least this period. There would in addition be a transition phase of at least 5 years after the dams are constructed, whilst the aquatic ecosystem 125 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS adjusts to the changed conditions. It is therefore safe to say that construction impacts will be felt in different parts of the river to at least 2030. The key changes that will be felt during the construction period are: • Increased release of sediment from construction activities, earth moving, tunneling, road construction along the river bank • Increased risk of pollution from construction camps, stores and construction activities, including organic waste from sewage, spillage of oil and fuel, accidental release of toxic construction materials, with consequent kills of fish and other aquatic animals. • Changes in flow as parts of the river are diverted past coffer dams and tunnels, and in the end during the filling of the reservoirs, although this will be relative short process for run‐of river dams • Changes in water quality as a result of breakdown of vegetation in the reservoirs, although this is expected to be relatively small because of the small footprints of the reservoirs, most of which lies in the mainstream channel • Blockage of key sections of the river for fish movement and migration, both as a result of physical barriers, such as temporary and permanent dams, and as a result of declining water quality (especially sediment, with organic and toxic pollution) • Blockage of key sections of the river for navigation – especially in the reaches between Vientiane and Chiang Saen 8.3.2 OPERATION IMPACTS As the hydropower schemes move into full operation, there are a number of changes that will affect the aquatic ecosystem, its productivity and biodiversity. These include: • Seasonal changes in flow: the dams have very little active storage capacity and they will tend to pass on the inflows coming through them. The total storage capacity of all twelve hydropower schemes is something over 2,553 mcm. The average yearly flow down the Mekong is 14,150 cu.m/sec. Thus the total active storage of the proposed mainstream dams would delay the flow into the Delta by about 2 days. In the dry season, when average flows are around 3,000 cu.m/sec at Kratie, the storage due to the mainstream dams might delay the first flushes of the river at the beginning of the wet season by up to 10 days. Of course there will be individual variations for the dams in different zones. The storage capacity of the Chinese dams and the large storage dams on the tributaries will have a much greater influence upon the seasonal flows. • From a landscape point of view, the reservoirs will appear throughout the year like the river at the height of the flood season, with the channel full. The seasonal variation in flow patterns will be reflected in terms of the flow velocity through the reservoirs, being much the same as at present in the wet season but much slower in the dry season. There is the same volume of water spread throughout the whole channel of the river, rather than being confined to the dry season channel. • Daily changes in flow: the operational rules for each of the dams is not yet clear; the decision to operate the dams in peaking mode rather than continuous generation will depend upon tariff agreements, and the environmental flow regimes required by the consenting agencies. A number of the dams will be operated as straight run‐of‐river dams, with little peaking, e.g. probably Pak Chom, Ban Koum and Latsua. In these cases the water levels in the reservoir will depend upon the flow, and 126 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS there will be little change in the downstream flows during the day. If the dams are operated in peaking mode, the downstream flows may be increased by several times the flow compared to the minimum flows released during non‐peak times. The level of the water in the reservoirs may change by as much as 2 m during the day for many of the dams and up to 5 m for dams such as Pak Beng, Xayaburi and Stung Treng. During the high flow season, this will be of relatively little consequence as the flows downstream will generally be much greater than the design flows; however, during the dry season, the downstream flows released will become critical for the aquatic habitats, and the differences in levels in the reservoir will become more pronounced. • Sediment movement and trapping: The predicted changes in passage of the sediment downstream as a result of trapping in Chinese and tributary dams shows that the sediment already in the system will continue to pass on downstream to the Delta, but will not be replaced to the same extent from sources upstream. Any changes due to the mainstream dams are superimposed upon the trapping of sediment that will take place in the Chinese mainstream dams and the storage dams on the tributaries. Run‐of‐river dams generally trap less sediment than storage dams; however, the trapping attributable to the mainstream dams may provide a “tipping point” of significant shift in the sediment dynamics of the Mekong. The changes in the hydrodynamics of the river caused by these mainstream dams will change the patterns of sediment movement and deposition, so that in general terms sediment will tend to build up at the head of the reservoirs in the dry season and be washed down into the main body of the reservoir with the flood waters. Deep pools at the top ends of the reservoirs may continue to operate as before, filling at the end of the wet season, and passing sediment on at the beginning of the dry season; however further down the reservoirs the deep pools will not flush out and will fill up with bedload and sediment. • Immediately downstream of the dams there will be a tendency to scour the bed, as the potential energy of the water released in power generation is localized. This scour may extend for several kilometers downstream as the channel realigns itself. In the longer term the deep pools downstream of the dams will continue to operate as they have, but with less sediment passing through them. • Hydrological changes over the next 20 years will have significant implications for the start and duration of the transition periods between dry and wet seasons, and between wet and dry seasons. In broad terms the Chinese dams and the storage dams on the tributaries will tend to delay the onset of the important ecological transition between dry and wet seasons, and will shorten this transition period, in some zones almost entirely (see explanation in the hydrological impacts paper). With the mainstream dams this trend is likely to be made more extreme. Vientiane at the end of Zone 2 may experience a delay in the onset of transition by up t a month, and the transition period be almost eliminated. The influence of the tributaries entering the river in Zones 3 and 4, means that the onset is less delayed by about 2 weeks and overall as it reaches the delta by 3 weeks. • The ecological implication of this delay in the onset of the transition from low to high flows is complex. In qualitative terms, the hydrological changes ‐ early peaks in flows, natural chemicals washed out of the soils, local rainfall ‐ often provide triggers for spawning of fish, for egg laying and hatching of eggs of amphibians and turtles. The close linkage between the timing of such events and availability of food, or the currents of the river carrying fish fry to the areas where they grow etc, is critical and if the timing is disturbed, breeding success may be very limited. If this goes on for a number of years it would lead to a crash in the populations of those affected species. • The timing of the onset of the wet to dry transition is also important, and whilst hydrological modeling does not show much change in the date of the end of the flood season (usually early November), the duration of the transition period together with the dry season shows significant extension for 20 year scenarios with and without the mainstream dams. Usually the effect of the mainstream dams would be 127 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS to extend this period from the end of the flood to end of dry season by up to 40 days in Zone 2, 18 ‐ 20 days in Zone 3, 4 and 5. During the transition period, as the waters recede, there is intense worm activity on the banks as they are exposed, breaking down vegetation and adding to the fertility of the river banks. The extended dry season, albeit with higher flows and water levels, will have ecological consequences that may change the balance of productivity and species diversity in the river. 128 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS Map 8.1: Even in narrow river valleys, there are seasonally exposed in channel wetland areas – Xayaburi dam site 129 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS Figure 8.1: Photo of Xayaburi Dam site. The water levels of the reservoir would be kept near this level. 8.3.3 IMPLICATIONS FOR THE AQUATIC ECOSYSTEM HABITAT CHANGE When the dams are finished and the reservoirs behind them are created, there would be a change in the aquatic habitats. In the areas inundated there would be losses of rapids and riffles and sandbars, and deep pools would tend to silt up. 996 km out of 2427 km of the Lower Mekong River (41% would be converted to run‐of‐river reservoir. 798 out of the 1100 areas of river over 10m deep would become part of reservoirs, with 38% of the areas occupied by pools of 10 – 20 m deep affected, 45% of areas occupied by pools 20 – 30 m deep affected and 59% of the areas occupied by pools over 30m deep. 93% of the area occupied by deep pools over 50 m deep will be affected by reservoirs. There would be an inundation of 76% of the total rock and rapids areas of the Mekong and 16% of the sand bars. These figures are summarized in the table below. In each of the zones the following changes are likely: ZONE 1: No change ZONE 2: Out of a total of 795 km of river, 694 km (87%) would be converted from a free flowing river to reservoir with some daily fluctuation in water levels. There will be the usual flows through these reservoirs, so there will be very little storage. This will mean that out of 460 sq km of the river channel, some 369 sq km (80%) would become part of the reservoirs. Of this about 50% is considered to be the dry season channel. Deep pools: 571 of the areas of river over 10 m deep will be affected, out of a total of 598 (95%). Most of these are between 10 and 20 m deep with a total area of 18.5 sq km out of 21.74 sq km (85%); 71% of the total area 130 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS of deep pools between 20 and 30 m deep and 25% of the pools deeper than 30 m will be affected by the reservoirs. Rocks and rapids: 151.6 sq km of rocks and rapids in this zone will be inundated by the reservoirs out of a total of 161.7 sq km (94%) Sand bars: 37.53 sq km of sand bars in this zone will be inundated by the reservoirs out of a total of 66.35 (57%) Figure 8.2: Photo of Pak Chom exposed river channel during recent low flows, showing diversity of wetland habitats 131 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS Map 8.2: Area around Pak Chom (Zone 2), showing the seasonally exposed in‐channel wetland areas, with the diversity of habitat. 132 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS Figure 8.3: Photo of Pak Chom area showing diversity of aquatic habitats at high flows ZONE 3: Out of a total of 713 km of river, 159 km (22%) would be converted from a free‐flowing river to reservoir in this zone. • Deep pools: 116 of the areas of river over 10 m deep will be affected, out of a total of 172 (67%). Most of these are between 10 and 20 m deep with a total area of 16 sq km out of 28.6 sq km (56%); 61% of the total area of deep pools between 20 and 30 m deep and 61% of the pools deeper than 30 m and 80% of the deep pools over 50 will be affected by the reservoirs. • Rocks and rapids: 42 sq km of rocks and rapids in this zone will be inundated by the reservoirs out of a total of 66 sq km (75%) • Sand bars: 1.17 sq km of sand bars in this zone will be inundated by the reservoirs out of a total of 55 sq km (57%) ZONE 4: Out of a total of 330 km of river in this zone, 143 km (43%) would be converted from free flowing river to reservoir. • Deep pools: 111 of the areas of river over 10 m deep will be affected, out of a total of 181 (61%). Most of these are between 10 and 20 m deep with a total area of 13.4 sq km out of 25.3 sq km (53%); 72% of the total area of deep pools between 20 and 30 m deep and 81% of the pools deeper than 30 m will be affected by the reservoirs. 100% of the areas of deep pools over 50m deep would be affected by the reservoirs. • Rocks and rapids: 3.1 sq km of rocks and rapids in this zone will be inundated by the reservoirs out of a total of 42 sq km (7%) 133 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS • Sand bars: 13 sq km of sand bars in this zone will be inundated by the reservoirs out of a total of 73 (18%) ZONE 5 AND ZONE 6: No change These changes in river morphology and habitat represent a very significant change in the landscape value and habitat diversity of the Lower Mekong. In Zone 2 this is taken to an extreme, where the cascade of dams from Pak Beng to Pak Chom will convert the river to a series of long thin reservoirs punctuated by a series of dams one leading into the next, with only a small piece of free‐flowing river between Louang Prabang dam site and the city, where the top of the Xayaburi reservoir starts. In this cascade the loss of particularly diverse habitats around Pak Chom and Sanakham may be very significant from an aquatic ecology point of view. In Zone 3, the extent of the reservoirs is not nearly so great, but the losses of deep pools and especially rocks and rapids is greater than might be expected, showing that Ban Koum reservoir especially actually inundates significant proportions of the important habitat diversity in this zone. In Zone 4, just under half the length of the river would be converted to reservoir, and a lot of the braided river channels and islands would be inundated. Whilst the rocks and rapids and sand bars are apparently less affected, there would be a considerable loss of the habitat diversity and landscape value, especially due to the Cambodian dams. CHANGES IN NET PRIMARY PRODUCTIVITY These changes in the river morphology and flow patterns will have an effect upon the primary productivity of the river. A first approximation of the order of magnitude of change in primary productivity as a result of the loss of seasonal exposure of in channel wetland areas has been made and is shown in Table 2. Whilst the actual amounts of NPP (net primary production) calculated in each zone should not be taken literally, the relative changes appear significant. For the whole of the mainstream of the Lower Mekong (excluding the Delta and Tonle Sap), the eleven mainstream reservoirs will cover about 38% of the length of the river (911 km) and reduce the area of river channel exposed during the dry season, which gives rise to varied in‐channel wetland habitats, by about 48%. This may depress the NPP of the whole river system of the Lower Mekong by a range of 12 – 27% depending upon the rate of primary production (0.6 – 1.4 Kg/m2/yr). When considering the separate zones, Zone 2, in which 77% of the length of the zone will be changed by the reservoirs, stands to lose about 82% of the seasonally exposed in‐channel wetlands, and may lose between 27 – 53% of its NPP. In this zone, Pak Chom reservoir contributes the greatest loss of seasonally exposed wetlands, about 26%, followed by Xayaburi which contributes some 20% to this loss of productivity. The other dams contributions to this loss range from 11% (Louang Prabang) to 15% (Sanakham). One direct use of primary production in this area is the collection of Mekong river weed, which forms an important livelihood opportunity for riparian communities. It is likely that under the new reservoir regime, the growth of this filamentous algae on the river bed in the dry season, would become very limited and could only be collected in some of the tributaries or above Chiang Khong/Houay Xai. Even in the areas downstream of the Louang Prabang dam to the headwaters of Xayaburi reservoir, the growth of the algae will be limited by the daily fluctuations in the water levels and rates of flow. In Zone 3, about 22% of the length will be changed by the reservoir, with about 42% of the seasonally exposed in‐channel wetland areas being lost, resulting in a loss in primary productivity of between 6 and 16%. Ban Koum in this zone stands out most significantly as contributing most of this loss of wetland area. In Zone 4, about 43% of the length of the zone will be affected by the reservoirs, with a loss of about 58% of the in‐channel wetland areas. This might cause a reduction in the primary productivity of the area of between 134 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS 15 and 32%. The two Cambodian dams are most significant in their contribution to these reductions, with Sambor almost double the impact of Stung Treng. 135 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS Map 8.3: Ban Koum dam site and reservoir, showing diversity of river channel and aquatic habitats, including seasonally exposed river channels 136 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS Figure 8.4: Mekong river weed at risk? Louang Prabang morning market Figure 8.5: Photo of the river near Ban Koum dam site (from Pha Taem National Park), showing seasonally exposed rocks and rapids. 137 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS Map 8.4: The Don Sahong dam occupies a small area of Siphandone but would block a strategically important fish migration route 138 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS Figure 8.6: Fish traps on the Hou Sahong Figure 8.7: flooded forests in the Stung Treng Ramsar site would be permanently flooded 139 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS Map 8.5: Mekong River channel between Khone Falls and Stung Treng, showing area of inundation of proposed Stung Treng dam 140 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS Figure 8.8: A threatened species? Tourists watching dolphins near Kratie, Cambodia Zones 5 and 6 will be unaffected by these changes, since the in‐channel wetland areas will continue to be seasonally exposed as before. Whilst a mathematical relationship between primary productivity and fish production would be very complicated to determine, there is a direct linkage through the food chain. It is reasonable to project that fish yields in each of the affected zones might change by similar proportions, although there will be an additional contribution to productivity from the inundation outside the mainstream channel, which has not be included in these estimates. In general, it is predicted that the productivity of the mainstream reservoirs from this source of in‐channel wetlands could be reduced by between 30 and 60% compared to their current productivity. CHANGES IN AQUATIC BIODIVERSITY The changes in aquatic biodiversity as a result of these dams stem from several different factors: • Changing habitat diversity with the river in the reservoirs upstream of the dams losing much of the diversity as shown above. In particular, the diversity of rapids, riffles and sand bars will be completely lost in the reservoirs, and deep pools will either tend to be filled in or become less dynamic. • Changing habitat diversity downstream of the dams as a result of variable and unpredictable flow patterns, and extremes. The trapping of sediment in both the upstream dams and the mainstream dams will tend to reduce the passage of sediment and sandbars downstream overtime, although deep pools may still provide a dry season refuge. • Loss of key spawning and feeding areas within the Mekong mainstream, especially the riffles and sandbars and the in‐channel wetlands, both as a result of inundation, and changing flow patterns downstream of dams 141 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS • Barriers to fish movement and migration45 and isolation of sections of the river from each other and from major tributaries. These barriers are accentuated in cascades, even if the dams are fitted with effective fish passages. In a cascade, each reservoir is effectively a separate unit, especially when there are no major tributaries entering the mainstream in between the head waters of the reservoir and the dam. • In general reservoirs tend to be less biodiverse than rivers, often a reflection of the habitat diversity. For example, in Nam Ngum the reservoir fisheries catch about 20% less species than riverine fisheries in the Nam Ngum basin (Vattenfall, 2009) • Construction activities that change sediments, water quality and flows such as to drive fish away, smother important downstream habitats, or cause mortality of aquatic organisms. It has been indicated in the Nam Ngum river basin monitoring that dam construction activities can depress fish catches by up to 50% and cause localized losses of up to 30% of fish species within 20 – 50 km downstream of the dam. (Vattenfall, 2009) IMPLICATIONS FOR AQUATIC BIODIVERSITY OF THE MEKONG • Overall – In general the construction of dams, the reduction in the diversity of aquatic habitats by the inundation of the reservoirs, and the changing flow patterns will tend to reduce the overall biodiversity of the Mekong. The breaking up of the river into isolated segments will isolate populations, which may no longer be viable, leading to losses of some species. This will be reflected most obviously in the fish species, which may be reduced by up to half of the recorded species in some zones. This may also be measured in mollusk species diversity – the Mekong has the highest number of freshwater snails in the world – and other invertebrates that make use of the different aquatic habitats available. Amphibians depend upon the wetland pools left by the receding waters for breeding ‐ the importance of the in‐ channel seasonally exposed wetlands for both habitat and species diversity and productivity can not be over‐emphasised. More specifically for each zone: • Zone 1: will be affected by the changing flow and sediment patterns from the Chinese dams, and the isolation from the rest of the Lower Mekong. It will no longer receive the long distance migrations of fish such as Pangasius krempfi and Anguilla marmoratus. • Zone 2: will be one of the most affected zones in terms of biodiversity. The mainstream dams will cut the zone up into isolated segments, and since there is no major tributary entering the Mekong in these segments (apart from the Nam Ou, the Nam Xuang and the Nam Kham between Louangprabang dam and Xayaburi dam), most of these segments will become increasingly species impoverished, since spawning grounds will be inundated or inaccessible. The major in‐channel wetlands in the Pak Chom area, extending up past Sanakham and Pak Beng, are considered to be important breeding areas and refuges for many species, representing important transition between the species in the Upper Mekong and the Middle Mekong. If this is lost, then species richness will be lost in both Zones 2 and 3. • Zone 3: although this zone has only two dams, one of them Ban Koum is located at an area of high habitat diversity, especially for rocks and rapids and deep pools, in an otherwise rather simpler aquatic zone. Ban Koum reservoir could have an impact upon the species diversity of the zone, though not enough is known about the fish species there. 45 Detailed consideration of fish migration is provided in the fisheries theme. 142 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS • Zone 4: with its varied habitat diversity, this zone has arguably the richest biodiversity of the Mekong mainstream. Upper part of Siphandone may be adversely affected by the flows from Latsua, although since this appears to be operated as one of the true run‐of‐river dams, this may not be so damaging. Despite damming only a relatively small channel of the Mekong beside Khone Falls, the key issue facing Don Sahong dam is fish migration. The dam would block the only channel that is used by fish for migration throughout the year at all water levels. Blockage of this channel could seriously impair the diversity of the fish species and their productivity on both sides of the Khone Falls. The two Cambodian dams would flood more extensive areas than the other dams and would reduce the diversity of habitats considerably, probably with the loss of many fish, reptile and mammal species. Even if fitted with fish passages, they would likely prevent the large fish migrations that currently characterize the zone. • Zone 5 and 6: do not have dams planned and so will not involve major changes of habitat. The main impacts will be upon the reduced access of upstream areas for fish migrations by Sambor dam. This may eventually lead to significant declines in migratory species in the Tonle Sap and in the Delta, if these species are no longer able to reach alternative spawning sites and growing areas. CHARISMATIC AND ENDANGERED SPECIES • Irrawaddy dolphin – this critically endangered species, living in Zone 4, below the Khone Falls down to Kratie, would be further threatened by the construction and operation of the mainstream dams in the Zone, and this might be the final threat which drives the extinction of this sub‐population. Construction impacts in zone would cause massive disturbance to these sensitive animals. The Don Sahong dam lies immediately above the small group living in the deep pool shared by Lao and Cambodia and construction activities would almost certainly drive them away. The other groups living in deep pools between the Khone Falls and Kratie, would be disturbed, and would eventually be separated from each other by the Stung Treng Dam. They would also suffer from changes in availability of fish as their main food source. However, it should be noted that the Indus Dolphin populations do survive and appear to thrive in groups separated by the barrage headponds on the river Indus, but these structures were built many years ago when the dolphin populations in the Indus were greater. The possibilities of Irrawaddy Dolphin surviving in hydroelectric dam reservoirs would need to be thoroughly studied. • Giant Mekong Catfish is known to migrate out of the Tonle Sap and into the Mekong mainstream for spawning. A few individuals have been caught in recent years moving up past Khone Falls, i.e. through Zone 4 and into Zone 3. The other known area where they are caught is near Chiang Khong/Houay Xay at the top end of Zone 2 and it is presumed that spawning takes place nearby. The mainstream dams would prevent the long distance migration of the Giant Mekong catfish through Zones 5, 4 and 3, and this would probably lead to its extinction form the Tonle Sap, because it would be unable to reach its spawning grounds. If the fish caught near Chiang Khong are a separate sub‐population migrating in the Upper Mekong, it is possible that these fish could survive in Zones 1 and 2, but if they are all part of the same population depending upon their migration through the length of the Mekong, then they would become extinct in the wild as a direct result of the mainstream dams. • Siamese crocodile: the only remaining location on the Mekong mainstream where Siamese crocodiles may exist is in small tributaries within the Stung Treng Ramsar site. The construction and inundation of the Stung Treng dam would certainly lead to the local extirpation of these small populations. Other wild populations exist in the Cardamom mountains of Cambodia, which would not be threatened by the mainstream dams. 143 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS • Turtles are generally found throughout the Mekong, although increasingly rare and threatened by hunting. The mainstream in Zone 4 (in Cambodia) is seen as globally significant for Cantor’s giant soft‐ shell turtle and may support the largest remaining breeding populations in the basin. All turtles are threatened by loss of their breeding habitat, the sandbars exposed during the dry season. As has been shown above many of the sandbars will be lost, submerged within the reservoirs, or reduced over time as larger proportions of the sediment load is trapped behind Chinese, tributary and mainstream dams. The mainstream dams would certainly contribute significantly to significant reductions in populations of most of the turtle species living in the Mekong. • Otters – the three species of special interest in the Mekong basin – the hairy‐nosed otter (endangered), the smooth coated otter and the oriental small‐clawed otter (both vulnerable) – have been found in the Tonle Sap system and in the stretches between Kratie and Siphandone, Zone 4. They may also be found higher up in the river, certainly in areas where there are diverse aquatic habitats that provide shelter, suitable breeding places and food sources. The effect of the dams and reservoirs to limit this diversity and reduce the availability of suitable habitats would be an additional threat to these and other otter species. CHANGES IN WATER QUALITY The general impacts of these run‐of‐river mainstream dams on water quality comes mainly during the construction phase. There are three types of water quality issues associated with any large infrastructure development in or around water courses: • Increase in sediment as a result of rock blasting and earthmoving. It is impossible to predict how much the sediment load in the Mekong will be increased as a result of construction, but it could be locally very significant at certain times during construction, especially if this coincides with low water flows, at times when the lowest sediment loads are being carried. The significance of increased sediment released downstream is that it may deposit on and smother gravel beds and riffles downstream that are important for fish spawning. • Increase in organic matter as a result of uncontrolled discharge of waste waters and solid wastes from construction camps. Again largely a localized issue given the high dilution usually afforded by the Mekong waters, but this may become significant at times of low flow. This should be controlled by adequate waste water treatment and solid waste water disposal by the contractors. • There is usually an increase in organic matter and increase in the oxygen demand of the water during the initial impoundment, as the remaining vegetation in the reservoir area breaks down. This is likely to be limited in the case of these mainstream dams since they are generally confined to the existing river channel, with small landward inundation. The only exception to this would be the Cambodian dams which would flood islands and larger areas of land that may need prior clearance before inundation. • Accidental spillage of construction materials, concrete, toxic compounds and fuel and oils. Discharge of used engine oils from construction vehicle maintenance into water courses is a common occurrence. The risks of this would be substantially increased by the concentration of construction work of these dams over the next 15 years. In terms of operation, these mainstream dams are not expected to have a significant impact upon water quality. There is comparatively little storage, either dead or active storage and little opportunity for the accumulation of anoxic waters, which cause problems downstream when released. Similarly, unlike storage 144 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS dams which can release significantly colder waters downstream, these dams will draw turbine waters from the upper layers of the reservoir, which should be fully oxygenated. The details of sediment flushing operations have not been developed at this stage, the MRC Technical Design Guidance for Mekong Mainstream Dams (MRC 2009) indicates that during flushing or sluicing operations, the reservoir is drawn down and behaves like a normal river reach transporting accumulated sediments through the dam. This results in concentrated sediment discharges, i.e. water with high sediment loads than normal (typically exceeding 100g/l commonly as much as 1000g/l), which can adversely affect water quality, particularly when done at sensitive times of year, e.g. during low flows. The MRC water quality parameters and thresholds indicate that a Total Suspended Solids concentration of more than 50 mg/l in the river water is considered “Very Bad”, although naturally high and increasing TSS concentrations are observed between upstream stations and Vientiane, where they can reach an average of 400mg/l. (MRC, 2007). The flushing releases from dams are significantly higher than this, and so need careful management not to impair the operation of downstream dams in a cascade, nor the remaining riverine ecosystem downstream of others. One other aspect of solids transport down a river system, that is often overlooked, is the floating matter – logs, bamboos, plastic bags, dead animals etc. When operating with the spillway gates open, these items should pass through the dams and on downstream as usual, but when just passing water through the turbines, these will be collected on grills and removed. At lower flow situations floating items will be taken out of the system. This is a dam management issue that needs appropriate coordination between the dams and operation that follows accepted standards. Figure 8.9: Timber industries along the Mekong near Sanakham – a cause of pollution? (this could go in aquatic impacts 145 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS Fig 8.10: Logs floating downstream are a management issue for dams CHANGES IN THE CULTURAL ECOSYSTEM SERVICES As described in baseline section the cultural ecosystem values of the Mekong river can be divided into cultural and inspirational values, key festivals, recreational and Mekong tourism features. These are largely associated with its aesthetic and landscape value and strong associations with seasonal variation. On the spiritual and inspirational aspects, important “naga” myths are often linked to specific locations in the river such as deep pools and rapids, places where the landscape value is also high. As can be seen from the descriptions of the changes in aquatic habitats and landscape value due to the dams, such places are likely to experience changes, many of them becoming part of reservoirs and tending to lose their unique character. The fireball festival near the confluence with the Nam Ngum river on both Lao and Thai banks is associated with naga myths and may be affected by the changes in the seasonal flow patterns. If the dams are built and reservoirs created, this will result over time in a decline in the strength of the naga myths in these areas. Festivals such as the Giant Mekong catfish festival in Chiang Khong are clearly dependent upon the presence of the endangered fish. If the dams act as a barrier to exclude the migrating fish from the area or lead (along with other threats such as changing habitat and overfishing) to their extinction, then this festival will lose its original purpose. Boat racing festivals all along the Mekong celebrate the end of the flood season, or in the case of Phnom Penh, the change back to normal of the flows in the Tonle Sap river. If these mainstream dams are built, those towns and villages living along the banks of one of the new reservoirs will experience little seasonal change in height of the waters, although the flow rates will still change significantly. 146 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS Figure 8.11: Celebrating the start of the Giant catfish fishing at Chiang Khong (Source: Zeb Hogan) The recreational value of the river depends highly upon its aesthetic and landscape value, often for eating and relaxing along the banks. During the low flow season the river channel itself, the banks, sandbars and exposed rocks are used for picnicking, swimming, walking, angling, playing football etc. One of the implications of lower sediment flows coupled with higher dry season flow levels, is that exposed sandbars, such as those around Vientiane, may be much smaller in the future, offering less free recreational space and reducing its value. The mainstream dams will contribute to a small extent in this decline. The most economically realizable cultural value of the river is through Mekong tourism, the economic value of which is very big. As shown in the baseline each zone has a number of unique features – natural e.g. the Irrawaddy dolphin and landscape features such as the Khone Falls, and tourists are currently attracted to the river because of its reputation as a “wild” river, passing through magnificent landscapes. The construction of the mainstream dams will have an undoubtedly impact upon this attractiveness, and over the next 10 years the boat tourism between Louangprabang and Chiang Khong will probably be lost almost entirely. Even when the dams are operating in Zone 2, and tour boats can pass though the navigation locks, the tourism experience will be very different. Whilst the boat tourism in Siphandone will be largely untouched, the developments at Don Sahong and especially the channel of the Thakho hydropower scheme around Khone Falls will have an impact upon the tourism experience there and will reduce the natural grandeur of the Falls. The disappearance of the Irrawaddy Dolphins would be a significant loss from the Cambodian and Lao tourism attractions, although the declining populations can not yet be attributed to the mainstream dams. The decision to start building the mainstream dams may be associated with an immediate boom in “last chance to see” type tourism on the Mekong, which would then be followed by at least a decade of disruption as the different dams are built. Once built and operating, perceptions and tours will adapt to take advantage of 147 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS the changed conditions of the dams, locks and reservoirs. Dams are noted tourism attractions in their own right, and the terrestrial landscape and culture of the Mekong countries will continue to attract. Figure 8.12: Tourism river traffic between Louangprabang and Chiang Khong/Houayxai would be disrupted during the dam construction phase 8.4 SENSITIVITY ANALYSIS OF DAM GROUPINGS In undertaking this sensitivity analysis, two questions are considered: • What will be the critical changes arising from the group of dams in their own location compared to the overall Mekong aquatic ecosystem? • What will be the critical changes arising from the group of dams on other parts of the Mekong aquatic ecosystem? 8.4.1 CASCADE OF 6 DAMS UPSTREAM OF VIENTIANE If the upper cascade of six dams were installed but none of the other dams, the changes to the aquatic ecosystems of Zone 2 would be very significant, as has been shown above. Over 80% of the zone would be changed from a free flowing river to a regulated set of reservoirs that run into each other. Similar proportions of all the aquatic habitats (rocks and rapids, riffles, sand bars and deep pools) would be changed, with a consequent loss of breeding and spawning areas. The aquatic biodiversity of this zone would become seriously impoverished, the more so because there are few major tributaries entering the zone, which can provide alternative spawning areas. Productivity of this zone would also decrease, especially for Mekong river weed. The loss of critical diverse aquatic habitats above Vientiane, e.g. Pak Chom, which probably mark a transition point between the upper river and the middle reaches, represents a loss of a unique area in the Mekong, 148 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS possibly comparable in importance, though not in scale, to aquatic ecology as some of the other areas of aquatic habitat diversity lower down the system, e.g. in Siphandone. In terms of the influence that these dams have on other zones, there will be an immediate downstream impact zone, extending at least down to Vientiane as a result of daily variations in flow, and sediment trapping and flushing discharges. However, these will certainly have been balanced out by the time the river has passed through the rest of Zone 3. The biggest impact from an aquatic ecology point of view will be as a barrier to migration of fish. The lower part of Zone 2 acts as a transition between the upper reaches and middle reaches of the Lower Mekong and hence indirectly with the lower reaches, the delta and the sea. The biggest loss would therefore be upon connectivity between the sea and the Upper Mekong. Even if all the dams in the cascade are fitted with efficient and effective fish passages, the stretch of six dams in cascade over a distance of nearly 800 km represents an impossible barrier for the long distance migratory species. 8.4.2 MIDDLE MEKONG DAMS The two dams in the middle reaches of the Mekong, Ban Koum, shared between Thailand and Laos, and Latsua which lies completely in Laos, will have less an effect upon Zone 3 itself than the cascade above Vientiane has upon Zone 2. However, Ban Koum does occupy a stretch of the river which is distinct and ecologically significant in the context of Zone 3, with almost all the deep pools and rocky/rapid areas in the Zone. These two dams are intended to operate as near to run‐of river as possible with minimum daily draw down, and so should have little impact downstream in terms of daily flow variation. However the influence of Ban Koum will be felt in the aquatic ecology as far downstream as Pakse, and the influence of Latsua will be felt well down into Siphandone, but probably not beyond Khone Falls. As before these two dams will act as a significant break in the connectivity of the mainstream between the lower parts of the Mekong and the middle and upper reaches. If these two dams were constructed with effective fish passage for both upstream and downstream migrations, this might be less important, but current designs of fish passage are unlikely to be effective for more than a few species. The relevance of fish passage in this section is not just relevant for the fishery in the mainstream, but also for the tributaries in southern and central Laos. It is likely that the fish productivity and biodiversity would be lost from these tributaries as a result of these two middle reach dams. 8.4.3 LOWER MEKONG DAMS The significance of the dams in the lower Mekong, in Cambodia is that they would inundate one of the richest and most biodiverse areas of the entire Mekong system, an area which is of global importance to aquatic biodiversity. This is a unique area with immense diversity of river morphology, aquatic habitats and landscape value, both in the Mekong system, but also in other major river systems. Because of the topography and nature of the river channel, the area of inundation would be much larger than the dams upstream, and cover many of the islands, deep pools, rocks and rapids and sandbars. They would almost certainly involve the loss of rare and endangered fish species, and most probably be the final threat for the Irrawaddy Dolphin. The area is an important spawning and breeding ground for many species, and it is not clear if alternative breeding grounds would still be available. If these lower Mekong dams were to be constructed by themselves, the biggest impact to the system would be in terms of the connectivity of the system, especially for fish migration. The Mekong above Kratie to the Laos border and up the Khone Falls is an important destination for fish migrating out of the Tonle Sap. The combination of Sambor and Stung Treng dams would effectively stop this. Sambor dam would also stop the important fish migration route up the 3S rivers, especially the Sekong. The downstream flows from Stung Treng dam might also alter the fishes ability to navigate up the 3S rivers. 149 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS The smaller hydropower schemes at Khone Falls – Don Sahong and Thakho – are of significance here for different reasons. Thakho HPP is true run‐of‐river involving a diversion or a proportion of water around the Khone Falls. It will have no effect upon fish migration. Don Sahong would effectively block the only channel that is known to provide a year‐round route for migrating fish. Unless alternative and effective routes for fish passage are provided, this would be a barrier for some of the important small commercial species that use it during the dry season. However, the barrier effect of Don Sahong would probably become almost irrelevant if Sambor and Stung Treng dams are built. Downstream of Sambor, the aquatic ecology of the river below Kratie would be affected by changing daily flow patterns and sediment trapping and flushing. It is probable that the reservoirs in Sambor and Stung Treng would allow more sediment to drop out than the narrow in‐channel upstream dams, so there are likely to be losses of sediment to the river downstream, that will not be rectified by sediment flushing. 8.4.4 POSSIBLE INDIRECT LINKS WITH OTHER FUTURE TRENDS As can be seen from the discussion above, the aquatic ecosystem theme is highly dependent upon the changes predicted by the hydrology and sediments theme. River morphology and aquatic habitat diversity result from the interaction between flows of water and sediments and the underlying geology of the basin. There would be link between these aspects through the river morphology to navigation. Navigation will be enhanced by the higher water levels of the reservoirs, and passage through the dams facilitated by navigation locks. However, there will be section of the river immediately downstream of the dams that may prove more difficult for navigation of larger boats, since the water levels may vary on a daily basis depending upon the mode of operation. The difficulties of maintaining navigation in the reach between Vientiane and Chiang Saen during the construction period of the cascade of dams has already been mentioned. For smaller fishing boats, the rapid change in flows resulting from peaking operations and sediment flushing, can be a significant safety issue, that can only be minimised by excellent communications of such operations to local river users. The change in the primary productivity of the aquatic ecosystems of the river will have implications for the overall productivity of the river in general and in the reservoirs themselves. It is unlikely that they will be as productive in terms of the fishery as Nam Ngum, which depends largely upon the nutrient inputs from a number of different tributary rivers. The cascade dams above Vientiane in particular have very few tributaries and are a very different type of reservoir. This has implications for fish catches and the livelihoods of the riparian communities. The decline in Mekong River weed in the mainstream of zone 2 will also have serious implications for the supply of this product and another source of riparian livelihood. During construction, water quality issues and risks have implications for river users and sources of drinking water, i.e. affecting public health of riparian communities. During operation, these risks should be less, except during periods of sediment flushing, when drinking water sources will be put at risk by the high sediment concentrations. The changes to cultural ecosystem values of the river will affect the social, cultural and religious structure of communities along the river, especially those adjacent to the reservoirs or immediately downstream of the dams. The perception and willingness to pay for river based activities of visitors and tourists to the Mekong region will be affected, especially during the construction period, and tourism products and marketing will have to be changed once the dams and reservoirs have been created to re‐develop river based tourism. This has both important livelihood and economic implications. 150 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS Table 8.1: Profile of the Mekong River Channel in the different zones, featuring the areas occupied by the proposed mainstream dams Average Length of width of No of deep Habitat features Ecological Zone Characteristic Dams Riverriver Area of channel pools Area of deep pools (Area > 10 m Rocks Plain Dry deep in dry >=10 m >=20 m >=30 m >= 50 m and Sand section section season Wet season season depth depth depth depth Rapids bars km m sq km sq km sq km sq km sq km sq km sq km sq km China to Chiang Headwaters and 2,120 Saen mountain river Chinese dams 795 914.64 238.37 459.73 598 21.74 3.35 0.17 0.00 161.74 66.35 Pak Beng 160 500.00 43.72 67.36 98 1.47 0.02 0.00 0.00 14.28 9.35 Louangprabang 147 400.00 25.46 46.21 146 3.86 0.36 0.01 0.00 19.84 0.91 Xayaburi 95 500.00 30.11 67.17 96 3.38 0.55 0.00 0.00 31.11 6.14 Chiang Saen to Upland river in steep Pak Lay 110 510.00 23.43 49.93 112 3.51 0.52 0.01 0.00 26.32 0.19 Vientiane narrow valley Sanakham 97 695.00 38.99 66.82 67 2.47 0.13 0.00 0.00 26.15 8.22 Pak Chom 85 900.00 24.56 71.17 52 3.81 0.80 0.01 0.00 33.90 12.72 TOTAL Zone 2 dams 694 186.27 368.66 571 18.50 2.38 0.04 0.00 151.60 37.53 % of Zone 2 87 78 80 95 85 71 25 0 94 57 713 950.00 575.67 696.98 172 28.56 8.45 2.16 0.19 66.25 55.26 Ban Koum 149 950.00 71.73 121.67 110 13.35 4.66 1.19 0.15 49.64 0.30 Thai/Lao midstream Vientiane to Pakse Latsua 10 800.00 8.14 9.07 6 2.68 0.47 0.13 0.00 0.06 0.87 and tributaries TOTAL Zone 3 dams 159 79.87 130.74 116.00 16.03 5.12 1.32 0.15 49.70 1.17 % of Zone 3 22 14 19 67 56 61 61 80 75 2 330 1,500.00 529.98 805.77 181 25.34 4.44 1.41 0.36 41.75 72.74 Wetlands of Don Sahong 5 150.00 0.81 0.63 0 0.00 0.00 0.00 0.00 0.18 0.00 Siphandone, Khone Thakho N/A Pakse to Kratie Falls, Stung Treng and Stung Treng 52 1,800.00 39.35 104.82 64 4.44 1.15 0.39 0.02 2.88 0.74 Kratie, including Sambor 86 2,200.00 159.02 253.94 47 8.98 2.02 0.75 0.34 0.00 12.32 significant tributaries TOTAL Zone 4 dams 143 199.17 359.39 111 13.42 3.18 1.13 0.36 3.06 13.06 % of Zone 4 43 38 45 61 53 72 81 100 7 18 Kratie to Phnom Penh and Tonle Floodplains and the Sap Great Lake 364 1,100.00 413.32 550.09 121 51.89 7.47 0.54 0.00 0.00 136.77 Phnom Penh to Mekong Delta, Tidal the sea zone 225 28 Lower Mekong Total Lower Mekong 2427 1757 2513 1100.00 127.53 23.71 4.27 0.56 269.75 331.11 River Total in reservoirs 996 465 859 798.00 47.96 10.68 2.50 0.52 204.36 51.75 % 41 263473384559937616 151 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS Table 8.2: Potential Changes in primary productivity in the zones due to impoundment Length of Characteristic River Channel Areas Primary productivity - NPP area Total NPP of Total NPP of exposed in due to dry due to wet due to area due to area zone @ lower zone @ higher Wet dry season season season exposed in exposed in dry rate for rate for Dry season season (lost when channel - 0.3 channel - 0.3 dry season - season - 1.4 exposed exposed section channel channel inundated) KgC/m2/yr KgC/m2/yr 0.6 KgC/m2/yr KgC/m2/yr areas areas km sq km sq km sq km TonsC/Yr TonsC/Yr TonsC/Yr TonsC/Yr TonsC/Yr TonsC/Yr Headwaters and 2125 mountain river Chinese dams Total Zone 2 795 238.37 459.73 221.35 71,512 137,918 132,810 309,891 204,323 381,403 TOTAL Zone 2 dams 609 186.27 368.66 182.39 Upland river in Area remaining free flowing 52.11 91.07 38.96 15,632 27,320 23,376 54,544 39,008 70,176 steep narrow Area inundated 0.00 368.66 0.00 0 110,598 0 0 110,598 110,598 valley Total NPP in zone with dams 149,606 180,774 Difference due to impoundment 54,717 200,629 % change due to impoundment 77 78 80 82 27 53 Total Zone 3 713 575.67 696.98 121.31 172,702 209,094 72,784 169,828 245,486 342,531 TOTAL Zone 3 dams 159 79.87 130.74 50.87 Thai/Lao Area remaining free flowing 495.80 566.24 70.44 148,740 169,872 42,263 98,615 191,003 247,355 midstream and Area inundated 0.00 130.74 0.00 0 39,222 0 0 39,222 39,222 tributaries Total NPP in zone with dams 230,226 286,577 Difference due to impoundment 15,260 55,954 % change due to impoundment 22 14 19 42 616 Wetlands of Total zone 4 330 529.98 805.77 275.78 158,995 241,730 165,470 386,098 324,465 545,093 Siphandone, TOTAL Zone 4 dams 143 199.17 359.39 160.22 Khone Falls, Area remaining free flowing 330.81 446.38 115.57 99,243 133,913 69,340 161,794 168,583 261,036 Stung Treng and Area inundated 0.00 359.39 0.00 0 107,817 0 0 107,817 107,817 Kratie, including Total NPP in zone with dams 276,400 368,854 significant Difference due to impoundment 48,065 176,239 tributaries % change due to impoundment 43 38 45 58 15 32 Floodplains (figures exclude the Great Lake) No impoundment 364 413.32 550.09 136.77 123,996 165,026 82,060 191,474 206,056 315,470 Mekong Delta, Tidal zone No impoundment 225 Total Lower Mekong 2427 1,757 2,513 755 527,205 753,767 453,124 1,057,290 980,330 1,584,496 Total with impoundment 911 1292 1654 393 862,288 1,151,674 Difference due to impoundment 465 859 362 118,042 432,821 % change due to impoundment 38 26 34 48 12 27 152 ICEM – International Centre for Environmental Management 9 FISHERIES 9.1 STRATEGIC ISSUES • Long distance migration barrier effects, • loss of fisheries production and • loss of species This analysis will focus on the consequences of mainstream dams for fish production in the Mekong Basin. In order to detail impacts on a local level, dam projects will first be clustered in relation to the three main fish migration zones. For each zone, predicted hydrological conditions with and without Lower Mekong mainstream dams will be then reviewed, and the changes in flooded area will be specified. Since dam development will not have the same impact on long distance migrants (white fish) and on local residents (black fish), species composition basin wide will be reviewed and the proportion of species at risk will be characterized. Dam development also presents opportunities for reservoir fisheries and increased aquaculture production. This report will quantify the potential production gains from dam reservoirs. For each cluster of dams, this analysis will review: i) changes in hydrology, flooded area and aquatic habitats; ii) impacts of these changes on biodiversity; iii) impacts of these changes on local production (loss of species, loss of capture fish production), and iv) gains in reservoir production (reservoir fisheries and aquaculture production). Capture fish production losses in presence of dams will be compared to possible losses in absence of dams, and will be combined with expected reservoir fish production in order to provide a net estimate of changes in fish production by cluster and by zone. Mitigation measures aimed at facilitating migrations through dams and minimizing capture production losses will also be reviewed. The overall performance in the case of Mekong mainstream dams will be assessed. Ultimately, this report summarizes predicted trends in fisheries resources, with and without mainstream dams, in 10 and 30 years from now. 9.2 THEMATIC OVERVIEW An update about the relative share of black fish and white fish basin wide led to the conclusion that between 35% and 70% of the fish caught basin wide are long‐distance migratory species vulnerable to mainstream dam development. The current level of knowledge does not allow a lower uncertainty range. Losses in capture fish production will be high even in absence of mainstream dams. The presence of 77 tributary dams in the basin by 2030 will result in obstruction of 37% of fish migration routes and loss of at least 250,000 ha of floodplains. However losses in fish production in absence of mainstream dams cannot be precisely quantified. Total fish production at risk from mainstream dam development ranges between 700,000 tonnes and 1.4 million tonnes per year (170,000 – 340,000 tonnes for Cambodia, 60,000 – 120,000 tonnes for Laos, 250,000 – 500,000 tonnes for Thailand and 240,000 – 480,000 tonnes for Vietnam). This estimate converges with the estimate resulting from the expert consultation organised by the MRC in 2008 (700,000 – 1.6 million tonnes). The lower range of the latter two estimates also converges with that of the BDP2 study of impacts on fisheries, i.e. 600,000 153 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS tonnes. So the most conservative figure agreed by all studies and experts, i.e. 600,000 tonnes of fish possibly lost, is equal to the annual inland fish production of all of West Africa. In other words, all experts and studies agree that building 11 mainstream hydropower dams implies an ecological and food security risk equivalent to depriving 15 west‐African countries of all their freshwater fish. The production of reservoir fish could partly compensate for these losses. For mainstream dams, the reservoir surface area alone is the best single predictor of productivity. Productivity ranges from 20 kg/ha/year to 200 kg/ha/year, the variability being partly explained by factors such as depth of the reservoir or connection with rivers upstream. This large range illustrates the largely unpredictable nature of reservoir fish production. An analysis of surface areas of reservoirs created by mainstream dams (1500 km2) and of productivity leads to the conclusion that the highest fish production that can be expected from fisheries in mainstream Mekong reservoirs would be 30,000 tonnes. In fact the most likely production represents about 10,000 tonnes. The total amount of reservoir fish produced in all reservoirs of the LMB (mainstream + tributaries dams) would range between 25,000 and 250,000 tonnes, the most likely scenario being 63,000 tonnes. However this additional fish production is very small compared to predicted losses in capture fish production resulting from the obstruction of migration routes and changes in hydrology and habitats induced by hydropower dams. Overall the study also concludes that dams located upstream of Vientiane would have less impact on fishery resources than those located further downstream. The dams having by far greatest impact on fish resources would be Latsua, Stung Treng and in particular Sambor, because they would block the migration route of most species. The BDP2 has issued on 11th May 2010 a draft independent report on impacts of mainstream dams on fisheries resources. The findings of this report, briefly reviewed, are in line with the findings of the current assessment. Assessments of impacts of dams on biodiversity are more detailed in the SEA Fisheries report, whereas impacts of dams on capture fisheries and aquaculture production are more detailed in the BDP2 report. Possible losses in capture fish production, detailed in the present report, range between 700,000 and 1,400,000 tonnes. In 2008 panel of experts also estimated the possible losses at 700,000 – 1,600,000 tonnes (Barlow et al. 2008). The possible losses quantified in the BDP2 report amount to 600,000 tonnes. Whatever the discussion about the range of possible losses, it should be noted that the most conservative figure agreed on by all studies and experts, i.e. 600,000 tonnes of fish possibly lost, represents the annual inland fish production of the whole West Africa.46 In other words, all experts and studies agree that building 11 mainstream hydropower dams implies an ecological and food security risk equivalent to depriving 15 west‐African countries of all their freshwater fish. The present study and the BDP2 fisheries studies are also in agreement about the low fish production to be expected from reservoirs. The SEA study amounts this production to 25,000 ‐ 250,000 tonnes, the most likely scenario being 63,000 tonnes, whereas the BDP2 study amounts this production to 16,000 – 64,000 tonnes. Several aspects in fisheries have not been covered by the current study nor by BDP2 study; these are: • the impact of sediment retention by dams on water productivity and fish production; • the changes in quality of fisheries products in the case of change in species composition, in particular the nutritional value of the newly dominant species and the possible impact of human diseases such as liver fluke present in multiple small cyprinids; • the changing value of fisheries products, depending on changes in catch composition and on market demand for a scarcer product; • the socio‐economic issues and shifts of benefits between social groups following losses and changes in species composition. Ultimately, it should be kept in mind that both SEA and BDP2 studies are initial attempts to assess the impact of investments worth USD 18,847 million on a resource worth USD 2,100 – 3,800 million. The magnitude of possible 46 Benin + Burkina Faso + Chad + Côte d'Ivoire + Gambia + Ghana + Guinea + Guinea Bissau + Liberia + Mali + Niger + Nigeria + Senegal + Sierra Leone + Togo; FAO statistics 154 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS impacts definitely calls for major investment in additional in‐depth assessments of impacts of hydropower development on food security in the Mekong Basin. 9.2.1 SENSITIVTY ANALYSIS OVERVIEW For fisheries impacts, 3 clusters of dams have been examined: upstream cluster between Chiang Saen and Vientiane, middle cluster between Vientiane and Pakse, and downstream cluster between Pakse and Kratie. Table 9.1: Fisheries opportunities and risks for 3 key clusters of LMB mainstream projects Components of Likely expected opportunities or risks caused by this component the HP plan (1) Upstream • 262 species (22% of endemics) cluster of dams • The migration barrier effect will apply to 40 sub‐basins • Hydrologically, the area is dominated by effects of Chinese dams • a drop in the recruitment of local species is expected even in absence of mainstream dams. The contribution of these upstream species to the fish biodiversity of the basin is very important (in particular Balitoridae) • 90% of river will be converted to reservoirs if 6 mainstream dams completed • 41 species at specifically at risk, including the Giant Mekong catfish (at risk for extinction if dams completed) • the risk of fish production losses in case the 6 upstream mainstream dams are built amounts to 130,000 – 270,000 tonnes. Reservoir fish production would range between 2,000 and 20,000 tonnes of fish, the most likely estimate being around 7,000 tonnes of reservoir fish per year in this zone. (2) Middle cluster • 386 species (29% of endemics) of dams • Composed of 40 sub‐basins • The Latsua dam would have much more negative impact on fish migrations than the Ban Koum dam because it would block access to the Mun/Chi system (70,000 km2). The Latsua dam would have the same impact than the Pak Mun dam on Mun‐dependent fish species, plus additional impact on species migrating up the mainstream. • The Ban Koum and Latsua mainstream dams would create 147 km2 of reservoir, i.e. 23% of the mainstream between Pakse and Vientiane would be turned into a reservoir.This area can be expected to produce between 300 and 3,000 tonnes of reservoir fish, the most likely estimate being 330 tonnes • The risk of capture fish production losses in case the 2 mainstream dams of the middle cluster are built amounts to 210,000 – 420,000 tonnes (3) Downstream • 669 species (14% of endemics) cluster of dams • Composed of 24 sub‐basins • Migration barrier: six sub‐basins affected, including the Sekong‐Sesan‐Srepok system (second largest in Mekong, area 78,648 km2) • If 11 reservoirs are built, 55% of the mainstream will be turned into a dam reservoir. If Cambodian dams are not built, “only” 48% of the mainstream would be turned into a lake • The risk of fish production losses in case the 2 mainstream dams of the downstream cluster are built amounts to 220,000 – 440,000 tonnes • The loss of floodplains inherent to these 2 dams corresponds to 3,000 to 12,000 tonnes of fish only • The Stung Treng and Sambor mainstream dams would create 950 km2 of reservoir. This area can be expected to produce between 2000 and 19,000 tonnes of reservoir fish, the most likely estimate being 47,000 tonnes 9.2.2 CROSS‐CUTTING CONCLUSIONS 155 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS Generic non fisheries‐related conclusions • In 2000, 20.6% of the Lower Mekong Basin was already barred by 16 dams and was inaccessible to fish species having to migrate to the upstream parts of the river network. In 2015, this area will have increased by 14% (from 164,000 to 188,000 km2). In 2030, if 11 mainstream dams are constructed, 81.3% of the watershed will be obstructed and floodplain migrant fish will not be able to migrate further than Kratie (Sambor dam). If no mainstream dams are built in Cambodia, then 78.8% of the basin will not be accessible to long distance migrant fish. If mainstream dam development is limited to the 6 dams of the upstream cluster, then 68.7% of the basin will be barred. If no mainstream dams are built, the surface area inaccessible to long distance migrant fish is reduced to 37.3% of the watershed, despite the presence of 77 other dams on tributaries. • The yearly loss in floodplain habitat and in productivity resulting from dam construction should be computed as the sum of losses in wet and in dry season. This corresponds to the surface area that will not be flooded any more in the wet season plus the surface area that will be permanently flooded in the dry season. • Hydrological variations created by dam construction are detailed by the BDP2; however changes forecasted are averages by season and do not reflect daily variations. Important daily variability in downstream water levels following peak operation is a major problem for river ecology, fisheries and riverine livelihoods, as shown by the Yali dam where they have resulted in substantial losses and conflicts. Data on daily variations in flows downstream of planned mainstream dams are not available; however daily fluctuations in the level of the reservoir are expected to reach 2 meters for some projects and give an indication of the daily variability in downstream flows. Such level of variability is expected to have major effects on fish resources and on the environment in general and cannot be ignored in future analyses. • If 11 reservoirs are built, 55% of the mainstream will be turned into a dam reservoir. If 6 dams are built between Chaing Saen and Vientiane, then 90% of the Mekong mainstream between these two points will be turned into a reservoir ecosystem. If Cambodian dams are not built but 9 other mainstream dams are, then 48% of the mainstream would be turned into a reservoir. • An update about the relative share of black fish and white fish basin wide led to the conclusion that that between 35% and 70% of the fish production basin wide is made of long‐distance migratory species vulnerable to mainstream dam development. The current level of knowledge does not allow a lower uncertainty range. • A meta‐review of reservoir fish production led to the conclusion that for mainstream dams, the surface area alone is the best single predictor of reservoir productivity and productivity ranges between 20 kg/ha/year and 200 kg/ha/year. This large range underscores the largely unpredictable nature of reservoir fish production. A combination of surface areas of reservoirs created by mainstream dams and productivity leads to the conclusion that the highest fish production to be expected from reservoir fisheries amounts to 30,000 tonnes basin wide. In fact the most likely production represents about 10,000 tonnes. 9.3 MAINSTREAM DAM CLUSTERS The superimposition of maps of migration zones (Baseline Assessment, section 1.2) and of mainstream dam development leads the identification of three clusters of potential dams of significance to fish production: i) Upper Mekong, from China down to Vientiane (mountainous part of the River, altitude > 200masl); ii) Middle Mekong, from Vientiane down to Pakse (Khorat plateau; altitude between 100 and 200 mamsl); iii) from Pakse down to the 156 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS sea (extensive wetlands and floodplains; altitude <100 mamsl). The first cluster includes all Chinese dams and 6 projects in the Lower Mekong Basin (from Pak Beng to Pakchom); the second cluster includes 2 dam projects in the mainstream (Ban Koum and Latsua); the last cluster includes Don Sahong and the two Cambodian mainstream projects. This clustering corresponds largely to the BDP2 scenarios for 2015 and 2030 (BDP 2010): “2015 definite future” (no mainstream dams), “2030 w/o MS” (no mainstream dams), “2030 w. LMD” (only 6 Lao mainstream dams); “2030 w/o CMD” (no Cambodian mainstream dams, 9 mainstream dams upstream of Cambodia) and “2030 20 year plan” (11 mainstream dams). Table 9.2: Clusters of dams considered in the analysis of fisheries impacts Area Cluster Fish migration zone Dam Installed Operation Reservoir Length Height capacity (?) area (m) (m) (MW) (km2) Gonguoqiao 750 ‐ 3 ‐ 130 Xiaowan 4200 2010 37.14 ‐ 300 Manwan 1500 1993 4.15 ‐ 126 Upper Dachaoshan 1,350 2003 8 ‐ 110 Mekong Nuoshadu 5,500 2017 45 ‐ 254 Jinhong 1500 2009 5.11 ‐ 118 Ganlanba 750 ‐ 0 ‐ ‐ Upstream cluster Upper migration zone Mengsong 400 ‐ 0.58 ‐ ‐ Pak Beng 1230 2016 87 943 76 Luang Prabang 1,410 2016 90 1,106 68 Xayaburi 1,260 2016 49 810 32 Pak Lay 1320 2016 108 630 35 Sanakham 700 2016 81 1,144 38 Pakchom 1079 2017 68 1,200 55 Lower Ban Koum 1872 2017 40 780 53 Mekong Middle cluster Middle migration zone Latsua 686 2018 13 1300 27 1820‐ Don Sahong 720‐ 10.6‐ Downstream cluster Lower migration zone 240 2013 290ha 2730 8.2‐8.3 Stung Treng 980 ‐ 211 10,884 22 Sambor 2,600 2020 620 18,002 56 157 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS Figure 9.115: Clusters of dams considered in the analysis of fisheries impacts 9.3.1 UPSTREAM CLUSTER OF DAMS The upstream zone is mostly within China, and contains 262 species, including 22% of endemics (Baseline Assessment, section 1.2). The analysis below focuses more specifically on the IBFM zone nº2 (Chiang Saen to Vientiane). This zone is bounded by the Chinese border (upstream) and the Pak Chom dam (downstream), and corresponds to the upstream cluster of dams. In this zone the barrier effect on migrations will apply to 40 sub‐ basins47, in particular the large Nam Ou, Nam Mae Kok, Nam Tha, and Nam Khan basins. 47 Nam Mun, 70574 km2; Nam Chi, 49133 km2; Se Bang Hieng, 19958 km2; Nam Ngum, 16906 km2; Nam Cadinh, 14822 km2; Nam Songkhram, 13123 km2; Se Bang Fai, 10407 km2; Se Done, 7229 km2; Nam Nhiep, 4577 km2; Huai Luang, 4090 km2; Huai Khamouan, 3762 km2; Nam Kam, 3495 km2; H.Bang Koi, 3313 km2; Se Bang Nouan, 3048 km2; Huai Tomo, 2611 km2; Nam Hinboun, 2529 km2; Huai Som Pak, 2516 km2; H.Bang Bot, 2402 km2; Tonle Repon, 2379 km2; Nam Sane, 2226 km2; Nam Mang, 1836 km2; Huai Bang I, 1496 km2; O Talas, 1448 km2; Huai Bang Sai, 1367 km2; Nam Suai, 1247 km2; H.Ma Hiao, 990 km2; Nam Mang Ngai, 944 km2; Huai Bang Haak, 938 km2; Nam Thon, 838 km2; Huai Muk, 792 km2; Huai Thuai, 739 km2; Huai Bang Lieng, 695 km2; Huai Ho, 691 km2; Hoaag Hua, 626 km2; H. Khok, 538 km2; Prek Mun, 476 km2; Nam Kadun, 456 km2; Nam Thong, 455 km2; H.Sophay, 186 km2; Phu Pa Huak, 132 km2. 158 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS Figure 9.2: Main river basins in the upstream cluster zone 9.3.2 MIDDLE CLUSTER OF DAMS The middle migration zone is characterized by 386 species and 29% of endemics (Baseline Assessment, section 1.2). This zone corresponds to the middle cluster of dams (Pak Chom dam upstream, Don Sahong dam downstream) and is composed of 40 sub‐basins48, in particular Nam Mun, Nam Chi, Se Bang Hieng, Nam Ngum, Nam Cadinh, Songkhram, Se Bang Fai and Se Done basins. 48 Nam Mun, 70574 km2; Nam Chi, 49133 km2; Se Bang Hieng, 19958 km2; Nam Ngum, 16906 km2; Nam Cadinh, 14822 km2; Nam Songkhram, 13123 km2; Se Bang Fai, 10407 km2; Se Done, 7229 km2; Nam Nhiep, 4577 km2; Huai Luang, 4090 km2; Huai Khamouan, 3762 km2; Nam Kam, 3495 km2; H.Bang Koi, 3313 km2; Se Bang Nouan, 3048 km2; Huai Tomo, 2611 km2; Nam Hinboun, 2529 km2; Huai Som Pak, 2516 km2; H.Bang Bot, 2402 km2; Tonle Repon, 2379 km2; Nam Sane, 2226 km2; Nam Mang, 1836 km2; Huai Bang I, 1496 km2; O Talas, 1448 km2; Huai Bang Sai, 1367 km2; Nam Suai, 1247 km2; H.Ma Hiao, 990 km2; Nam Mang Ngai, 944 km2; Huai Bang Haak, 938 km2; Nam Thon, 838 km2; Huai Muk, 792 km2; Huai Thuai, 739 km2; Huai Bang Lieng, 695 km2; Huai Ho, 691 km2; Hoaag Hua, 626 km2; H. Khok, 538 km2; Prek Mun, 476 km2; Nam Kadun, 456 km2; Nam Thong, 455 km2; H.Sophay, 186 km2; Phu Pa Huak, 132 km2. 159 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS Figure 9.3: Main river basins in the middle cluster zone The two dams of the middle cluster will have very different impacts on fish, since Latsua and Ban Koum dams are located upstream and downstream, respectively, of the mouth of the Pak Mun tributary (Figure 4). With an area of 119,707 km2, the Mun/Chi River is the biggest hydrological basin the Mekong. Figure 9.4: Location of Ban Koum and Latsua dams and barrier effect on the Mun/Chi sub‐basins 160 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS 9.4 DOWNSTREAM CLUSTER OF DAMS Figure9.5: Main river basins in the middle cluster zone The lower migration zone contains 669 species and 14% of endemics (Baseline Assessment, section 1.2). This zone corresponds to the downstream cluster of dams (Don Sahong dam upstream, Sambor dam downstream) and is composed of 24 sub‐basins49. However in this lower migration zone only six sub‐basins will be subject to the barrier effect of mainstream dams: Se Kong, Se San, Sre Pok, Prek Preah, Prek Krieng, and Prek Kamp basins. The Sekong‐Sesan‐Srepok system, converging upstream of Stung Treng, is the second largest hydrological sub‐basin in the Mekong after the Mun/Chi system and has an area of 78648 km2. The area downstream of Sambor dam, including the delta and the Tonle Sap sub‐basin, is not affected by the barrier effect only by the hydrological modifications induced by these dams. 9.4.1 OVERVIEW Table 9.3 show the proportion of the Lower Mekong watershed located upstream of the dams being considered. This confirms that three dams, namely Ban Koum, Latsua and Stung Treng, have a proportionally greater share of watershed than others. 49 Delta, 48235 km2; Sre Pok, 30942 km2; Se Kong, 28815 km2; Se San, 18888 km2; St. Sen , 16360 km2; St. Mongkol Borey , 14966 km2; St. Sreng , 9986 km2; Siem Bok , 8851 km2; St. Chinit , 8237 km2; St. Baribo , 7154 km2; Prek Thnot, 6124 km2; St. Pursat , 5965 km2; Prek Chhlong , 5957 km2; Prek Te, 4364 km2; St. Staung , 4357 km2; St. Battambang , 3708 km2; St. Dauntri , 3696 km2; St. Siem Reap , 3619 km2; Prek Krieng, 3332 km2; Tonle Sap , 2744 km2; St. Chikreng , 2714 km2; Prek Preah, 2400 km2; St. Sangker , 2344 km2; Prek Kamp, 1142 km2; 161 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS Table 9.3: Watershed area upstream of each mainstream dam Cluster Project name Watershed area upstream % of LMB watershed upstream of the dam (km2) 1 Pakbeng 218,000 27.4 1 Luangprabang 230,000 28.9 1 Xayabuly 272,000 34.2 1 Paklay 283,000 35.6 1 Sanakham 292,000 36.7 1 Pakchom 295,500 37.2 2 Ban Koum 418,400 52.6 2 Latsua 550,000 69.2 2 Don Sahong 553,000 69.6 3 Stung Treng 635,000 79.9 3 Sambor 646,000 81.3 LMB 795,000 Source: MRC data (BDP2) Figure 9.616: Mainstream dams and corresponding upstream watershed area In the Mekong Basin long‐distance fish migrations occur at a large scale between downstream floodplains and the upstream sections of the Mekong and its tributaries (Baseline Assessment, section 5.4). For this reason the proportion of the upstream section of the Mekong watershed blocked by dam gives an indication of the surface area or habitat that will become inaccessible to migrant fish. In order to assess that surface area, dams have been classified by watershed then by river; the area blocked by the dam located furthest downstream is inaccessible to fish. This area was quantified for each basin and for 3 periods of time: 2000 (baseline), 2015 (Definite future) and 2030. For 2030, the scenarios detailed are i) no mainstream dams; ii) 6 mainstream dams in the upstream cluster; iii) no mainstream dams in Cambodia, and iv) 11 mainstream dams (details in Annex 1). The table below summarizes the findings: 162 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS Table 9.4: Surface area of the Lower Mekong Basin blocked by dams under different scenarios 2000 2015 2030 S1. Area S2. Area S2 S3. No Area Baseline S1 Definite MS S3 future dams Nb of dams / km2 obstructed for migrations 16 164148 47 187695 77 296568 % of LMB obstructed for migrations 20.6 23.6 37.3 LMB area (km2) = 795,000 2030 S4. 6 MS Area S5. No Area S5 S6. All Area dams in S4 Cam 11 MS S6 upper MS dams LMB dams Nb of dams / km2 obstructed for migrations 83 545901 86 621998 88 646000 % of LMB obstructed for migrations 68.7 78.2 81.3 Km2 obstructed specifically by LMB mainstream dams S4 ‐ S3 = 249333 S5‐S3 = 325430 S6 ‐ S3 = 349432 % of LMB obstructed specifically by mainstream dams 31 41 44 Sources: Description of BDP2 scenarios dated 21‐12‐2009 Conclusions: In 2000, 20.6% of the Lower Mekong Basin was already barred by 16 dams and was inaccessible to fish species having to migrate to the upstream parts of the river network. In 2015, this area will have increased by 14% (from 164,000 to 188,000 km2). In 2030, if 11 mainstream dams are constructed, 81.3% of the watershed will be obstructed and floodplain migrant fish will not be able to migrate further than Kratie (Sambor dam). If no mainstream dams are built in Cambodia, then 78.8% of the basin will not be accessible to long distance migrant fish. If mainstream dam development is limited to the 6 dams of the upstream cluster, then 68.7% of the basin will be barred. If no mainstream dams are built, the surface area inaccessible to long distance migrant fish is reduced to 37.3% of the watershed, despite the presence of 77 other dams on tributaries. Since many dams on tributaries already exist or are planned, mainstream dams will not be the only cause of the barrier effect on fish migrations. The proportion of the total impact attributable to mainstream dams can be quantified by subtracting the area barred by tributary dams from the overall area barred. These results indicate that the cluster of 6 mainstream dams in upper Laos would obstruct 31% of the migration routes (but not of the migration themselves), that all LMB mainstream dams would obstruct 44% of the Lower Mekong Basin, and that in the presence of 9 other mainstream dams the Cambodian mainstream dams alone would obstruct only 3% of the basin, because most of the basin area between Sambor and Latsua (5 watersheds including Sekong, Sesan and Srepok watersheds) would already be obstructed by 21 tributary dams. 9.5 FORECASTED HYDROLOGICAL CHANGES RELATING TO FISHERIES The dams planned will bring about a number of hydrological changes of importance for fish: i) flow reduction in the wet season and floodplain area: the Mekong system has the most productive fishery of the world because of its large floodplain and its hydrological variability. If the flow is lower in the wet season, in some places water might not reach the level of the banks and thus not spill over in plains, or not spill as far as before, which would mean a loss of habitat for fish; ii) flow increase in the dry season: some land areas that used to be dry in the dry season will become permanently flooded, and thus will lose the productivity that results from the seasonal inundation (Junk et al. 1989). As a consequence, the yearly loss in floodplain habitat and in productivity resulting from dam construction should be computed as the sum of losses in wet and in dry season (loss in variability). This corresponds to the surface area that will not be flooded any more in the wet season plus the surface area that will be permanently flooded in the dry season (double ring illustrated in Figure 7). 163 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | AQUATIC SYSTEMS Figure 9.7: Change in flooding due to dams and loss of productivity Floodplain before the dam Dry season water level Wet season water level Floodplain after the dam Area not flooded any more in the wet season New area permanently flooded in the dry season Areas characterized by loss of productivity (by loss of flood pulse) Source: Baran et al. in press. In the past years a number of studies have attempted to quantify these changes. For this SEA the reference predictions used are those of the on‐going BDP2 analysis, since they based on the most updated and accurate set of scenarios. However we also included, for information, the predictions from three other large modelling studies: i) the WorldBank Mekong development scenarios (Podger et al. 2004); ii) the Nam Theun 2 Cumulative Impact Analysis (Norplan and Ecolao 2004); and iii) the BDP 1 scenarios for strategic planning (MRC 2005). The results of these respective studies are summarized below for comparison with the BDP2 scenarios. All former studies are characterized by a small number of dams, and thus can only be compared with the BDP2 2015 scenario. Table 9.5: Development scenarios in recent hydrological modelling studies WorldBank 2004 Nam Theun 2 2004 BDP 1 2005 BDP 2 2009/2010 High development (25 2025 (28 dams basin High development (21 2015 Definite future (47 dams basinwide) wide) dams basin wide) dams basin wide) 2030 no LMB mainstream dams (77 dams basin wide) 2030 with 6 Lao mainstream dams (83 Scenarios dams basin wide) 2030 with 9 mainstream dams not in Cambodia (86 dams basin wide) 2030 with 11 mainstream dams (88 dams basin wide) The hydrological consequences forecasted by the different studies are detailed in the table below. The results from the on‐going BDP2 modelling work have been extracted from detailed hydrological forecasts provided, from Technical notes 1, 2 and 4 dated February 2010 and corresponding presentations (www.mrcmekong.org/programmes/bdp/BDP‐submissions.asp). 164 ICEM – International Centre for Environmental Management Table 9.6: Hydrological changes forecasted by different studies for 5 scenarios Definite Future 20Y w/o MD 20Y with LMD 20Y no CMD 20Y 2015 2030, no mainstream dams 2030, 6 mainstream dams 2030, 9 mainstream dams 2030, 11 mainstream dams Discharge in WL in wet FA, wet Discharge, dry WL, wet Discharge WL, wet FA, wet Discharge, WL, wet FA ,wet Discharge WL in FA in wet dry season (% season (change season (% season (% season in dry season season dry season season season in dry wet season (% change from from baseline change change from (change season (% (change (% (% change (change (% season (% season change baseline) in m) from baseline) from change from change from from change change (change from baseline) baseline from baseline from baseline) baseline from from from baseline) in m) baseline) in m) baseline) in m) baseline) baseline) baseline in m) Luang Prabang BDP1: +55 BDP1: ‐1.5 BDP2: +65.2 BDP2: 0 BDP2: BDP2: ‐ BDP2: 59.7 BDP2: ? BDP2: BDP2: ‐ +58.3 0.7 +59.7 0.7 BDP2: +45.4 BDP2: ‐0.6 Nong Khai/ WB: +47 to 73 WB: ‐0.5 to 1.0 BDP2: +52.7 BDP2: ‐ BDP2: +54 BDP2: ‐ BDP2: 54.8 BDP2: ? BDP2: BDP2: ‐ Vientiane 0.5 0.5 +55.2 0.5 BDP2: +41.4 BDP2: ‐0.5 Savannakhet/ WB: +30 to 52 WB: ‐0.4 to 0.7 BDP2: +31 BDP2: ‐ BDP2: BDP2: ‐ BDP2: ? BDP2: BDP2: ‐ Pakse 0.4 +32.1 0.5 +33.3 0.5 NT2: +135 NT2: ‐1.6 BDP1: +33 BDP1: ‐0.7 BDP2: +31.6 BDP2: ‐0.3 BDP2: 32.6 Kratie WB: +22 to 45 WB: ‐0.4 to 0.8 BDP2: +25.3 BDP2: ‐ BDP2: BDP2: 27.4 BDP2: ? BDP2: +28 BDP2: ‐ 0.6 +26.1 0.6 NT2: +125 BDP1: ‐0.8 BDP1: +27 BDP2: ‐0.3 BDP2: +22.4 Tonle Sap NT2: +0.63 NT2: ‐0.54 NT2: ‐8.7 BDP2: ? BDP2: ? BDP2: ? BDP2: ? BDP2: ? BDP2: BDP2: ‐ BDP2: ‐7 BDP1: ‐0.4 BDP1: ‐3.4 0.46 (Cambodia BDP2: ? BDP2: ‐0.26 BDP2: ‐5 and LMB) (Cambodia and LMB) Tan Chau BDP1: +26 WB: ‐0.2 to 0.3 BDP2: +13.1 BDP2: ‐ BDP2: BDP2: ‐ BDP2: 13.7 BDP2: ? BDP2: BDP2: ‐ 0.2 +13.8 0.2 +14.9 0.2 BDP2: +13.3 BDP1: ‐0.2 BDP2: ‐0.3 Whole BDP2: ‐ BDP2: ‐ Cambodia 104,000 ha 142,000 ha BDP2: ‐ BDP2: ‐ Whole Basin 251,000 ha 309,000 ha BDP1: Basin Development, phase 1; BDP2: Basin Development Plan phase 2; NT2: Nam Theun 2; WB: WorldBank Q: discharge; WL: Water level; FA: Flooded area 165 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | FISHERIES Conclusions: In the Definite Future scenario, when comparing to the 2000 baseline, BDP2 (technical notes 1 and 2 and presentations dated February 2010) predicts that dry season discharge will increase by 45% in Luang Prabang, 32% in Pakse, 22% in Kratie and 13% in Vietnam. These estimates are close to estimates from BDP1 and WorldBank studies, within a range of about 10%. This is surprising since the number of dams integrated in the BDP1 and WorldBank studies is only about half of those integrated in the BDP2 studies, which would indicate that an additional 19 to 26 dams in the basin would not make much difference for discharge levels in the dry season. Changes predicted by the Nam Theun 2 study are much more dramatic, with a dry season discharge doubling in Pakse and Kratie. In the wet season, the variable common to all studies is the water level, not discharge. According to BDP2, wet season water level is expected to be reduced by 30 to 60 cm maximum, depending on places. Previous studies tend to forecast that the reduction of water level will be higher by 10 to 90 cm. None of the former studies analysed scenarios for 2030, and thus cannot be compared to BDP2. BDP2 forecasts that twenty years from now, in the absence of mainstream dams, discharge in the dry season will be between 13% and 65% higher than in 2000 (higher values upstream). With 6, 9 or 11 mainstream dams in the Lower Mekong Basin the range will be approximately the same (13% to 58%) because most of these mainstream dams are considered run‐of‐the‐river. The same applies to water level in the wet season, with a decrease of between 20 cm and 70 cm maximum depending on the location (more losses upstream), for all scenarios. It is important to note that hydrological changes forecasted by the BDP2 are averages by season which do not reflect daily variations. Important daily variability in downstream water level following peak operation is a major problem for river ecology, fisheries and riverine livelihoods, as shown by the Yali dam. Downstream of Yali dam in Cambodia, until at least 2003, daily fluctuations ranging between 50cm and one meter have resulted in dramatic losses in habitat, fish resources, livestock, and at least 39 casualties downstream of Yali dam (Fisheries Office of Ratanakiri Province, 2000;McKenney 2001; Baird et al. 2002, Lerner 2003, Baird and Meach 2005, Wyatt and Baird 2007). Data on daily variations in flows downstream of planned mainstream dams are not available; however expected daily fluctuations in the level of the reservoir (i.e. upstream) are indicated for some projects and give an indication of the daily variability in downstream flows. In the case of Luang Prabang, Latsua and Stung Treng dams, two meters of daily fluctuation correspond respectively to 87, 23 and 428 million cubic meters (see Table 9.7). Such level of variability is expected to have major effects on fish resources and on the environment in general and cannot be ignored. However the complete absence of data about this phenomenon did not allow factoring it into the current impact analysis. The latest BDP2 scenarios for 2015 predict a loss of 1040 km2 of floodplains in Cambodia compared to the situation in 2000, and of 2510 km2 for the whole Mekong Basin (‐5%). In 2030, with 11 mainstream dams, a total loss of 1420 km2 and 3090 km2 is forecasted in Cambodia and in the whole Basin respectively (‐7%). It is not clear whether the loss of floodplain area forecasted by the BDP2, which seems relatively limited (7% loss maximum after the total number of dams has increased from 16 dams in 2000 to 88 in the 2030 11 MD scenario), includes the double ring detailed above. Regarding the Tonle Sap area (an area that generates 60% of the Cambodian fish production), some additional forecasts are proposed by the BDP2 (BDP2 2010): 166 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | FISHERIES • Reduction of the total flooded area by 60,000 ha (4.5 %) in an average year, and as much as 100,000 ha (9%) in a dry year; • Reduction of the area of flooded forest by 5,000 ha (1.1%) in an average year to 23,000 ha (5.3 %) in a dry year; • Reduction of the area of inundated grasslands by 8,500 ha (3.2%) in an average year to 25,000 ha (10 %) in a dry year; • Reduction of the area of flooded marshes by 3,000 ha (1.0%) in an average year to 5,500 ha (1.8 %) in a dry year; • Reduction of the area of flooded rice fields of 41,000 ha (18%) in an average year and 48,000 ha (28 %) in a dry year; • Reduction of flood depth of just over 0.5 m in an average and dry year; • Reduction of flood duration of the flooded forest area by generally less than 2 weeks in an average year, but up to 1 month in a dry year; • Reduction in flood duration by generally less than 1 month in an average year in 70% of the inundated grassland area, but an increase of flood duration with up to 1 month in 25% of the area; • Increase of the water level in the dry season with about 30 cm, resulting in a volume increase of 780 MCM, or an increase of over 50%; • Reduction of sediment inflow in the system of at least 8 to 13%. Table 9.7: Mode of operation of the planned mainstream dams and expected daily fluctuation in the reservoir level (Source: SEA Inception Report Vol 2) Mode of operation Daily fluctuations in the reservoir (m) Pak Beng NA NA Louang Prabang peak load 12‐15 h/day ‐2m Xayaburi NA 0 Pak Lay Peak load 8‐10 hours/day 1‐2 m Sanakham NA NA Pakchom Continuous ‐ 2m Ban Koum Continuous NA Latsua Peak load >16 hours/day ‐2m Don Sahong Continuous NA Stung Treng Continuous 2m Sambor NA small 9.6 WETLANDS, FLOODPLAINS AND FISH PRODUCTIVITY Changes in floodplain areas highlighted in Table 9.5 imply changes in related fish production. This relationship between wetland or floodplain area and fish yield has been studied in detail and the comprehensive reviews done by Hortle (2007) and Hortle et al. (2008) are summarized below. 167 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | FISHERIES Welcomme (1985) estimates that floodplain area can predict 70% of floodplain river productivity, and 40‐ 60 kg/ha/year is a typical range for tropical floodplain rivers. In the LMB, however, natural productivity exceeds that of many other tropical floodplains, and is estimated to range between 25 and 630 kg/ha/year, with a mean yield of 119 ± 25 kg/ha/year (average of 18 studies, details in Hortle et al. 2008, p. 39). This value is lower and more accurate than the 230 kg/ha/year mentioned in Baran et al. (2001) and Sverdrup‐Jensen (2002)50). To reflect the variability in floodplain productivity, Hortle (2007) used low, medium, and high values of productivity per hectare (respectively 50, 100, and 200 kg/ha/year) and confirmed this range later on (Hortle et al 2008), insisting on the middle value (119 ± 25 kg/ha/year) as the most likely average figure. Notes: • when relating floodplain productivity, floodplain area and total production, the most recent wetland surface area estimates available and published are those detailed in Hortle et al. (2008, p. 40), updating those of Hortle 2007. • there is confusion in the literature between wetlands, floodplains and rice field areas. Multiple authors do not differentiate between floodplains and wetlands, although Hortle et al. (2008) distinguish between wetlands, rice fields, swamps, flooded natural vegetation and permanent water bodies. However in the surface areas detailed by these authors, rainfed rice fields (RRF) are lumped with flooded rice fields, although it is acknowledged that the productivity of the latter (around 200 kg/ha/y) is double that of the former. • in the unofficial IBFM report nº 8 (King et al. 2005), fish productivity per hectare is not detailed, but a non‐linear relationship is assumed and it is estimated that a 10% reduction in floodplain area would result in a 20‐30% reduction in fisheries productivity. This study also points out that loss of production in due to reduced floodplain area can be exacerbated by a delayed flood duration (issue highlighted and detailed in Baran et al. 2001, 2005, and Kurien et al. 2006) 9.7 LONG‐DISTANT MIGRANTS AND MEKONG FISH PRODUCTION A number of Mekong fish species migrate between floodplains and tributaries, but details about where they migrate to have never been summarized. For this study we reviewed existing information to characterize the migration of as many species as possible, and combined this information with the contribution of these species to total catches. The methods are detailed below, and results will be detailed for each dam cluster in a following section. 9.7.1 MIGRATION PATTERNS OF DOMINANT SPECIES This synthesis is initially based on migration maps available for 23 species in the Mekong Fish Database (MFD 2003, see Annex 2). On each map five barriers have been represented: i) Sambor blocking migrations upstream and towards the 3S system; ii) Stung Treng/Don Sahong blocking migrations through 50 yet figures of total production in these studies are close to Hortle’s figures because the surface area of wetlands was updated. 168 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | FISHERIES Khone Falls; iii) Latsua blocking migrations towards the Mun/Chi system; iv) Ban Koum blocking migrations towards Vientiane, and v) the upstream cluster blocking access to the upstream migration zone. This analysis of 23 fish taxa was complemented by a synthesis of all ecological information published in Mekong Fish Database and in FishBase, obtained by merging these two databases (FishBase having more information on the taxonomy and biology of the species, and Mekong Fish Database on their ecology and distribution). This combination provides information (with more or less details depending how well a given species is known) for 768 species. An example of the information synthesized is given in Annex 3 for two well‐known migrant species. The analysis focused on six main upstream migration patterns : i) fish migrating from floodplains up to Kratie/Sambor; ii) fish migrating to the 3S system (Sekong‐Sesan‐Srepok); iii) fish migrating through Khone Falls; iv) fish migrating to the Mun/Chi system; v) fish migrating upstream of Pakse; vi) fish migrating upstream of Vientiane. Ultimately a total of 46 species displaying particular migration patterns or critical habitats in the different zones describe above were identified. The matrix of species by zone (Annex 4) was complemented by the contribution of each species to total catches basin wide, based on data detailed in section 5.2.1). A summary of that information is detailed in Table 9.8. Table 9.8: Summary of the migration patterns of 43 species dominant in catches51 Migration Migration Migration All Migratio Migration through to the Migration upstream species n up to to the 3S Khone Mun/Chi up to of reviewed Kratie system Falls system Vientiane Vientiane Number of 43 43 25 41 15 28 27 species % of species 100 100 58 95 35 65 63 reviewed Note: This review only reflects the status of our knowledge about migrations in relation to a few key locations in the basin, as mentioned in the scientific literature and in databases. This review is also based on information available in written form in the two databases cited; there is additional information about migrations available but it is coded (e.g. migration timing of Hypsibarbus malcolmi in multiple locations in the Basin) and the 10 days of work available for this review of impacts did not allow systematically analysing that raw information. Some other species living in the mainstream such as Gyrinocheilus aymonieri represent 1.63% of catches basin wide but they do not exhibit long‐distance migration patterns, and although they might be at risk of mainstream dam development, they have not been covered in the present analysis Conclusions: This analysis focused on 43 white fish species whose long‐distance migration patterns are well known, and making up to a third of the fish catch basin wide. Out of these species, all exhibit a migration pattern between downstream floodplains and the Mekong mainstream by Kratie; 95% of them (= 28.5% of the catch basin wide) migrate through Khone Falls; and about two‐thirds undertake a migration between Khone Falls and upstream (towards tributaries of the middle Mekong migration system, or upstream of Vientiane). 51 This analysis assumes that the downstream floodplains in Cambodia and Vietnam are a starting point, and considers only upstream long distance migrations. Migration within sub‐systems, from floodplains to local tributaries or lateral migrations between close habitats are not reflected here. 169 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | FISHERIES Several limitations to this approach must be highlighted: i) upstream of Kratie it is impossible to assess how much of the catch the migrant species identified represent (what is known is only their contribution to the overall catches); to do so it would be necessary to know the catch per river stretch; this information is available in raw MRC data (see section 5.2.1) but has never been analysed so far; ii) the fact that a species migrates to a certain zone does not mean that it is specific to that zone (thus 22 of the 25 species migrating to the 3S system are also found upstream of Vientiane) nor that access to this zone is absolutely necessary to the reproduction of that species; iii) for some species there could be sub‐populations able to complete their life cycle within segments of the basin (e.g.: between Cambodian floodplains and the 3S system, between Thai floodplains and the upstream Mekong) without having to migrate through the whole basin. Figure 9.8: Number of species of long‐distance migrants found in the sections of the LMB possibly barred by mainstream dams 9.7.2 DOMINANT SPECIES IN MEKONG FISH CATCHES A debate has recently surfaced about the species composition in catches basin wide, and the relative proportion of black fish in the overall catch. This is important because the impact of dams is likely to be much less severe for black local fish than for white migrant fish (Baseline Assessment, section 6.2). We review below some approaches that either identified dominant species in overall catches, or quantified the share of black fishes in overall catches. Note: strictly speaking, the term of “black fish” refers to floodplain fishes only, and thus to species found in floodplain or wetlands. This term should not be used for non‐migratory species found upstream of tributaries and in stream environments. 170 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | FISHERIES METHOD 1: CATCH MONITORING IN THE MAINSTREAM Figure 9.9: Site locations of the AMCF fishermen’s catch monitoring survey. Fish abundance and diversity have been monitored basin wide based on gillnets operated by local fishermen (Starr 2008). This monitoring undertaken by the MRC Assessment of Mekong Capture Fisheries Project was carried out in the four LMB countries between 2002 and 2005. At each selected site three fishermen using gillnets recorded species caught daily, in different types of habitats: the main channel of the Mekong River, deep pools in the mainstream and along three tributaries, and in the delta. Data used in the analysis below correspond to the December 2003 – November 2004 period. Data from this monitoring have been processed and made public for the first time in Halls and Kshatriya (in press). This study reflects catches of one specific gear only (gill nets) and is restricted to large rivers (mainstream and main tributaries), without covering floodplains and wetlands. Despite a subsequent underestimate of the production of black fish, this study is by far the most detailed source of information available to date when dealing with fish catches at the species level and basin wide. The AMCF survey resulted in reports about a total of 233 species of fish belonging to 55 families. Twenty‐ two species (9.4% of the species richness sampled) were identified as black fish and 150 species (64.4%of the total richness) were identified as white fish. Among those, 58 white fish species (24.9% of the species richness sampled) representing 38.5% of the total catch were considered highly vulnerable to dam development (the criteria for classification, the 58 species, and their share in catches basin wide are detailed in Annex 5. From this assessment it can also be deduced that 100‐38.5 = 61.5 % of the catch is made of species that are not highly vulnerable to dam development (this latter category includes black fish and other species). METHOD 2: SURVEYING EXPERTS 171 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | FISHERIES In the first half of 2007, the MRC Fisheries Programme gathered an expert panel consisting of 13 fisheries scientists from Lao PDR, Cambodia and international research organizations operating in the LMB to provide an estimate of the size and value of the migratory fish resource in the LMB (details in Barlow et al. 2008). Experts were asked “What percentage of the total yield from the capture fishery in the LMB is ‘white fish’ (that is, those that are highly migratory)? The combined answer was that migratory fish resources vulnerable to mainstream dam development comprise 71% of the fisheries yield in the LMB. METHOD 3: CATCH STATISTICS IN CAMBODIA In 2000, van Zalinge and his colleagues, summarizing several years of fish monitoring by the MRC/DoF/DANIDA project "Management of the Freshwater Capture Fisheries in Cambodia" (Diep Loeung et al. 1998), reached the conclusion that “longitudinal migrants constitute about 63 % of the total catch taken by fisheries in the Tonle Sap area” (van Zalinge et al. 2000). This proportion might somehow be an overestimate since the fishery best monitored was the dai fishery targeting white migrant fish, whereas the species composition in dispersed small‐scale and familial fisheries and in the non‐transparent large scale fishing lots was not well known. METHOD 4: UPDATE INTEGRATING BLACK FISH PRODUCTION IN RICE FIELDS In 2008, Hortle et al. looked in detail that the production of rice field fisheries in Cambodia, and found that 87.7% of the catch in rice fields is made of black fish, and that rice fields represent 86.1% of wetlands in the Lower Mekong Basin52. We used this update to determine the contribution of black fish to fish production basin wide; the steps of this assessment are detailed below: • Wetlands = floodplains + rice fields + other wetland types • Rice fields = floodplain rice fields (high fish productivity) + rainfed rice fields (RRF, lower fish productivity) • Other wetland types = permanent water bodies + aquaculture + swamps + flooded forest/grassland/shrubs Surface area of wetlands = surface area of floodplains (including floodplain rice fields) + rainfed rice fields + permanent water bodies + aquaculture + swamps + flooded forest/grassland/shrubs Surface area of rainfed rice fields = surface area of wetlands ‐ floodplains ‐ permanent water bodies ‐ aquaculture ‐ swamps ‐ flooded forest/grassland/shrubs Surface area of Wetlands in the LMB: 184,900 km2 (Hortle et al. 2008 p. 40) Surface area of floodplains in the LMB: 50,152 km2 (TKK & START‐RC 2009 p. 22). Surface area of rice fields: 159,200 km2 (Hortle et al. 2008 p. 40) Surface area of permanent water bodies: 13,800 km2 (Hortle et al. 2008 p. 40) Surface area of aquaculture: 2,400 km2 (Hortle et al. 2008 p. 40) Surface area of swamps: 2,200 km2 (Hortle et al. 2008 p. 40) Surface area of flooded forest/grassland/shrubs: 7,300 km2 (Hortle et al. 2008 p. 40) → Surface area of rainfed rice fields = 109,000 km2 52 However a detailed analysis of productivity by wetland type, based on the reviews detailed in Hortle (2007) and Hortle et al. (2008), and detailed in another section of this report, leads to the conclusion that rice fields produce around 100 kg of fish per hectare and per year, whereas floodplains produce around 200 kg per hectare and per year. 172 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | FISHERIES • Production of RRF = productivity of RRF x surface area of RRF = Y% of (black fish)RRF Productivity of RRF: around 100 kg/ha/y (Hortle et al. 2008 p.41) Surface area of RRF: 109,000 km2 = 10,900,000 ha Fish production of rainfed rice fields = 1,090,000 tonnes Percentage of black fish in rainfed rice fields: 88% (Hortle et al,. 2008 p. 19) Percentage of white fish in rainfed rice fields = 100 – 88 = 12% (Hortle et al,. 2008 p. 19) → Production of black fish in rainfed rice fields = 1,090,000 x 0.88 = 959,000 tonnes → Production of white fish in rainfed rice fields = 1,090,000 x 0.12 = 131,000 tonnes • Production of fish basin wide: 2.1 million tonnes (based on consumption studies; Baseline Assessment section 2.1.2.) • Production (tonnes) of fish basin wide = production of Flood Plains + production of Rainfed Rice Fields Production of Flood Plains = Production basin wide (2,100,000 t) ‐ Production of RRF (1,090,000 t) → Production of Rainfed Rice Fields = 1.01 million tonnes (made of white fish and black fish) • In the Tonle Sap (i.e. floodplain system), the proportion of white fish reaches 63% (van Zalinge et al. 2000) and thus the proportion of black fish is 100‐0.63 = 37% → Production of white fish in floodplains = 1,010,000 x 0.63 = 636,000 tonnes → Production of black fish in floodplains = 1,010,000 x 0.37 = 374,000 tonnes • Total production of black fish: 959,000 tonnes from rainfed rice fields + 374,000 tonnes from floodplains = 1.33 million tonnes, out of 2.1 million tonnes = 63% → Production of black fish basin wide = 1,010,000 x 0.63 = 636,000 tonnes → Percentage of black fish basin wide = 63% So based on estimates of black fish proportion in rainfed rice fields and in actual floodplains, and on the respective proportion of each habitat type in the LMB, there would be 63% of black fish in the total fish production of the Mekong Basin. As a consequence, migratory fish resources vulnerable to mainstream dam development would represent 37% of the fisheries yield in the LMB. OVERVIEW From the table below it can be concluded that between 35% and 70% of the fish production basin wide is made of long‐distance migratory species vulnerable to mainstream dam development. The current level of knowledge does not allow a lower uncertainty range. Applying these figures to the estimates of total fish production detailed in the Baseline Assessment (section 2.1.2 and Table 9.9 below) —with a focus on catch estimates based on consumption studies since they are the most robust— shows that the total fish production at risk of mainstream dam development ranges between 700,000 tonnes and 1.4 million tonnes (170,000 – 340,000 tonnes for Cambodia, 60,000 – 120,000 tonnes for Laos, 250,000 – 500,000 tonnes for Thailand and 240,000 – 480,000 tonnes for Vietnam). 173 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | FISHERIES Table 9.9: Percentage of the catch made of species not highly vulnerable to dam development (black fish or others) Percentage of the catch made of fish Quality of the vulnerable to dam development estimate Mainstream catch 38.5 ** monitoring Expert judgment 71 * Catch statistics in 63 * Cambodia Integration of rice fields 37 ** 9.8 GAINS IN FISH PRODUCTION FROM DAM RESERVOIRS Utilization of dam reservoirs for fish stocking is often mentioned as a way to increase fish production; this production depends on the characteristics of the reservoir considered. Table 9.10 details the specifications of reservoirs created behind each of the 11 mainstream dams; it was generated by the SEA GIS team, based on a digital terrain model and the specifications of each dam. Table 9.10: Characteristics of each mainstream dam reservoir Reservoir Area (km2) Average Maximum % of total volume at depth depth (m) volume < 2 m < 5 m (mcm) Pak Beng 87.77 3.1 275.3 22.94 53.28 Louang Prabang 62.38 12.9 802.1 10.84 26.93 Xayaburi 50.43 7.4 374.7 86.57 93.69 Pak Lay 76.65 5.1 388.7 19.74 47.68 Sanakham 70.46 53.7 3783.6 3.29 8.16 Pakchom 55.76 1.7 97.2 78.23 92.33 Ban Koum 133.69 4.7 634.3 10.8 25.95 Latsua 13.33 9 119.4 19.43 45.96 Don Sahong 2.89 10.6 30.5 16.36 40.58 Stung Treng 234.23 6.6 1548.9 27.62 64.72 Sambor 715.89 4.9 3488.4 31.3 63.07 The proportion of the total volume of the reservoir between the surface and ‐2m or ‐5m characterizes the shape of the reservoir, and subsequently its fish productivity since the latter is concentrated in the water closest to the surface, with deeper waters being less productive (Bernacsek, 1997). 174 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | FISHERIES According to Bernacsek (1997), assessing production potential requires data about annual affluent flow volume in each reservoir. This information was derived, for each main scenario, from annual discharge volumes in dry and wet seasons in the upstream hydrological station nearest of each reservoir. Table 9.11: Annual effluent flow volume in each reservoir (million cubic meters) Reservoir Upstream station Baseline Definite future 2030 Pak Beng Chiang Saen 83.1 82.9 82.7 Louang Prabang Louang Prabang 120.1 119.7 122.6 Xayaburi Louang Prabang 120.1 119.7 122.6 Pak Lay Louang Prabang 120.1 119.7 122.6 Sanakham Louang Prabang 120.1 119.7 122.6 Pakchom Chiang Khan 132.4 132.0 134.7 Ban Koum Mukdahan 238.4 236.8 228.6 Latsua Pakse 296.6 294.5 285.7 Don Sahong Pakse 296.6 294.5 285.7 Stung Treng Pakse 296.6 294.5 285.7 Sambor Kratie 296.6 294.5 285.7 The yields obtainable from reservoir fisheries vary considerably between reservoirs and depend on size and on multiple other factors. Small and shallow reservoirs are considerably more productive than large and deep ones (Bernacsek 1997). Productivity of reservoirs in southeast Asia ranges between a maximum yield of 200 kg/ha/year (China, Vietnam) and a few kilograms per hectare per year in Thailand, Indonesia or in Malaysia (Bernacsek 1997, Jackson and Marmulla 2001). Even with regular stocking, yields from large reservoirs in Thailand have been consistently below 200 kg/ha/year (Amornsakchai et al. 2000). In Pak Mun the reservoir fish production was expected to amount to 220 kg∙ha‐1 but it actually reached only about 10 kg.ha‐1 (Amornsakchai et al. 2000,. Jutagate et al. 2001) In India, large‐ and medium‐size reservoirs have been found unsuitable for self‐sustaining production, and depend on continuous stocking (Bernacsek 1997a; Jackson and Marmulla 2001). Overall, the large uncertainty throughout Asia in yields achievable in newly created reservoirs seriously hampers the credibility of reservoir fish production predictions (Bernacsek 1997). Generally speaking, during the first ten years after impoundment, fish in reservoirs benefit from a high primary production and catches are very high, but this period is followed by a progressive then sharp decline (review in Baran et al. in press). In addition to biological issues, varying degrees of reservoir management (Jutagate et al. 2006) and socio‐economic issues (access rights, availability of fingerlings, market competition, etc) are often another major reason behind the failure of reservoir fish production systems (De Silva and Funge‐Smith 2005). For instance, South America has a long experience of dam development and results from stocking in large reservoirs in South America have been meager or null (review in Quirós, 1999). Nam Ngum in Laos seems to be an exceptional case: the reservoir is still productive (13.8 kg/ha/year, around 600 tonnes/year, Bernacsek 1997) after three decades of exploitation. The reasons behind this sustained productivity are not well understood. Other reservoir fisheries in the region have on the contrary been quite disappointing, and there is a risk that a “success story” such as Nam Ngum will give a false impression that reservoir fisheries are a very productive option likely to compensate for the loss of capture fish resources. 175 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | FISHERIES 9.8.1 ESTIMATES OF PRODUCTIVITY BASED ON SURFACE AREA, DEPTH AND FLOW Bernacsek, in his extensive review of more than 26 large dam fisheries in the Lower Mekong commissioned by the MRC in 1997, showed that the potential productivity of a reservoir was best predicted by its surface area, its depth, and the water inflow in that reservoir. C = 1.877A ‐12D + 0.03835I + 126.8 where C = catch (tonnes/year), A = surface area (km2), D = depth (m) and I = affluent flow (cmc/year) Productivities calculated in this manner for mainstream dam reservoirs, using information summarized in Tables 9.9 and 9.10, ranged from 390 to >>1000 kg/ha/year, which are very high values inconsistent with those previously observed (Hortle, 2007). This may be due to the fact that the dataset used to derive the formula included dams characterized by flows much lower than those of mainstream dams. This result indicates that due to their large annual flow volumes, mainstream dam reservoirs appear to fall outside the linear range of this formula. 9.8.2 ESTIMATES OF PRODUCTIVITY BASED ON SURFACE AREA ALONE. By default, the surface area alone is the best single predictor of reservoir productivity. The total production of each mainstream reservoir was estimated using surface areas (Table 9.9) and three productivity levels: low (20 kg/ha/year), medium (50 kg/ha/year), and high (200 kg/ha/year). This large range reflects experience throughout Asia (Sricharoendham et al., 2000; Mattson et al., 2000; Jutagate et al., 2001) and underscores the largely unpredictable nature of reservoir fisheries detailed above. The corresponding estimates for mainstream dam reservoirs, weighed by the shape of the reservoir (deep reservoirs having a low productivity by hectare) are presented in Table 9.12. Conclusions: At best the maximum fish production to be expected from reservoir fisheries amounts to 30,000 tonnes basin wide. In fact when the shape of reservoirs is taken into account, the most likely production represents about 10,000 tonnes for the 1500 km2 of reservoir area created by mainstream dams. This value should be compared with to the 700,000 – 1.4 million tonnes of capture fish production at risk of mainstream dam development (section 5.2.5). Table 9.12: Predicted production range in mainstream dam reservoirs. The most likely production, based on reservoir depth and shape, is highlighted in yellow. The most likely scenario is based on the assumption that reservoirs having more than 50% of their volume comprised between 0 and 2m are very productive (200 kg/ha/year), whereas reservoirs have a medium productivity (50 kg/ha/year) if 20‐50% of their volume is comprised between 0 and 2m, and they are poorly productive (20 kg/ha/year) if less than 20% of their volume lies within the 0‐2m layer. Reservoir Area Average % of total Low Medium High Most likely (km2) depth (m) volume at productivity productivity productivity scenario depth ,2m scenario scenario scenario (tonnes/year) (tonnes/year) (tonnes/year) (tonnes/year) Pak Beng 87.77 3.1 22.94 175.5 438.9 1755.4 438.9 Louang Prabang 62.38 12.9 10.84 124.8 311.9 1247.6 124.8 Xayaburi 50.43 7.4 86.57 100.9 252.2 1008.7 1008.7 Pak Lay 76.65 5.1 19.74 153.3 383.3 1533 153.3 176 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | FISHERIES Sanakham 70.46 53.7 3.29 140.9 352.3 1409.3 140.9 Pakchom 55.76 1.7 78.23 111.5 278.8 1115.2 1115.2 Ban Koum 133.69 4.7 10.8 267.4 668.5 2673.8 267.4 Latsua 13.33 9 19.43 26.7 66.6 266.6 66.6 Don Sahong 2.89 10.6 16.36 5.8 14.4 57.8 5.8 Stung Treng 234.23 6.6 27.62 468.5 1171.2 4684.6 1171.2 Sambor 715.89 4.9 31.3 1431.8 3579.5 14317.9 3579.5 Total 1503.49 3007 7517.5 30069.9 8072.3 9.9 SENSITIVITY ANALYSIS OF DAM GROUPINGS 9.9.1 UPSTREAM CLUSTER OF DAMS CHANGES IN HYDROLOGY Upstream of Vientiane, in 2015 as well as in 2030, discharge will be 40 to 60% higher in the dry season than in 2000. However, most of the change is due to Chinese dams and the additional changes due to Lower Mekong mainstream dams are limited. In the wet season water level will be around 50 cm lower than compared to the baselie (again, no major difference between 2015 and 2030). So from a seasonal perspective, mainstream dams in the upstream cluster will not have a major impact on the hydrology of that area already driven by Chinese and tributary dams. However the daily variability in water levels created by several of these dams operation in peak mode (see table 9.6) might be very substantial, but could not be documented here due to lack of data. EXPECTED LOSSESS WITHOUT MAINSTREAM DAMS This section of the river is characterized by typical stream species living in riffles and fast flowing waters (Balitoridae, Cobitidae, etc; Baseline Assessment section 1.4). In case of the Definite Future scenario (absence of LMB mainstream dams), the increased dry season discharge due to Chinese dams is expected to alter riffles and shallow habitats used by species for breeding and as nurseries. The construction of 17 dams on tributaries in the upstream cluster (‐46,000 km2, see Annex 1) will also reduce fish habitat. As a consequence, a drop in the recruitment of local species is expected even in absence of mainstream dams in the upstream cluster. The contribution of these upstream species to the fish biodiversity of the basin is very important: with 93 species, Balitoridae represent the second most species‐rich family in the Mekong, after Cyprinidae. EXPECTED LOSSESS WITH MAINSTREAM DAMS: The extensive South American experience of extensive damming in large river basins summarised by Quiros (2004) indicates that the loss in capture fish production amounts to at least 50%53. Based on this experience we make below the assumption that losses in capture fisheries could reach 50% in case 6 upstream mainstream dams only are built, 60% if 9 mainstream dams are built (from Pak Beng down to Don Sahong) and 70% if all 11 mainstream dams are built. 53 Quiros indicates that after a decade the fish production drops “well below 50%” of its original state 177 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | FISHERIES POSSIBLE FISH BIODIVERSITY LOSSES: LMB mainstream dams in the upstream cluster will have two main consequences: barrier effect for migrant fish and modification of riverine habitats by creation of reservoirs. The 6 upstream dams would create 403 km2 or 715 linear kilometers of reservoirs, i.e. slow lacustrine, largely deoxygenated and stratified water in lieu of the former running waters (the two deepest reservoirs of the basin, Luang Prabang and Sanakham ‐average depth of 13m and 54m respectively, see Table 9.13‐, would be located in this zone). Table 9.13: Length of reservoir created in the upstream cluster in relation to river length Total length % of mainstream Reservoir length River Dam of reservoirs turned (km) Length (km) (km) into a reservoir Pak Beng 180 Luang Prabang 150 Xayaburi 100 715 795 90 Pak Lay 110 Xanakham 90 Pak Chom 85 According to existing species records (MDF 2003, Dubeau 2004), the zone between Vientiane and the Chinese border includes 189 fish species. Out of these, an analysis of the MRC Mekong Fish Database records shows that at least forty‐one species are not found elsewhere in the LMB (Annex 5). Mainstream dams will trigger a significant change in habitat, but stream species will also be subject to the impact of the other dams on tributaries. One species (Acheilognathus deignani) provides an extreme example of the outlook for some stream fishes in this zone: this species is found in the mainstream and in the Nam Ou only; regardless of plans in the mainstream, in the Nam Ou Basin there are plans for 11 other dams (projects Nam Ou 1 to 7, to be operational between 2013 and 2015, with a height comprised between 47 and 147 m, plus Nam Nga, Nam Phak, Nam Ngao and Nam Pok projects, planned after 2017, 5 ‐ 69 m high). Table 9.14: Catch of migrant white fish vulnerable to mainstream dam development Cambodia Lao PDR Thailand Viet Nam Total Total catch (estimate based on fish 481,537 167,922 720,501 692,118 2,062,077 consumption studies) Yield at risk under the assumption of 168,500 58,800 252,200 242,200 721,700 35% of vulnerable species Yield at risk under the assumption of 337,100 117,500 504,400 484,500 1,443,500 70% of vulnerable species Conclusions: In the upstream migration zone biodiversity is clearly at risk. Following the construction of 6 mainstream dams in this area, 90% of the river stretch between the Chinese border and Vientiane would be turned into a reservoir. At least 41 species are threatened by a severe alteration of their habitat. By comparison this number corresponds for instance to about half the total freshwater fish fauna of the United Kingdom (99 species). The family most exposed would be Balitoridae (river loaches), with about 10% of its 93 178 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | FISHERIES Mekong species at risk. The iconic, endemic and critically endangered Mekong Giant catfish would also be much at risk of total extinction since its main breeding area is located in this area, near Chiang Saen. However since 17 other dams blocking access to 46,000 km2 upstream of tributaries are also planned in the area, habitat alteration and impact on fish biodiversity are not specifically due to mainstream dams. There is no information as to whether any of the 41 species specifically threatened can survive in reservoirs. This estimate is very close to that given by Barlow et al. in 2008 (0.7 – 1.6 million tonnes at risk). Our review integrates two methods used in Barlow et al. (200854) but not the more approximate third one (it is the latter method that provided the upper range of Barlow’s estimate, i.e. 1.57 million tonnes of fish at risk). On the contrary the present review integrates two more approaches based on field data, reflects recent findings about the importance of black fish in catches, is explicit about the amount of white fish and black fish in each method, and integrates error ranges in both percentages of long distance migrant fish and total catch. POSSIBLE FISH PRODUCTION LOSSES (2030, 6 MAINSTREAM DAMS IN THE UPPER LMB): In this upstream cluster zone, the local fish production amounts to 40,000 – 60,000 tonnes per year (Baseline Assessment, section 2.4.2), which represents 2‐3% of the most likely fish production basinwide (i.e. 2.1 million tonnes, Baseline Assessment section 2.1.3) or 3‐5% of the fish production along the mainstream (Baseline Assessment, Table 28). At the local level, in absence of other mainstream dams and based on the assumptions detailed under section 7.1.3. (i.e. 50% losses in capture fisheries), the fish losses in catches of the local fishery would amount to of 20,000 to 30,000 tonnes of capture fish. At the Basin level, in absence of other mainstream dams, but in presence of the other tributary dams planned by 2030, 31% of the Basin will be specifically obstructed by the dams of the upstream cluster (scenario S4 in Table 3). However the 27 fish species will still find habitat for breeding and feeding in the (100‐68.7) = 31.3% of the basin not obstructed by any dams. The analysis detailed in Section 5 shows that at least 27 species of long‐distance migrants representing about 18% of catches basinwide, i.e. around 380,000 tonnes, use this section of the river. When a correction factor is introduced to reflect the importance of black fish in catches basinwide and the real share of long‐distance migrants vulnerable to the barrier effect of dams, i.e. 35‐70% of the overall stock (see Section 5.2.5), the conclusion is that the risk of fish production losses in case the 6 upstream mainstream dams are built amounts to 130,000 – 270,000 tonnes 55 POSSIBLE FISH PRODUCTION GAINS DUE TO DAMS: The mainstream dams of the upstream cluster will create 403 km2 of reservoir. This area can be expected to produce between 800 and 8,000 tonnes of reservoir fish, the most likely estimate being 3,000 tonnes. This production will be supplemented by that from dam reservoirs on tributaries, but there is no information about the cumulative surface area of these projects on tributaries, so their potential reservoir production cannot be precisely assessed. As a crude alternative estimate, one can note that the surface area of exisiting reservoirs in northern Laos and Thailand ranges between 10 and 80 km2 (Bernacsek 1997); if we take 54 in the case of method 1 in Barlow et al.’s paper, two mistakes had to be corrected: i) the estimate of LMB total in Hortle (2007) is actually 2,062,000 tonnes, not 1,860,000 tonnes, and ii) a typo in the result of 1,860,000 x 38.5% 55 [380,000 tonnes x 35%] ‐ [380,000 tonnes x 70%] 179 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | FISHERIES 40km2 as an average, this corresponds to around 700 km2 for the 17 dams planned, and depending on the level of productivity, the corresponding reservoir fish production would range between 1,400 and 14,000 tonnes, which, added to the production of mainstream reservoirs, would represent between 2,000 and 20,000 tonnes of fish, the most likely estimate being around 7,000 tonnes of reservoir fish per year in this zone. Conclusions: In the upstream cluster zone, the fish production represents 5% maximum of the Mekong fish production. In this area covering 123,700 km2 there might be 23 hydropower projects by 2030 56, which means that the river network would be largely obstructed by dams, and that the local habitat of the 189 local fish species will change drastically. Following dam development a loss of fish production and of fish biodiversity is to be expected. At the local level, the loss of capture fish (20,000 – 42,000 tonnes) and the additional production of reservoirs (most probably around 7,000 tonnes) would result in a net loss of 13,000 to 35,000 tonnes of fish supply. This would be a very substantial risk for food securlity, corresponding to 15% to a third of the whole annual meat production of the country57. At the Basin level, the construction of mainstream dams in the upstream cluster would reduce fish production in the whole Mekong Basin by 130,000 – 270,000 tonnes. 9.9.2 MIDDLE CLUSTER OF DAMS CHANGES IN HYDROLOGY In 2015, according to the BDP2, between Vientiane and Pakse, discharge will be one third higher in the dry season than in 2000. These forecasts are roughly in line with those of BDP1 and the WorldBank, but not with those of the Nam Theun 2 project that predicts more than doubling of the flow in the dry season. BDP2 forecasts are almost identical for the other scenarios (2030 with 0, 6, 9 and 11 mainstream dams), with just a few percents variation in wet season discharge compared to the situation forecasted in 2015, i.e. dry season discharge increased by a third compared to 2000. During the monsoon season, according to BDP2, water level will be 30 cm lower in 2015, although there is a discrepancy with other studies that forecast between ‐40cm to ‐1.6 m. For the 2030 scenarios wet season water level is expected to decrease by 40 to 50 cm maximum, whatever the number of dams on the mainstream. 56 Nam Beng (30 MW; 2014), Nam Dong (1 MW; 1970), Nam Ko (2 MW; 1996), Nam Long (5 MW; 2013), Nam Nga (98 MW; 2017), Nam Ngay (1 MW; 2002), Nam Ou 1 (180 MW; 2013), Nam Ou 2 (90 MW; 2014), Nam Ou 3 (300 MW; 2013), Nam Ou 4 (75 MW; 2014), Nam Ou 5 (108 MW; 2013), Nam Ou 6 (210 MW; 2014), Nam Ou 7 (180 MW; 2015), Nam Pha (147 MW; 2016), Nam Suang 1 (40 MW; 2016), Nam Suang 2 (134 MW; 2016), Nam Tha 1 (168 MW; 2013), plus the 6 mainstream projects 57 http://faostat.fao.org/site/610/DesktopDefault.aspx?PageID=610#ancor 180 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | FISHERIES Like in the upstream cluster, the very substantial daily variability in flows to be expected from Latsua dam planned to operate in peak mode (2m daily variability in its reservoir level) could not be detailed nor analysed by lack of data. EXPECTED LOSSESS WITHOUT MAINSTREAM DAMS Given the absence of taxonomic records in the mainstream between the two dam project and Vientiane, it is difficult to identify species that are dependent on the mainstream in this section of the river. In absence of mainstream dams, in 2015 188,000 km2 (23.6% of the LMB) would be barred by dams on tributaries anyway, and in 2030 296,000 km2 of watershed, i.e. 37.3% of the LMB, would be obstructed (see Annex 1). This would represent a loss of 4 and 17% of connectivity compared to the baseline situation in 2000. This loss implies a loss of access to breeding areas upstream of tributaries, and a subsequent loss of productivity to be expected even without mainstream dams. A diversity of other factors detailed in the Baseline Assessment (section 6.2 and Table 43) and unrelated to LMB mainstream dams (e.g.; loss of connectivity in floodplains, increased fishing pressure, etc) will contribute to fish catch reduction. However insufficient knowledge about resilience of fish resources and lack of accuracy in multidimensional forecasting make it impossible to predict the extent of these losses. Another degree of uncertainty is introduced by the management of the Pak Mun dam (6 Km upstream of the confluence with the Mekong River): until 2001 dam gates were permanently closed, then open until 2002, then open 4 months a year until 2007, then they were permanently closed again. The Pak Mun dam controls access to the Mun/Chi sub‐basin (120,000 km2) and blocks migrations between the mainstream and this basin, and its significant impact on fish production has been reviewed in Amornsakchai et al. (2000). According to this study, the closure of the Mun River impacted in particular 17 migratory fish species, including 15 catfish species, whose migration routes were blocked, and whose spawning ground habitats upstream were modified. Jutagate et al. (2001) also found that after Pak Mun dam closure, only 96 fish species remained out of the previous 265 species. EXPECTED LOSSESS WITH MAINSTREAM DAMS: POSSIBLE FISH BIODIVERSITY LOSSES: With the 2 dams of the middle cluster, 165 kilometers of river, i.e. 23% of the mainstream between Pakse and Vientiane, would be turned into a reservoir. This would have a definite impact on biodiversity, although the magnitude of this impact could not be quantified here. Table 9.15: Length of reservoir created in the middle cluster in relation to river length Reservoir length Total length of River length % of mainstream Dam (km) reservoirs (km) (km) turned into a reservoir Ban Koum 155 165 713 23 Lat Sua 10 The Latsua dam, although located only 34 km below the Ban Koum dam, would have much more negative impact on fish migrations and production than the latter because it would block access to the Mun/Chi system (70,000 km2). With 270 species (Baseline Assessment, section 1.4), biodiversity in the Mun/Chi system is very high and this basin is subject to intensive fish migrations. The Latsua dam would have the 181 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | FISHERIES same impact than the Pak Mun dam on Mun‐dependent fish species, plus additional impact on species migrating up the mainstream, and the construction design does not mention sluice gates. Given the absence of taxonomic records in the mainstream between the two dam project and Vientiane, it is difficult to identify species that are dependent on the mainstream in this section of the river. However some species identified thanks to the analysis detailed in Section 5.1 are specifically at risk (Table 9.15). If Ban Koum dam is built, 28 of the long distance migrant species have an alternative in the 3S system (except if Lower Sesan 4 is built) and in the Mun/Chi system (except if the Pak Mun dam is closed). Four species do not migrate towards the 3S system: Boesemania microlepis, Cyclocheilichthys enoplos, Pangasius polyuranodon, Pangasius sanitwongsei; they represent at least 1.7% of the fish production. If Latsua or Stung Treng dams are built, 26 of these species have an alternative in the 3S system (except if Lower Sesan 4 or the 20 other dams considered in these 3 watersheds are built). Table 9.16: Some particular fish species related to the Mun / Chi system Family Scientific Name Information available Species Found only in large rivers of the Middle Mekong Basin. Most closely common along the Thai‐Lao border at the mouth of the Mun associated River; it also used to occur in Mun and Songkhram Rivers, but is with the Mun Cyprinidae Aaptosyax grypus now an extremely rare species / Mekong An uncommon fish in the Mekong. Occurs just upstream from confluence Cyclocheilichthys Khone Falls at the mouth of the Mun River. Also recorded from Cyprinidae heteronema the Great Lake. Distribution: Mekong Basin in Laos and Thailand (mouth of Nam Mystacoleucus Mun) and possibly in Yunnan. Recorded from the Mae Kok at Cyprinidae chilopterus Chiang Rai and Mae Poon In the Mun River, the species migrates upstream from the beginning of the rainy season to the end of August and move back Helicophagus downstream from late September to November. Distribution: Pangasiidae waandersii found basin wide in the mainstream of the Mekong. This species is impacted by the Pak Mun Dam, because it blocks their migration route and the fish pass is not working properly, and the rapid habitats where the fish used to spawn have been inundated by the head pond. Distribution: the northern boundary for this species is at Chiang Saen, however the main distribution range is from Nakhon Phanom to Kandal Province in Cambodia. Pangasiidae Pangasius kunyit Now ery rare in the Mun River Known from the Middle Mekong along the Thai‐Lao border to the Species Tonle Sap. Recorded from the confluence between the Mun and related to the Cyclocheilichthys the Mekong Rivers and from the Mekong at Ban Tha Kai 21 Mun system Cyprinidae furcatus kilometres downstream from Mukdahan. In the Mun River, the species migrates upstream from the beginning of the rainy season to the end of August and move back downstream from late September to November. Occurs from Chiang Saen to Pak Lay, however from Chiang Khan to Paksan the species was not reported. Occurs again at Thakho and Mekongina downstream to Sambor. Also recorded from Xe Bangfai, Nam Cyprinidae erythrospila Theun, and Chi Rivers. May spawn in the delta or mouth of the Mekong; other spawning Pangasianodon grounds have been identified in the mainstream of the Mekong Pangasiidae gigas River near Chiang Rai, and in the Mun River at Ubon Ratchathani. 182 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | FISHERIES An important spawning ground appears to be in the Mekong mainstream somewhere between Kampong Cham and Khone Falls and in rapids and riffles of the Mun river . Distribution: the Pangasius distribution range is from the Mekong Delta all the way along the Pangasiidae conchophilus Mekong to Chiang Saen. Source: MFD 2003 POSSIBLE FISH PRODUCTION LOSSES (2030, 9 DAMS, NO CAMBODIAN MAINSTREAM DAMS): Under this scenario 78% of the Basin would not be accessible to migrant fish coming from downstream floodplains, and 41% of the Basin would be specifically obstructed by mainstream dams (Annex 1). Overall, 41 species are known to migrate though Khone Fall on their way to the upstream part of the LMB (Annex 4). These species represent 28.5% of the overall catch (2.1 million tonnes), i.e. about 600,000 tonnes. When a correction factor is introduced to reflect the importance of black fish in catches basinwide and the real share of long‐distance migrants vulnerable to the barrier effect of dams, i.e. 35 to 70% of the overall stock (see Section 5.2.5), the conclusion is that the risk of capture fish production losses in case the 2 mainstream dams of the middle cluster are built amounts to 210,000 – 420,000 tonnes 58. This approach leads to an estimate much lower than that detailed in Section 5.2.5; thatissue is detailed in Section 7.3.3. POSSIBLE FISH PRODUCTION GAINS DUE TO DAMS: The Ban Koum and Latsua mainstream dams would create 147 km2 of reservoir. This area can be expected to produce between 300 and 3,000 tonnes of reservoir fish, the most likely estimate being 330 tonnes. This production will be supplemented by that from the 77 dam reservoirs on tributaries, but there is no information about the cumulative surface area of these projects on tributaries, so their potential reservoir production cannot be precisely assessed. As a crude alternative estimate, one can note that the average surface area of the 36 LMB reservoirs listed in Bernacsek (1997) amounts to 143 km2. For 77 dams, the cumulated surface area would be 11,024 km2. Depending on the level of productivity, the corresponding reservoir fish production would range between 22,000 and 220,000 tonnes, the most likely estimate being 55,000 tonnes. Conclusions: The Latsua dam would have much more negative impact on fish migrations and production than the Ban Koum dam because if would block access to the Mun/Chi system. It would then reiterate the impacts of the Pak Mun dam on the Mun River, in addition to those on the mainstream. Under this scenario 78% of the Basin would not be accessible to migrant fish coming from downstream floodplains. The risk of capture fish production losses in case the 2 mainstream dams of the middle cluster are built amounts to 210,000 – 420,000 tonnes (probably an underestimate). However the overall production or fish in reservoirs basinwide can be expected to reach 55,000 tonnes. This would result in a net balance of 155,000 – 365,000 tonnes of fish production lost in case the Ban Koum and/or Latsua dams are built. 9.10 DOWNSTREAM CLUSTER OF DAMS CHANGES IN HYDROLOGY 58 [600,000 tonnes x 35%] ‐ [600,000 tonnes x 70%] 183 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | FISHERIES In 2015, according to the BDP2, in the downstream migration zone of the LMB, from Pakse down to the sea, the dry season discharge would be 13 to 22% higher than in 2000. Like in other comparisons, these results are similar to those of the WorldBank and BDP1 forecasts, but much lower than the Nam Theun 2 predictions (+125%). In the wet season in 2015, average water level would be around 30 cm lower than in 2000. In terms o f discharge or water level, BDP2 forecasts are almost identical for the other scenarios (2030 with 0, 6, 9 and 11 mainstream dams), with just a few percents variation compared to the situation forecasted in 2015. In terms of changes in floodplains, when compared to 2000, BDP2 predicts a loss of 250,000 ha of floodplains in the whole Basin by 2015 and a loss of 309,000 ha of floodplains by 2030 (‐5 and ‐7% respectively). It is not clear whether this forecast integrates the notion of double ring (detailed in section 3) due to the increase of 30cm of water level in the dry season. Additional forecasts include, for the Tonle Sap area, a reduction of flood duration by 2 weeks to 1 month and a reduction of sediment inflow in the system of at least 8 to 13%. EXPECTED LOSSESS WITHOUT MAINSTREAM DAMS The factors that apply to the downstream cluster of dams are the same as those detailed in section 7.2.2: ‐ in absence of mainstream dams, in 2015 188,000 km2 (23.6% of the LMB) would be barred by tributary dams; in 2030 296,000 km2 i.e. 37.3% of the LMB, would also be obstructed by dams on tributaries (see Annex 1). This loss of 4 and 17% of connectivity compared to the baseline situation in 2000 implies a loss of natural fish productivity even without mainstream dams. ‐ multiple factors detailed and unrelated to LMB mainstream dams (e.g.; loss of connectivity in floodplains, increased fishing pressure, agricultural development in the Tonle Sap and subsequent pesticide inputs, reduced sediment inflow due to 77 tributary dams modifying productivity of the estuarine and coastal zone, etc) will contribute to fish catch reduction. However the complexity and interactions between these issues make prediction of losses in capture production losses impossible. The fact that 250,000 ha of floodplains will be lost by 2015 is a third main factor influencing fish production even in absence of mainstream dams. This loss corresponds to a loss of capture fish production comprised between 13,000 and 50,000 tonnes59 (see Section 4). EXPECTED LOSSESS WITH MAINSTREAM DAMS: POSSIBLE FISH BIODIVERSITY LOSSES: The Baseline Assessment (section 1.4) has shown that 204 species are found in the mainstream at the level of Kratie, and 168 species are found below of Khone Falls. Out of these, the analysis of migration patterns described in the Mekong Fish Database (Annex 4) has identified 43 species undertaking long‐distance migrations through the mainstream. It is clear that a number of additional species would be impacted by the transformation, between Kratie and Pakse, of 42% of the mainstream into reservoirs, but the exact number of species at risk could not be specified during this study. 59 [250,000 x 50 kg/ha/y] – [250,000 x 200 kg/ha/y] 184 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | FISHERIES Table 9.17: Length of reservoir created in the downstream cluster in relation to river length Dam Reservoir length Total length of River length % of mainstream (km) reservoirs (km) (km) turned into a reservoir Don Sahong 5 Stung Treng 45 140 330 42 Sambor 90 Overall, the analysis of tables 9.13, 9.14 and 9.16 shows that if 11 reservoirs are built, 55% of the mainstream will be turned into a dam reservoir. If Cambodian dams are not built, “only” 48% of the mainstream would be turned into a lake. Table 9.18: Linear length of reservoirs and total length of the mainstream Total length of reservoirs (km) 1020 River length (km) 1838 % of mainstream turned into a reservoir 55 POSSIBLE FISH PRODUCTION LOSSES (2030, 11 MAINSTREAM DAMS): following this scenario 81.3% of the Basin river network and fish migration routes would be obstructed by dams, 44% of this obstruction being due specifically to mainstream dams Overall, 43 species are known to migrate between downstream floodplains where they feed and upstream habitats where they breed (Annex 4). These species represent 29.8% of the overall catch, i.e. about 630,000 tonnes. When a correction factor is introduced to reflect the importance of black fish in catches basinwide and the real share of long‐distance migrants vulnerable to the barrier effect of dams, i.e. 35 to 70% of the overall stock (see Section 5.2.5), the conclusion is that the risk of fish production losses in case the 2 mainstream dams of the downstream cluster are built amounts to 220,000 – 440,000 tonnes 60. This approach leads to an estimate much lower than that detailed in Section 5.2.5. In the latter the specific impact of a subset of dams is not detailed, but the overall conclusion is that if 81% of the LMB are obstructed by dams (cf. Annex 1), then 700,000 to 1.4 million tonnes would be at risk. The difference between these two assessments can be explained by the fact that the latter refers to all dams of the LMB (scenario 2030, 11 mainstram dams) whereas the former refers oly to the specific impact of the dams of the middle cluster. Another factor is the loss of floodplain area. This loss involves all species using the floodplains, and not only migrant white fish. Therefore this loss is to be added to the above loss. BDP2 estimates that 309,000 – 251,000 = 58,000 ha of floodplain would be lost in case of mainsream dam development (the 251,000 ha being lost even in absence of mainstream dams; see Table 9.5). This loss of floodplains corresponds (see Section 4) to 3,000 to 12,000 tonnes of fish61. POSSIBLE FISH PRODUCTION GAINS DUE TO DAMS: The Stung Treng and Sambor mainstream dams would create 950 km2 of reservoir. This area can be expected to produce between 2000 and 19,000 tonnes of reservoir fish, the most likely estimate being 47,000 tonnes. This production will be 60 [630,000 tonnes x 35%] ‐ [630,000 tonnes x 70%] 61 [58,000 ha x 50 kg.ha/year = 2900 tonnes] – [58,000 ha x 200 kg.ha/year = 11,600 tonnes] 185 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | FISHERIES supplemented by that from the 77 dam reservoirs on tributaries, but there is no information about the cumulative surface area of these projects on tributaries, so their potential reservoir production cannot be precisely assessed. Like in section 7.2.4, one can note that the average surface area of the 36 LMB reservoirs listed in Bernacsek (1997) amounts to 143 km2. For 77 dams, the cumulated surface area would be 11,024 km2. Depending on the level of productivity, the corresponding reservoir fish production would range between 22,000 and 220,000 tonnes, the most likely estimate being 55,000 tonnes, to be supplemented by the 2,000 – 19,000 tonnes from the two dams of the downstream cluster. If all mainstream dams are taken into account, then the overall reservoir fish production would be: • from tributary dams: 22,000 – 55,000 – 220,000 tonnes (see above) • from mainstream dams: 3,000 – 8,000 – 30,000 tonnes resulting in a range comprised between 25,000 and 250,000 tonnes, the most likely production being 63,000 tonnes. Conclusions: Due to the presence by 2030 of 77 tributary dams in the basin, resulting in 37% of the fish migration routes obstructed and at least 250,000 ha of floodplains lost, losses in capture fish production will be high even in absence of mainstream dams; however they cannot be quantified. In presence of mainstream dams in the downstream cluster (between Pakse and Kratie), 55% of the length of the mainstream would be turned into a reservoir. This would have profound impacts on biodiversity, in particular on 43 species having to undertake long‐distance migrations and making up to 220,000 to 440,000 tonnes of fish in the downstream migration zone of the Lower Mekong Basin. An alternative estimate amounts the possible loss for the overall basin to 700,000 to 1.4 million tonnes. An additional 3,000 to 12,000 tonnes of capture fish losses would follow the reduced surface area of floodplains resulting form the constuction of mainstream dams. These losses could be partly compensated by the production of reservoir fish. The total amount of reservoir fish produce would range between 25,000 and 250,000 tonnes, the most likely scenario being 63,000 tonnes. 186 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | SOCIAL SYSTEMS 10 SOCIAL SYSTEMS 10.1 STRATEGIC ISSUES • Poverty and Natural Resource Based Livelihoods • Health and Nutrition • Resettlement 10.2 SUMMARY OF PAST & FUTURE TRENDS WITHOUT LMB MAINSTREAM HYDROPOWER Major land cover transformations have already occurred in all countries in many parts of the Lower Mekong Basin (LMB) over the past 30 years or so. The nature and extent of these transformations are both natural and man‐made. Combined pressure on Mekong communities has been observed from many different directions, whether these pressures are policy, environmental or local unsustainable resource use practices. Natural factors including flooding, drought, and increased saline intrusion (particularly in the Mekong delta). Man‐made factors include changes in agricultural practices, urban growth, land conversion (including infrastructure development, poor fishing practices, urban and agricultural waste discharges into the river, riverbank erosion from soil removal from wetlands for biofertiliser, or sand and gravel from river banks and delta), and destruction of forests and mangroves. Such activities to date have had both positive and negative impacts on the socio‐economy and future food security of LMB populations, with associated consequences for key issues identified under the Social Component theme. 10.2.1 POVERTY REDUCTION Past and current trends in the LMB demonstrate progress towards meeting MDG poverty alleviation targets on some indicators but regression on others. Progress is variable from one LMB country to another, depending on how national strategies are developed and applied. For example, the target to cut the under‐5 mortality rate by 2/3rds between 1990 and 2015 is likely to be met, while targets related to environmental sustainability will not only not be met but become worse, particularly in relation to loss of forest cover, water supply and sanitation62. As there is high livelihood dependence in all LMB countries on water and land resources ‐ the highest in Laos, the lowest in Thailand – the current rapid depletion rate of the natural resource base remains a serious concern for future efforts towards poverty alleviation. The normal livelihood base is one which diversifies both seasonally and occupationally. Increasingly, options for traditional diversification are becoming more limited. The most vulnerable are those with limited coping mechanisms and low 62 "Development Asia: Special Report, Millenium Development Goals", Asian Development Bank, Year II, No. V, October‐December 2009 187 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | SOCIAL SYSTEMS occupational or income source diversity. The shift to alternative livelihoods less rural and less dependent on natural resources takes time, with some households adjusting more successfully than others. Thailand has demonstrated greater movement than other countries in this respect, but it has been achieved gradually over many years and more markedly in some provinces than in others. National revenues from hydropower in the region are increasing, but their association with poverty alleviation remains to be clarified. 10.2.2 HEALTH & NUTRITION The status of these issues in the LMB is directly associated with (i) ease of access to adequate health infrastructure and personnel; (ii) drainage and clean water resource management with its associated health and sanitation consequences; (iii) knowledge and awareness levels, which may be associated with relative vulnerability to food insecurity; and (iv) access to free sources of high nutritional value from natural resources, such as fish, non‐timber forest products, and wild game. Stunting and wasting are characteristics of malnutrition more common in Lao PDR and Cambodia than in Thailand and Vietnam, affecting both life expectancy as well as children's health – each important measures of food security and quality of life, and significantly affecting a country's ability to be economically productive. Public expenditure on health in all LMB countries is uneven, and while Thailand has removed clean water supply and sanitation from its MDG targets (having achieved this by 2007), remaining LMB countries retain the target and have some way to go before achieving it. Some health and nutrition issues can be addressed by improved financial resource allocation, but others are associated with ease of access to the natural resource base. 10.2.3 RESETTLEMENT Numerous gaps remain in land acquisition and compensation policy and procedure compared to international best practice for all LMB countries. Lack of consistent national or transboundary mitigation frameworks present challenges to achieving policy equity in project implementation, while limited human capacity and/or political will to effectively monitor developers and require them to satisfactorily meet policy commitments, remain obstacles to socially equitable resettlement practice. Other land expropriation practices in the LMB such as village resettlement for administrative consolidation, land conversion and urban growth, coupled with unsustainable land and river usage, are already causing communities to lose much of the natural resource base on which their livelihoods depend. This introduces a potential "double jeopardy" context whereby communities affected by one impact may become even more vulnerable when affected by another. All LMB countries agree that the social and political economy of resettlement in relation to hydropower is one of the most serious strategic transboundary issues facing hydropower development in the area. 10.3 EXPECTED DIRECT EFFECTS OF THE PROPOSED LMB MAINSTREAM HYDRO PROJECTS While there is an argument that hydropower projects can contribute to poverty alleviation and achievement of MDGs, impacts also risk contributing to poverty augmentation and failure to meet national poverty reduction goals. This is particularly an issue if suitable mitigation measures are not 188 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | SOCIAL SYSTEMS applied, if developers do not observe mandatory requirements, and if satisfactory land acquisition, compensation and livelihood restoration processes are not undertaken. For example, increased hydropower revenues may be directed towards poverty alleviation strategies within country and help reach MDG targets such as combating malaria and other diseases, or reduce the number of people without clean drinking water or sanitation. On the other hand, direct hydropower project impacts such as livelihood loss due to land acquisition and change in access to customary natural resources, or changes in groundwater flows leading to increased waterlogging with associated domestic water quality and sanitation difficulties, could set back other positive steps towards poverty reduction and towards national efforts to reach MDG goals. Many direct social impacts will be the same for all projects, irrespective of location, but may be of differing intensities on different parts of the river system. All proposed hydropower projects will require land acquisition for construction sites, associated facilities (such as access roads, contractor's camps, etc.) and headponds, which will involve asset loss and relocation of households. Table 10.1 lists the potential number of villages, individuals and households that could experience impacts through land and asset loss directly attributable to individual hydropower projects. Specific asset loss is permanent, temporary and seasonal, and will affect different people under different hydropower projects. These are more fully listed in Annex B. Asset loss due to land acquisition in the construction site as well as inundated land in head pond areas includes: • permanent loss of home and non‐agricultural land • permanent loss of agricultural land (both paddy & swidden) and productive trees (e.g. timber and fruit) • permanent loss of cultural and historical sites and resources (e.g. temples, cemetery) • permanent loss of community resources (e.g. schools, government buildings) • permanent loss of district/community infrastructure (e.g. roads and access tracks) • permanent loss of access to forest resources • permanent loss of accessible grazing land • loss of livelihood drawn from combination of existing natural resources (i.e. integrated household economy consisting of settled agriculture, swidden agriculture, livestock, non‐timber forest products (NTFPs), fisheries) • risk of further impoverishing communities who have already been affected by relocation prior to any Mekong hydropower project (e.g. • seasonal loss of land (e.g. riverbank garden) • seasonal loss of assets (e.g. irrigation pump on the river) • seasonal loss of fisheries Figures of directly affected people in Table 10.1 are conservative, based on the assumption that developers will choose least‐impact technical options and hydropower designs. Overall figures of total affected persons and villages are under‐estimates at the time of this report, as final Social Impact Assessments (SIAs) or Resettlement Action Plans (RAPs) were not made available to the SEA team. No figures were available for Thakho nor for affected people on the Thai side of the Mekong for Pakbeng. Current estimates of persons requiring physical relocation amount to more than 63,000 people from 131 villages. However, more than 107,000 people from more than 203 villages will additionally be directly affected through loss of land, assets, and livelihood resources (excluding fisheries, which are separately estimated in the SEA). Figures of total affected people include both those who will experience relocation as well as those experiencing loss of assets and/or access to resources, thus affecting their overall livelihoods. 189 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | SOCIAL SYSTEMS Table 10.1: Number of villages, households and persons potentially experiencing direct project impacts Total Total Affected Number of Number of 1994 estimates Total Affected Number of Affected Households Resettled Resettled of persons Persons Resettled HHs No. Dam Name Villages (HHs) Villages Persons displaced§ 1 Pakbeng 57 6,831 35,365 28 774 6,700 1,670 2 Louang Prabang 36 2,516 12,966 36 2516 12,966 6,580 3 Xayaboury 29 1,988 4,378 10 391 2,130 1,720 4Pak Lay 27 1,079 19,046 16 NA 6,129 11,780 5 Sanakham* 20 800 4,000 10 800 4,000 12,950 6Pak Chom 2 107 535 2 107 535 NA 7Ban Koum* 7 330 2,570 4 186 935 2,570 8Lat Sua 0 NA NA 0 NA NA NA 9Don Sahong* 4 14 66 4 14 66 66 10 Thakho NA NA NA NA NA NA NA 11 Stung Treng* 21 2,059 9160 21 2,059 10,617 9,160 12 Sambor NA 1020 19034 NA NA 19034 5,120 Preliminary Totals 203 16744 107120 131 6,847 63112 51616 Data Sources: NA=Not Available. § report by Compagnie Nationale du Rhone, Acres International Ltd. & Mekong Secretariat Study Team, 1994 * indicates figures from 1994 study, no updated information available to SEA 1. Data from Initial Environmental Examination (IEE), Pak Beng Hydropower Project, Lao PDR , December 2008, Earthsystems, Norconsult & SEA Inception Report Vol 2 Project Profiles 2. SEA Inception Report, Vol. 2, Project Profiles 3. Final Report, Social Impact Assessment of Xayabouri Hydroelectric Power Project, Lao PDR, August 2008, Team Consulting Engineering & Management Co. Ltd., Ch.Karnchang Public Company Ltd. & SEA Inception Report, Vol. 2, Project Profiles 4. Initial Environmental Examination (IEE), Pak Lay Hydropower Project, Lao PDR, June 2008, Earthsystems, Norconsult, CEIEC & Sinohydro Joint Venture. Figures taken are for the maximum impacts downstream option. The upstream site would affect more than 2/3rds less households. 12. SEA Inception Report, Vol. 2, Project Profiles Both direct and indirect impacts will be experienced in different stages. The first direct impacts will be felt during the construction phase. These will include land acquisition for: 1. dam site 2. access roads 3. transmission lines 4. contractors camps 5. spoil areas Second will be the impoundment phase, where direct upstream impacts will include: 1. land and riverbank gardens inundated 2. groundwater levels elevated 3. aquatic resources affected 4. livelihoods de‐constructed 5. potential for uncontrolled immigration of outsiders 6. loss of submerged cultural heritage and community assets The third and final phase where impacts will be experienced is during the operational period. These mainly affect downstream areas once dam testing and operations begin. Impacts will be both direct and indirect. Direct downstream impacts include: 190 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | SOCIAL SYSTEMS • seasonal loss of riverbank gardens • permanently altered livelihood options (such as local transport, mainstream fishing) due to altered river flows • potential loss of nutritional and commercially valuable aquatic plants due to increased water turbidity • potential erosion risk to riverbank structures (e.g. temples) located in close proximity to existing riverbanks • affecting irrigation pumps located on the river through fluctuations in downstream flows • restricted cross‐river access due to higher water levels in dry seasons and increased flows • possible decreased downstream water quality, particularly in early years of operation • fisheries will also be affected, both in terms of quantity and variety of species available and in excluding some fisheries sites due to faster running water ‐ this topic is dealt with separately in the SEA. The MRC has defined 6 LMB hydro‐ecological zones as shown in Map 1, which also shows relative poverty rates in each zone. Zones are described in Table 10.2, as are locations of the 12 proposed mainstream dams which are the subject of this SEA. Table 10.2: Hydro‐ecological zoning of the Lower Mekong Basin and location of proposed Mekong mainstream hydropower projects Proposed Hydropower Zone Location Project Total No. Dams 1 China – Chiang Saen Chinese dams 3 operational 1 in construction 4 proposed 2 Chiang Saen ‐ Vientiane Pak Beng Louang Prabang Xayaburi 6 Pak Lay Xanakham Pak Chom 3 Vientiane ‐ Pakse Ban Koum Latsua 2 4 Pakse ‐ Kratie Don Sahong Thakho Stung Treng 4 Sambor 5 Kratie – Phnom Penh & Tonle Sap 0 6 Phnom Penh – Mekong delta & sea 0 10.4 EXPECTED INDIRECT EFFECTS Some indirect impacts may be more location‐specific and may take longer to materialise, particularly with respect to some health and resettlement factors. For example, the northern cluster of Pak Beng, Luang Prabang, Xayaburi, Pak Lay, Xanakham and Pak Chom (Zone 2) are in quite mountainous areas with steeply sided elevations. Numbers of directly affected people for these 6 dams are already high (Table 10.1). Reviews of the Manwan dam on the Chinese section of the upper LMB63 indicate that slope 63 He Daming, Zhao Wenjuan, Chen Lihui, "The Ecological Changes in Manwan Reservoir Area and Its Causes", Proceedings abstract, International Conference on Advances in Integrated Mekong River Management, 25‐27th October 2004, RR2 Research Group & Mekong River Commission; Yu Xiaogang, Jia Jiguo, "An Overview of Participatory Impact Assessment for Manwan Hydropower Station in Lancang River", no date 191 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | SOCIAL SYSTEMS erosion through additional land clearance, rapid changes in filling and releasing reservoir flows, and development of associated facilities for the dam such as roads and irrigation works, have resulted in unanticipated landslides and mudflows, soil and water loss, and frequent torrential flooding. This has required additional relocation of some 1,000 people at extra cost, and leaving a further 8 townships under threat. Because cultivable arable land in the Lao and Thai sections of Zone 2 is very scarce, replacement land will be difficult to identify. Affected communities, or neighbouring communities, in areas of the 6 upper LMB cascade of dams may clear land on steeper slopes for swidden cultivation, further contributing to risks of erosion with subsequent direct impacts on their own villages as well as on others in the area. Many riparian districts in these locations have a high percentage of their land above a 16% slope. All Lao riparian districts in Zone 2 with the exception of Kenthao and Vientiane, have between 26%‐50% of fragile land slope. Five riparian districts falling into impact areas (Paktha, Pakbeng, Nga, Hongsa, Nan and Chomphet) have an even higher percentage (51%‐75%) of steep land as a percentage of the total district land area64. Watershed protection and slope stabilisation in this Zone will therefore be essential to avert unplanned impacts later in the project cycle. Indirect impacts may also include: • cumulative impacts (e.g. long‐term effects such as changes in groundwater flows) • consequences resulting from opportunities which would not have existed without dams (e.g. improved trans‐Mekong access with associated improved marketing links as well as human trafficking opportunities), and • transboundary watershed effects 64 Map 8, Districts with Fragile Lands, "District Vulnerability Assessment: Lao PDR", United Nations, World Food Programme, February 2010 192 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | SOCIAL SYSTEMS Map 10.1: Hydro‐ecological zones of the Lower Mekong Basin and their poverty rates Source: Mekong River Commission, "Integrated Basin Flow Management Progress Report (IBFM)", 2007 193 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | SOCIAL SYSTEMS As land flattens out on the Mekong mainstream, other area‐specific indirect impacts may be associated with dams further downstream, particularly in Zones 4 and 5 (Don Sahong, Thakho, Stung Treng, Sambor). As the baseline indicated, health issues related to vector borne diseases, poor water management and sanitation, and higher levels of poverty‐related symptoms such as wasting and stunting, are more evident in provinces and districts further downstream, particularly in southern Laos and Cambodia (Maps 2 and 3). In Laos, all Zone 4 riparian districts have at least 61%‐80% of households with poor sanitation, while 3 districts (Pakse, Soukhouma and Mounlapamok) show an even worse situation with between 81%‐90% with poor sanitation65. Any changes in groundwater elevations and flows may result in increased waterlogging, with a likely increase in already serious water and sanitation‐related health problems in these areas. All reports on LMB food security acknowledge that rice sufficiency, either through cultivating oneself or by having enough money from other sources to buy it, is a primary way in which communities define food security, which in turn depends on seasonal factors. The FAO notes that the main causes of malnutrition in Cambodia include low food intake and chronic illness, caused primarily by household food insecurity, and lack of clean water and sanitation66. Lack of access to land in Cambodia is a critical factor contributing to poverty levels, not just in relation to individual ownership and use, but to commons also. Map 3 shows that both Kratie and Stung Treng, provinces affected by proposed construction of 2 dams and downstream impacts of 2 more, have among the highest poverty rates in the country at more than 45% of the population. Impacts from land loss and potential increased risk of disease may be considered more serious in these Zones. The WFP also observes67 that man‐made factors have become increasingly important in presenting serious risks to sustainable economic growth and improved food security in Cambodia. These factors include: rapidly increasing population, decreasing access to land, weak institutional capacity, poor infrastructure, social exclusion and increasingly uneven distribution of wealth. These key points were also observed by stakeholders during SEA discussions for all countries, and were not confined to Cambodia alone. While district poverty levels in Thailand and Vietnam are generally lower than in Laos and Cambodia (Maps 4 and 5), the highest proportion of poor and vulnerable households in Thailand are clustered in riparian districts in Zones 3 and 4. Mekong delta districts are better off than in other parts of Vietnam, but high population concentrations mean that actual numbers of poor and vulnerable households may be similar to other LMB countries. Arsenic in groundwater is a natural phenomenon in Zones 5 and 6 in Cambodia and Vietnam. Any changes to groundwater flows or increase in waterlogging due to dams in the lower part of the Mekong river (Stung Treng, Sambor), bring risks of increased incidence of health issues related to wider distribution of arsenic‐contaminated groundwater. 65 Map 9, Households with Inappropriate Sanitation, ibid 66 FAO, Nutrition Country Profiles, Cambodia, 1999 67 p. 16, "Integrated Food Security and Humanitarian Phase Classification (IPC), Pilot in Cambodia, Final Report", World Food Programme, April 2007. 194 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | SOCIAL SYSTEMS Map 10.2: Percentage of People below the Poverty Line, by district, Lao PDR 195 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | SOCIAL SYSTEMS Map 10.3: Poverty Rates in Cambodia 196 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | SOCIAL SYSTEMS Map 10.4: Vulnerability Analysis by district, Thailand Map 10.5: Poverty rates by district, Vietnam To be inserted 197 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | SOCIAL SYSTEMS 10.5 OVERALL ADVANTAGES AND RISKS Overall advantages and risks associated with mainstream hydropower development and identified by different stakeholders during the course of the SEA, are outlined in Table 10.3. There is no weight given to any point. The relative importance of each impact is difficult to quantify, with each sector and each country considering its own priorities and concerns as the most important, while viewing impacts of other sectors or countries not important enough to constitute an insuperable objection to construction of a particular project. Achieving equitable socio‐economic tradeoffs may prove impossible. For example, does agriculture count as much as industry as a livelihood option? Do poverty risks to directly affected people outweigh national poverty alleviation opportunities through increased hydropower revenues? Are severe fisheries losses in one country with consequent livelihood impacts on a large number of people justified by national development aims of another country? Achieving a desirable balance is a difficult process, further complicated by competition between different drivers of progress and different interests. Almost all direct impacts listed are permanent and irreversible. However, they can be also be averted or minimised either by changes in technical design, and/or by properly financed, well planned and early implemented social, environmental, resettlement, health and livelihood programmes in line with international standards. Poorly planned and executed projects, with long transitional phases, or where the developer refuses to provide sufficient budgets to meet direct and indirect impacts over a longer period of time, or where the wrong people are made responsible for social and environmental programmes, can wipe out local socio‐economic systems, leaving people without comparable and acceptable alternatives. Poor planning is exemplified by developers with high resistance to any non‐construction expenditure deemed unnecessary prior to revenue generation by which time it is often too late or becomes more expensive to address impacts. Failure to address these issues is extremely high risk for all LMB countries. While it is always difficult to define the context of such risks accurately, many are well known, and where impacts are transboundary, these will be proportionately elevated to a higher level. Five of the twelve proposed dam developers responded to the SEA team's request to provide indications of their Social and Environmental (S&E) component budgets. No breakdown of budgets against specific activities was requested or provided. Results are shown in Table 10.4. 198 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | SOCIAL SYSTEMS Table 10.3: Social Theme: Advantages and Risks of Hydropower Development No. ADVANTAGES RISKS Poverty Reduction Revenue benefits not equably shared, leading to higher costs for agencies dealing with associated impacts (e.g. health agencies having to pay for public health consequences, forestry 1 National revenue generation which can be used to develop other sectors agencies dealing with increase in logging & poaching activities) Those directly affected may not include those benefiting from national poverty alleviation strategies ‐ assumption that the developer will address poverty alleviation of affected people is 2 Transport infrastructure improved, augmenting regional road communications networks not always reliable Public infrastructure improved and associated training provided (e.g. health stations and 3 health personnel) Developer refusing to pay high costs of impact alleviation Projects approved without proper SIAs conducted, under‐estimate of affected people, and 4 Market access improved with trans‐river bridges failure to allocate sufficient finances to address impacts Electricity generation supporting long‐term local and national social and economic Loss of established land‐ and river‐based natural resources, including common property 5 development (schools, hospitals, mining, local value‐adding industries) resources Decreased national energy vulnerability, particularly in the face of rising demand which 6 renewable sources cannot meet Replacement land of equal size and productivity unavailable Alternative work and service provision opportunities for local people during construction Loss of livelihoods, leading to increased food insecurity and landlessness, poorer living 7 period conditions and homelessness Loss of homes, property, community infrastructure, or buildings/locations of cultural, historical 8 Cheaper national price of electricity or spiritual significance Project‐related work opportunities temporary. Little opportunity for skills development, as 9 Higher groundwater levels could facilitate pumped irrigation skilled work reserved for outside labour 10 Facilitates inland transport Electricity supply may not be available to affected people 11 Lower operational costs and maintenance than other energy sources Private river‐based irrigation pumps damaged by rapidly fluctuating water levels Loss of transport‐related livelihoods for those with small boats unable to cope with changed 12 Flood mitigation and control water levels and water flows Pace and intensity of economic investment and provincial development increasing faster than 13 Ensuring greater voltage stability government capacities to deal with it on a number of fronts 199 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | SOCIAL SYSTEMS g g g y g p Health & Nutrition Impact mitigation measures properly implemented can lead to improved living standards, Increased morbidity & mortality through increased vector‐borne disease, transmission of STDs & 1 improved sanitation, reduction of chronic health problems HIV/AIDS via construction workers and increased number of sex workers Loss of fisheries with associated impacts on livelihoods and protein intake, leading to higher 2 Upstream dams affecting fisheries less than downstream dams incidence of stunting and wasting Higher groundwater levels and/or changes in groundwater flows, leading to waterlogging with potential impacts on sanitation‐related health, increased risk of vector diseases, property 3 damage and effects on crops 4 Poorer water quality, with consequences on fish loss, livelihood and health impacts Changes in water flows leading to unexpected flooding and consequent risk of loss of life, 5 property and land Resettlement Benefits‐grabbing by stronger groups, leading to marginalisation of weaker groups ‐ high risks of 1 Infrastructure improvements in resettlement areas "boom and bust" 2 Improved access to infrastructure, including health facilities, markets, etc. Restricts traditional access to land‐based resources with no viable alternatives offered Poor resettlement process leading to break‐up of social and family networks, with added loss of 3 social and cultural capital Associated infrastructure improvement (e.g. roads) can result in opening up previously isolated areas, leading to land‐grabbing, increase in illegal logging, mining, wildlife poaching, and people‐ 4 trafficking from remote villages Operational impacts of dams often difficult to fully anticipate, identify, quantify or mitigate, 5 particularly downstream Time needed for planning, constructing and filling reservoirs can discourage investment in the 6 area and cause losses to area residents Upstream erosion from inadequate watershed protection leading to landslips, causing post‐ 7 resettlement loss of property and requiring additional community relocation and livelihood loss 8 Transboundary costs of watershed protection ‐ rights and responsibilities unclear Difficulty of identifying what is a national and what is a transboundary issue, and related 9 financial consequences 10 Loss of cultural and spiritual assets and location‐specific associations Scarcity of paddy land making land‐for‐land options unlikely to find replacement land of 11 comparable productive and economic value 12 Downstream erosion causing loss of riverbank gardens Lega l and institutional frameworks for social safeguards, and monitoring capacity, poorly 13 understood (particularly at provincial and district levels) and legislation inadequately linked to Governments unclear how to support prior notification process of MRC to facilitate different 14 national decision‐making 200 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | SOCIAL SYSTEMS Table 10.4: Budget allocations for social & environmental compensation and mitigation measures Total Affected People Total Budget Allocated Proposed Dam (including those relocated) (US$ millions) Louang Prabang 12,966 9.88 Pak Chom 535 20 Ban Koum 2,570 35 Thakho Not available 2.18 Sambor 19,034 101.57 Source: SEA Inception Report, Vol. 2, Mainstream Project Profile Summaries Figures of affected people in Table 10.4 remain preliminary. Numbers may increase or decrease, depending on additional information provided later. For example, Pak Chom and Louang Prabang and Sambor have provided estimated numbers of persons relocated only, not of all people directly affected. Thakho has not provided any details on numbers of affected people. We do not know, therefore, the basis of calculating the cost of implementing mitigation measures or of instituting remedial development programmes. Nonetheless, as budget allocations suggest, different developers have widely different views as to the financial costs of land acquisition and compensation, social and environmental mitigation measures required, and of the average allocated amount per affected person. 10.6 POPULATION Population details provide a sense of potential scope of indirect impacts on people in the LMB. Indirect impacts affect a higher number of people than direct impacts. Feedback from the 12 hydropower developers mainly provided numbers of people and villages experiencing actual resettlement, therefore assessment of the number of persons indirectly impacted are somewhat speculative without more in‐ depth study of particular dams. The total population of the LMB is shown in Table 10.5. Vietnam has the highest national population, while Thailand has the highest LMB population. However, although Laos has the lowest number of people both in national and LMB population terms, it has highest percentage of its national population in the LMB. Cambodia follows a close second with almost 10million people and 74% of the country's population living in the LMB. Table 10.5: Total population of the Lower Mekong Basin Population in Percent of Country Total Population LMB Population in LMB Cambodia 13,300,000 9,800,000 74% Laos 5,680,000 4,905,000 86% Thailand 63,960,000 23,130,000 36% Vietnam 80,900,000 16,920,000 21% Total 163,840,000 54,755,000 33% Source: Asian Development Bank, 2003 201 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | SOCIAL SYSTEMS The Mekong River Commission (MRC) in its recent "Integrated Basin Flow Management Progress Report"68 classifies a 15km wide corridor on either side of the Mekong River as the highest impact area for hydropower on the mainstream. Table 10.6 shows corridor populations totaling approximately 23,500,000 persons. At more than half the corridor population (51.2%), Vietnam has both the highest population numbers and greatest population percentage, and Cambodia the highest national percentage (57.2%), living in the 15km Mekong corridor. Table 10.6: Populations in a 15km corridor adjacent to the Mekong River % of national % of corridor Corridor population living population per Country Population in the corridor country Cambodia 7,601,352 57.20% 32.50% Laos 2,004,515 35.30% 8.60% Thailand 1,901,171 2.80% 7.60% Vietnam 11,974,813 14.80% 51.20% All countries 23,481,851 Source: Table 3, Mekong River Commission, "Integrated Basin Flow Management Progress Report (IBFM)", 2007 Indirect impacts may affect a larger number of people, but less drastically and immediately than direct impacts. Adverse indirect impacts are most likely to be experienced in the Mekong corridor, and mainly by those living within good proximity of the Mekong river (i.e. within 5kms.). While total corridor population amounts to more than 23 million people, 78% of these (18,382,086) live within 5kms of the Mekong mainstream69. Of the 4 LMB countries, Vietnam has the highest dependent proportion of its corridor population living in closest proximity to the Mekong (89%), followed by Cambodia (78%), Laos (50%) and Thailand (38%). The proportion of dependency reflects both the very high rate of dependency in different countries on Mekong river irrigated agriculture (Vietnam) and fisheries (Cambodia). Laos has a substantial percentage of its riparian population (50%) within 5kms proximity, while Thailand has the least (38%). Indirect transboundary impacts may also be experienced where watersheds cross national boundaries. If watershed environmental loss occurs in one country due to activities such as illegal logging or land clearance for foreign concessions, this may have erosion consequences, with subsequent sedimentation impacts on reservoirs in another country. In situations such as these, without prior transboundary discussion and agreement, it will be more difficult to assign responsibility for indirect impacts, and therefore to agree budget allocations and remedial measures. Ideally, the situation should not arise in the first place, with transboundary agreements in place beforehand. Apart from immediate proximity to the Mekong river described above, local administration is also affected by hydropower projects. Stakeholders providing feedback to the SEA indicated that relative capability and transparency of local administration has a direct bearing as to the severity or otherwise of social and livelihood impacts. Table 10.7 shows the number of provinces, districts and their populations for each dam. This shows that Pak Chom and Ban Koum will affect the largest number of districts, and the 68 Mekong River Commission, "Integrated Basin Flow Management Progress Report (IBFM)", 2007 69 Mekong River Commission, "Integrated Basin Flow Management Progress Report (IBFM)", 2007. 202 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | SOCIAL SYSTEMS highest district populations will fall in their ambits of activity. These are the districts where indirect impacts will be most experienced, and the Table shows the total population of all districts in the 3 immediate impact zones of head pond, construction site and immediate downstream areas (20kms). Several districts are affected by more than one dam (Annex A), but the overall total counts each district once only. Table 10.7 lists the largest total district population potentially affected by mainstream dams. However, these figures must be used with caution as not all people in a riparian district will be directly or indirectly affected by Mekong mainstream dams, depending on their proximity to the river. Furthermore, additional people may be indirectly affected, particularly in hinterland districts dependent on connected river systems which may experience water flow changes, increased sedimentation, or fish reduction. This would include substantial numbers of people in the Tonle Sap who are annually or seasonally dependent on fisheries for their livelihoods. Cambodia will be most indirectly affected, with an estimated 43% loss in its fisheries, followed by Vietnam with an estimated 23% loss70. In Cambodia, this works out at some 1 million fisheries‐dependent livelihoods at risk. Table 10.7: Number of affected provinces, districts and district populations for Mekong mainstream dams Total Affected No. Affected No. Affected District No. Dam Name Provinces Districts Population 1 Pakbeng 4 8 223,659 2Louang Prabang 2 4 159,204 3 Xayaboury 2 4 202,198 4Pak Lay 3 7 282,544 5 Sanakham 2 4 160,974 6Pak Chom 4 13 588,189 7Ban Koum 3 8 413,140 8Lat Sua 2 4 255,160 9Don Sahong 2 5 250,217 20 Thakho NA NA NA 11 Stung Treng 1 2 52,326 12 Sambor 1 2 145,610 Totals 13 47 2,094,749 Sources: Government of Lao PDR Population Census 2005, Kingdom of Thailand Population Census 2008, and Kingdom of Cambodia, Population Census, District Population Figures 2008 70 Ton Lennaerts, "Economic, Environmental and Social Impact Assessment of Basin‐wide development scenarios", Initial Findings from Assessments, Mekong River Commission, RTWG presentation, February 2010 203 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | SOCIAL SYSTEMS 10.7 POVERTY REDUCTION IMPACTS Positive indirect impacts from allocating hydropower revenues to poverty alleviation cannot currently be quantified in terms of people benefiting, as neither the percentage of revenues towards health, education, road development and environmental protection are generally agreed, neither are the locations yet known where these funds could be spent. As the SEA baseline indicated, the higher the level of dependence on natural resources, the greater the opportunities for impoverishment to communities affected by any change in such resources. This is notable when comparing poverty levels between Thailand and Laos, for example71. Although Thailand has the largest number of people living in the LMB, Laos has the highest percentage of its population living in the LMB. In Champassack province (Laos) compared to Ubon Ratchathani province (Thailand) on the opposite side of the Mekong, we have seen the percentage of poor households in each province – Champassack 19.7% of the population, vis‐a‐vis Ubon Ratchathani 0.3% of the population. Impacts from land loss will have substantial impacts on communities who are highly dependent on the natural resource base for their livelihoods. An estimated total72 of 7,499has of agricultural land (see Annex B) will be acquired for all the proposed projects, of which 829has are irrigated. An estimated 19,855has of forest land will be lost. Replacement agricultural land, particularly in Zone 2 dams areas, is extremely scarce. Without due care and consideration on this point, and if support is not provided to affected households to bring replacement land into cultivation, greater impoverishment could result for affected communities. The concept of vulnerability is not just linked to the ability to resist project‐induced impoverishment, but also to resist social impoverishment. Social impoverishment includes that which disrupt homogeneous and co‐dependent communities by forced displacement from locations where they have developed economic, cultural, spiritual, and social relationships. When compensation is restricted to cash alone, this leaves relocation choice to individual households, who may not be able to replicate their social structures and who are removed from their cultural and spiritual ties, and completely fails to account for loss of common property resources. Community institutions and social networks are weakened, cultural identities and the potential for mutual self‐help are diminished or lost73. In addition to land‐based livelihood resources, community facilities will also be affected. Some 8 schools, 5 temples and a cemetery will be destroyed. Numerous cultural sites will be affected with impacts on livelihoods related to tourism. These include possible impacts on the Pak Ou caves (Louang Prabang), the Khone Phishing falls (Stung Treng and Thakho), and the Ramsar site of Stung Treng. 71 Mekong River Commission, "Integrated Basin Flow Management, Progress Report", Social Assessment Team, Water Utilization Program/Environment Program, June‐August 2007 72 These figures are minimum totals as of the time of this report. Two developers did not complete the estimates for land acquisition. Moreover, estimates of acquired land only relate to those directly affected by relocation, and do not include estimates of land acquisition for associated facilities such as access roads, transmission lines, etc. Total figures of land loss may thus be higher. 73 World Bank, (2001) Operational Policy 4.12, Involuntary Resettlement, paragraph 1 204 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | SOCIAL SYSTEMS Care will be needed by hydropower developers to ensure that community assets and infrastructure are promptly replaced if communities are not to suffer intellectual and cultural impoverishment. Associated is the need to relocate communities as discrete village units in order to avoid additional social impoverishment and marginalization. The key as to whether hydropower development is an effective response to poverty alleviation is not whether the national resource base of the Mekong river and LMB countries' river systems provide opportunities for economic development, but: 1. whether the offset of resources, individual and community assets, and livelihoods, lost in the hydropower development process are comparable to resources gained as a result of hydropower operations; 2. whether livelihood restoration is afforded the same importance for planning mitigation measures as asset replacement; 3. whether affected people experience the "double jeopardy" of forced relocation within a short period, thus making them even more disadvantaged; 4. whether replacement land of equal size and productivity is available or not; 5. whether positive revenue generation is equally matched by effective expenditure management for poverty alleviation; 6. whether those responsible for constructing and managing hydropower projects are as competent in social, livelihood and environmental design and risk mitigation management as they are in engineering design and management; 7. whether local administrative capacities are sufficient to link relevant national poverty alleviation policies to on‐the‐ground hydropower‐related activities; 8. whether the number of affected people are correctly estimated beforehand or not; 9. whether adequate budget allocation is made before and during project implementation. 10.8 HEALTH AND NUTRITION IMPACTS When livelihoods are disrupted or natural‐resource dependent communities are increasingly removed from traditional livelihood sources, then the incidence of stunting, wasting and associated diseases increases as the food chain is disrupted or cut off. Dependence on wild foods, including aquatic species, is extremely important for both food security and nutritional intake, particularly for poorer and vulnerable families, and cannot be easily substituted by meat from livestock due to problems of storage, transport, land availability to raise livestock, and costs of maintaining domestic animals. Indeed, some nutritional specialists74 refute the idea that rice insufficiency is the cause of food insecurity in the LMB, rather that it is due to loss of wildlife habitat and resources (not just fisheries) which is eroding the nutrition base and contributing to greater food insecurity. This factor is confirmed by a recent MRC study75 which notes that proximity to the Mekong mainstream is essential to dependency levels on the river's ecosystem. This was particularly noted in areas such as northern Laos, where the topography shows steep land elevation from the river bank, and upland communities living less than 15kms from the Mekong river showed little or no use of its aquatic 74 Jutta Krahn & Arlyne Johnson, "Upland Food Security and Wildlife Management", Juth Pakai, Issue 9, 2009 75 "Integrated Basin Flow Management, Progress Report", Social Assessment Team, Mekong River Commission Water Utilization Program/Environment Program, June‐August 2007 205 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | SOCIAL SYSTEMS resources. By contrast, the study notes that where the topography makes the Mekong river more accessible, as in the Tonle Sap in Cambodia, people travel considerable distances each year to profit from the seasonal fisheries opportunities. Thus a combination of easy access with proximity are determining factors of the extent of use of the Mekong river's aquatic resources. Inevitably in many riparian provinces, Mekong mainstream communities depend heavily on fisheries and aquatic food sources for both consumption and livelihood, compared with communities at a distance from river sources. While the sources of these fisheries and aquatic foods are varied, the most important is the Mekong river, accounting for an approximate 37% of riparian communities' fisheries and 39% of the Tonle Sap fisheries alone76. Any changes to these resources would have severe consequences for riparian communities' protein intake, food security and overall health status. Risks of adverse health impacts associated with presence of external migrant workers also exist. Five hydropower developers responded to the SEA team's queries about estimated number of workers required. Most projects estimate an average of 3000‐6000 workers per project will be needed. While some opportunities may be available to local communities, more typically a developer brings in outside contract labour for the duration of the project. This can cause easier disease transmission through poor living conditions, as well as higher incidence of sexually‐transmitted diseases between the local population and outside workers. 10.9 RESETTLEMENT RISKS Several key stages of planning and management are required, associated with the phases identified above, but more importantly including a pre‐construction phase, to ensure that social, environmental and livelihood risks are properly recognized, and to enable satisfactory plans to be prepared to ensure that impact risks are reduced and comprehensively addressed according to international standards. These risks may not only result from planning processes, but may range widely from location to location. Risks are lower in locations where little resettlement is required and few natural resources are affected. Typically this occurs either in locations where few people live or work on affected land, where technical design is adjusted specifically to minimize human impacts, and where technical remedial measures, such as embankments, are constructed thereby avoiding forced displacement. Risk assessment stages include: • pre‐construction planning (socio‐economic assessment should be separate from an environmental assessment and employ different skills; this phase also identifies where displacement avoidance or minimization options can be reviewed and applied) • construction phase (site impacts include: land acquired for dam, access roads, transmission lines, contractors camps, spoil areas, etc.) • impoundment phase (upstream impacts include: land and riverbank gardens inundated, groundwater levels elevated, aquatic resources affected, livelihoods de‐constructed, uncontrolled immigration, loss of submerged cultural heritage and community assets; impacts also experienced in areas affected by associated facilities, such as transmission lines) • operational phase (livelihoods reconstruction of displaced people still needed, benefits sharing clarified, downstream impacts include: erosion, aquatic resources affected, loss of riverbank gardens, adverse changes in agro‐production systems) 76 Mekong River Commission, SIMVA, November 2009 206 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | SOCIAL SYSTEMS The consequences of land expropriation practices in all the LMB countries as previously described in the baseline, have subsidiary significance for Mekong mainstream dam development, and may create a state of "double jeopardy". This applies to: land users of land expropriated for concessions holders which may be adjacent to the Mekong mainstream river (e.g. in Champassack province, Lao PDR and Stung Treng province, Cambodia), and could fall into the impact zones. There is no policy guideline to compensate concessions holders who have been awarded land already expropriated from its original land users. Land use details from Cambodia were not provided to the SEA team, as this is considered a sensitive subject. communities who have already been relocated under national strategies (e.g. Hmong in the Pak Beng impact zone) and risk suffering displacement a second time landowners/users along the Mekong mainstream, cultivating land typically among the most agriculturally productive, where land‐for‐land compensation is unlikely to be viable as it has already been allocated to other interests, or is in such short supply that land of equal productivity and value is unlikely to be available To address this under hydropower development requires collective, transboundary and coordinated action which seeks a balance between poverty alleviation, economic development, social and ecological integrity. 10.10 TRANSBOUNDARY RISKS There are transboundary risks associated with different types and principles of compensation and mitigation measures being applied by different developers in a single country, as well as by any one developer creating impacts in more than one country. The extent of risk depends on: 1. whether a developer is willing to change technical design of a dam to minimise impacts; 2. whether national policies and strategies have a good chance of being applied in practice, not just in principle; 3. familiarity levels in provinces and districts of compensation and mitigation policies, legislation and related implementing procedures; 4. ability and/or willingness of national agencies to monitor resettlement and livelihood restoration activities, and ability to insist on changes and/or compliance with agreements; 5. extent of preparation, competence and budget allocation by the developer to treat resettlement issues with the same professional seriousness with which engineering issues are addressed 6. whether a process of adaptive management is accepted and applied to address issues which could not have been anticipated during the planning period. The issue of resettlement is normally assigned to national policy implementation, and therefore assumed to have no transboundary impacts. This assumption is incorrect with respect to proposed Mekong mainstream dams. There are several reasons for this. The first is the broader definition of "resettlement" that is now applied by international financing agencies, as described in the baseline. Secondly, mainstream run‐of‐river dams or barrages have land acquisition and livelihood impacts on both sides of the river, as well as upstream and downstream of construction sites. Where the river forms an international boundary, there will consequently be impacts in both countries, and downstream impacts will be experienced across national boundaries. 207 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | SOCIAL SYSTEMS Impacts can, however, often be difficult to assign as national or transboundary. In the SEA's national scoping workshop (July 2009), it was pointed out that many current transboundary complaints remain unresolved. For example, Cambodia accuses Laos of downstream problems caused by waste disposal and contamination of waterways by plastic bags. Laos counters these with accusations of its own that Cambodian boats illegally cross boundaries and cause the problem. What this demonstrates is not just that there are grievances, but that there is currently no process or framework in place to deal with accusations and counter‐accusations of who is responsible for what. This has implications of transboundary impacts related to hydropower activities. 10.11 RESETTLEMENT Strategic transboundary issues relating to Resettlement impacts include: 1. Variability of LMB country legislation relating to potential social inequity of treatment of Affected Persons (APs). Each LMB country has its own land acquisition and compensation laws and policies. Some are more comprehensive than others. Although impacts may be the same on both sides of the river, actual compensation and mitigation measures may be different, leading to social inequity in treatment of people affected in the same way by the same project but living on opposite banks of the Mekong river, or living upstream or downstream of the construction site. 2. International financing safeguard standards. If any developer seeks financing from an International Financing Institution (IFI) which has either developed its own safeguard policies or subscribes to the Equator Principles, common land acquisition and compensation, mitigation and livelihood restoration standards are required to be applied to the highest, rather than the lowest, levels irrespective of individual country systems. 3. Definition of locations deemed affected. Not every country nor every developer recognises and accepts that mitigation measures, compensation, and livelihood restoration, apply to impacts experienced in all 3 locations outlined above. Most consider the construction site and land lost to impoundment as being the extent of responsibility for compensation, and that this can be addressed through cash payments. Consequently associated impacts, such as downstream impacts, health consequences of elevated groundwater levels adjacent to headponds, and livelihood restoration, may be left out of the resettlement planning equation. 4. Minimal safeguards standards approach. Where a minimal standards approach can be applied, a developer may disregard even national land acquisition and compensation standards, and national agencies themselves may be unwilling or unable to monitor their application, or monitors in one country may be more effective than in another country on the same project. This also could lead to further substantial inequities for affected people, with one country more effectively protecting the rights of its citizens than another. 5. Consistency of developer's approach needed. If all countries support the premise that the developer is responsible for compensation and mitigation measures, a consistent approach throughout the LMB countries is necessary concerning the developer's responsibilities towards a land acquisition, compensation, mitigation measures and livelihood restoration programme, which does not depend solely upon cash compensation, but is approached as a development project in its own right. 6. Political unrest caused by social discontent among affected people in one country could cause construction delays, causing associated construction delays in the transboundary country and resulting in overall higher construction costs for the developer, delays in meeting power purchase agreement deadlines and possible consequent financial penalties. 208 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT | SOCIAL SYSTEMS 7. Disease does not recognise national boundaries. Existing health problems which could be exacerbated by construction and operational activities, and development of new problems, need a coordinated transboundary approach to anticipate and address. 8. Natural phenomena, such as naturally‐occurring arsenic in groundwater, are also not restricted to one country. Again, a coordinated approach is required to address potential risks to human health. 9. Transboundary watershed management may be required in some locations to avoid additional operational resettlement impacts due to erosion, particularly in Zone 2 locations between Thailand and Laos, and in Zone 4 between Laos and Cambodia. 10. Those engaged in the illegal activity of human trafficking routinely circumvent national policies and procedures. Improvement of communications and transport networks require associated improvement of transboundary frameworks to deal with this. 11. Lastly, operational procedures need transboundary agreements on dam safety and downstream flood preparedness. A large dam does not need to fail to have severe consequences, and notification procedures and preparedness are essential, as are downstream early warning procedures in case of sudden water releases, particularly in densely populated areas such as the lower reaches of the LMB. The resettlement component of any project is often the weakest component in a dam developer's armoury. This is unwise at best, as it risks contributing to substantial cost overruns, implementation delays and more adverse impacts on a larger number of people. At worst it can lead to considerable social and political unrest, and is a high risk approach for any LMB country. 209 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE 11 CLIMATE CHANGE 11.1 STRATEGIC ISSUES 1. What changes are foreseen in climate and hydrological variability and extremes? 2. What implications will those changes have for natural and social systems in the basin? 3. What implications will those changes have for development sectors in the basin including hydropower? 11.2 SUMMARY OF PAST & FUTURE TRENDS WITHOUT LMB MAINSTREAM HYDROPOWER Already, climate changes in the Mekong region are influencing ecosystems, livelihoods and development through changes in regular weather – i.e. daily, seasonal and annual patterns – and through irregular extreme events. The main influences (and indicators of change) are temperature, rainfall and runoff, sea level, tidal fluctuations and extreme events such as storms, floods and drought. Over the past 3 to 5 decades, trends of increasing mean annual temperature have been recorded in each LMB country. Most notable is the increase in variability from one year to the next. The trends in rainfall are less consistent with increasing variability and extremes between wet and dry in Laos and Cambodia, a decrease in rainfall in Thailand, and decreases in most localities in the north of Vietnam with increases in most areas of the South during all seasons. During winter in Vietnam overall rainfall fell by 23%. Seasonal changes are important, with most increases in rainfall occurring during the wet season. All countries have experienced decreasing rainfall during the dry season with aggravated drought and water stress situations in many catchments. Future climate to 2030 is projected to include steady increases in mean basin temperature by 0.8°C. Greater increases are expected in northern zones of the basin up to 1.4°C in Yunnan Province. Annual rainfall would increase by 13.5% (0.2m) mainly due to increases during the wet season (May to Oct). Dry season rainfall will increase in northern zones (1 and 2) and decrease in southern zones (3 to 6 – ie from Vientiane to the Delta). The overall disparity between wet and dry seasons will increase especially in zones 3 to 6. Total annual runoff from the basin is projected to increase by 21% mainly during the wet season with the annual discharge at Kratie increasing by 22% with increases in all months but mainly the wet season. This projection takes into account estimates for water use by future populations in the basin and irrigation. Flooding is projected to increase throughout the basin – with downstream zones affected most. For example at Kratie (zone 5) the annual probability of extreme wet flood events will increase from 5% (ie historic conditions) to 76%. It will increase to 96% in the wet season. The duration of flooding will increase in this zone with an earlier onset. The maximum and minimum area and water levels in Tonle Sap would increase annually. The annual average flooding in Delta would also increase by 210 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE 3,800km2. The impacts of this increase in flow and flooding could be expected to be greatest on the mainstream Mekong due to cumulative contribution from tributaries. Despite rainfall increases, zones 3 to 6 (the Mekong below Vientiane) are projected to experience reduced rainfall and runoff during the dry season. Southern Laos, Northeast Thailand, Central and Southeastern Cambodia, including the Tonle Sap catchment and the Delta region are still susceptible to high water stress during the dry season. More dry spells and a greater severity in drought periods are expected. The past trend of increasing variability with greater extremes between wet and dry seasons, especially in southern and eastern areas, it projected to continue. The projected 2030 increases in temperature, rainfall and runoff with more extreme climate events will influence the productivity of economic sectors and livelihoods. Overall agricultural productivity will increase in the basin (around 3.6% by 2030) but food security will decrease, despite the increasing areas under irrigation. Those decreases are due to reduced dry season rainfall and runoff in central and southern zones, increasing populations and reduced production in excess of demand and increasing saline intrusion in the Delta due to storm surge and tidal influences and decreases in dry season rainfall and runoff. Overall fish biodiversity and stability in fisheries sector production is expected to decrease in the basin despite some climate change benefits of increasing flooded area and nutrient loading. The decreases are due to the complex interplay between decreased agricultural productivity and food security increasing demand and pressure on fish populations, increased riparian populations, reduced fish migration and aquatic biodiversity in zone 1 and in Mekong tributaries due to dam and infrastructure construction, and reduced and disturbed habitat due to a combination of climate change and development. The benefits to productivity of increased nutrients due to increased runoff and erosion with climate change may be offset by reduced sediment due to China and tributary dams, especially in the central highlands of Vietnam. Hydropower: Overall the hydropower sector will benefit from climate changes from increased capacity in basin catchments, but there are risks. Increased rainfall, runoff and flow throughout basin would increase potential capacity of hydropower generation in both the tributaries and mainstream for hydropower. Some catchments will experience very high increases in runoff and water volume – possibly beyond the capacity of existing tributary dam schemes – creating risk of failure and need for retrofitting. Increase in extreme wet events and incidence of flood events brings a risk of catastrophic failure (climate change may turn a 1 in 10,000 year flood risk into a more regular event – for example to a 1 in 1,000 flood). Livelihoods: Aquatic and terrestrial natural systems are under increasing stress in the Mekong basin. While there are benefits, overall climate change will increase that stress by increasing the need to make agriculture more productive and extensive and by increasing pressure to exploit aquatic resources. Overall reductions in fish habitat, feeding and nursery areas and increasing water stress in some catchments and the frequency and intensity of drought periods will all have knock‐on effects on livelihood activities. Other developments, such as hydropower dams, intensify natural system stress and the negative effects of climate change. Climate changes such as temperature and rainfall increases and increased incidence of flooding will also increase health risks which would reduce labour productivity and increase levels of poverty. 211 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE 11.3 EXPECTED DIRECT EFFECTS OF THE PROPOSED LMB MAINSTREAM HYDRO PROJECTS While the MRC now includes climate change analysis in its basin planning, the more recent feasibility designs of the LMB mainstream projects prepared by private sector and institutional agency developers have not taken climate change explicitly into account. In part this is because of the lack of project‐level methodologies for doing so. The variation in modeling results and unreliable baseline information increase the uncertainties of climate changes and their effects. Yet, even if the most modest projected changes are considered – rather than ranges between extremes – the relationships between the proposed mainstream projects and climate change is likely to be significant. The effects fall into three categories: (i) the direct effects of the projects on climate change, (ii) the direct effects of climate change on the projects and (iii) the complex inter‐linkages between climate changes, the mainstream dams and other sectors. The effect of the projects on the human drivers of climate change is through the emission of green house gases and clearing of forests which act as carbon sinks. The direct effects of climate change impacts on the projects are through increased runoff and flow and in extreme flood events. 11.4 EFFECTS OF THE LMB MAINSTREAM PROJECTS ON CLIMATE CHANGE ‐ GHG EMISSIONS77 Climate change has mitigation and adaptation dimensions. Mitigation as it relates to human induced climate change in the context of the SEA concerns the net potential impact on GHG emissions in the power sector both nationally and regionally. It is well document by the United Nation’s Clean Development Mechanisms (CDM)78 that two primary considerations in the hydropower and GHG mitigation linkage are (i) the extent to which existing and potential future emissions from thermal power stations are avoided (e.g. GHG emissions from coal, oil and natural gas) when hydropower displaces thermal generation, and (ii) the various potential GHG emissions that arise from creating reservoirs including CO2 and methane (CH4) and other phenomenon such as degassing that often occurs in deep reservoirs when reservoir water is released from deeper layers and pressurized gas is released into the atmosphere , Table 4.2 in Section 4 of this report provided preliminary calculations of the amount of thermal avoided emissions (or gross emission reduction) from LMB hydropower. The calculations are based on the specific type of thermal project that LMB national hydropower, or hydropower imports in the case of Thailand 77 ICEM collaborated with Matti Kummu of the Water & Development Research Group, Aalto University, Finland on the GHG emission estimates. The full results of the emissions work is to be published in Environmental Science & Technology by Matti Kummu, Timo Räsänen, and Olli Varis as: Kummu, M., Räsänen, T. and Varis, O. submitted. Greenhouse gas emission estimations for existing and planned reservoirs in the Mekong Basin 78 The Clean Development Mechanism (CDM) is established under the United Nations Framework for Climate Change Convention (UNFCCC) and defined in Article 12 of the Kyoto Protocol. It allows a country with an emission‐reduction or emission‐limitation commitment under the Kyoto Protocol (Annex B Party) to implement an emission‐reduction project in developing countries. 212 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE and Viet Nam, would displace in each LMB country. 79 The analysis indicates that the MRC BDP 20‐year probable future (PF) scenario would result in gross GHG emission reductions in the LMB power sector of some 42 million tones of CO2 annually in the year 2030. The 20‐year PF scenario with all LMB mainstream dams would result in gross GHG reductions of some 94 million tones of CO2 annually in 2030. The rest of this section focuses in discussion of GHG emissions that LMB reservoirs may produce, recognizing that calculation of emissions from reservoirs is a much more complex undertaking than the calculation avoided thermal power station emissions. It brings into play assumptions about the complex interaction of many bio‐physical systems and sub‐systems. It is important to note at the start that the issue of reservoir GHG emissions is a highly contested topic world‐wide. The nature of the scientific controversy and expert debate is documented by the World Commission on Dams (2000) and in the more recent positions captured on the websites of international organizations such as the International Rivers Network IRN) 80 and the International Hydropower Association (IHA) 81. The International Hydrological Programme (IHP) of UNESCO82 is also working with the IHA to improve the level of scientific understanding on the impact of reservoirs on natural GHG emissions in a whole river basin context, obtaining a better comprehension on current methodologies and helping to overcome knowledge gaps. Very different methodologies for estimating reservoir emissions have thus emerged. Because of uncertainty and ongoing scientific debate, the Inter‐governmental CDM Executive Board provided guidance on thresholds and criteria that should be considered for CDM submissions that involve hydropower projects, namely:83 “ Noting the scientific uncertainties concerning green‐house gas emissions from reservoirs and that these uncertainties will not be resolved in the short term, a simple and transparent criteria, based on thresholds in terms of power density (W/m2), are to be used to determine the eligibility of hydroelectric power plants for CDM project activities. The CDM thresholds are as follows: i. Hydroelectric power plants with power densities (installed power generation capacity divided by the flooded surface area) less than or equal to 4 W/m2cannot use current methodologies; ii. Hydroelectric power plants with power densities greater than 4 W/m2but less than or equal to 10 W/m2can use the currently approved methodologies, with an emission factor of 90 gCO2eq/kWh for project reservoir emissions; iii. Hydroelectric power plants with power densities greater than 10 W/m2can use current approved methodologies and the project emissions from the reservoir may be neglected.” 79 The calculation is relatively straight forward. The CDM also provides methodologies to make this calculation when it considers applications. 80 http://www.internationalrivers.org/en/node/383 81 http://www.hydropower.org/climate_initiatives.html 82 UNESCO http://typo38.unesco.org/index.php?id=240 83 CDM – Executive Board(EB) 23 report Annex 5 page 1: Thresholds and criteria for the eligibility of hydroelectric power plants with reservoirs as CDM project activities 213 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE Accepting there are different methodologies, the preliminary analysis presented here aims more to illustrate the sort of framework needed to strategically consider this issue. At the same time it provide insights on what may be required for further comparison, refinement and selection of methodologies appropriate for the Mekong setting and gives an idea of the relative possible emission effects of the different types of power generation projects. Common to all methodologies, the reservoir area is an important factor influencing total GHG emissions from hydropower projects. About 11% of the region’s existing and planned reservoir area to 2030 (i.e. BDP 20 Year Scenario with mainstream dams) is located in the UMB (i.e. China) all along the mainstream Mekong. Proposed LMB mainstream projects cover 27% of the total while LMB tributary projects will make up 62% of total reservoir area. The difference in reservoir area is reflected in the projected GHG emissions to 2030 (Table 11.1). The ecological zones in which reservoirs are located are also influential – especially slope, temperature and land cover characteristics. The general pattern that emerges is mainstream reservoirs located in the more temperate mountainous areas of zone 1 in Yunnan Province (UMB) would release less GHGs than the mainstream dams proposed for Laos – i.e. in tropical forest zones 2 and 3, which in turn release less than the proposed mainstream projects in Cambodia in the tropical lowland and flood plain areas of zone 4 (Figures 1). This is both in terms of total emissions and average emissions per unit of electricity production. 11.4.1 TOTAL GHG RESEVOIR EMISSIONS This section considers the potential total emissions from the proposed mainstream LMB dams. Again it is important to note there is considerable controversy over the methodology and in particular to highlight that in the methodology used here the carbon sink /source lost due to by the change in terrestrial system inundated is factor in as an “emission”. Later parts of this section compare total reservoir emissions (‐ve) to total avoided thermal emissions (+ve). The two proposed mainstream projects in zone 4 – Sambor and Stung Streng – with their relative large lowland reservoirs, using this preliminary methodology, would contribute 47% of GHG emissions from the existing and proposed mainstream projects from Yunnan Province to the sea (Figure 1). Together they would account close to 80% of average total emissions from the eleven proposed LMB mainstream dams with Sambor releasing more than any other LMB reservoir (Figure 11.2). 214 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE Figure 11.1: Total emissions from existing and proposed mainstream Mekong hydropower projects – 2030 TOTAL EMISSIONS [t/yr ‐ CO2eq (100‐yr)] Jinghong 3% Dachaoshan 1% Nuozhadu Xiaowan 16% 3% Manwan Sambor 0% 35% Latsua 1% Ban Koum Gonguoqiao7% 0% Pakchom 3% Sanakham Stung Streng 3% 12% Paklay Pakbeng 3% 5% Luangprabang Xayabuly Don Sahong 4% 2% 0% Figure 11.2: Average total GHG emissions from proposed LMB mainstream hydropower reservoirs by hydro‐ecological zone ‐ 2030 AVERAGE TOTAL EMISSIONS [t/yr ‐ CO2eq (100‐yr)] PakbengZone 2 LatsuaZone 3 SamborZone 4 Sambor 1,256,267 Stung Streng 435,644 Don Sahong 5,522 Latsua 27,372 Ban Koum 250,443 M'stream AVERAGE TOTAL Pakchom 122,001 ZONE projects EMISSIONS Sanakham 113,787 No. [t/yr ‐ CO2eq (100‐yr)] Paklay 94,572 2 6 125,31 2 Xayabuly 86,859 3394,446 Luangprabang 143,669 4 2 845,95 6 Pakbeng 190,984 M'stream Average 11 269,97 5 When all existing and proposed mainstream and tributary projects in the Mekong Basin are considered, Sambor and Stung Streng stand out as potentially being two of the seven top GHG emitters in relative terms, including the consideration of the loss of the carbon sink (Figure 3). 215 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE Figure 11.3: GHG emissions from existing and planned hydropower project in the Mekong Basin (2030) 1,300,000 1,250,000 Mekong Basin hydropower: Emissions total 1,200,000 1,150,000 1,100,000 1,050,000 1,000,000 950,000 900,000 850,000 800,000 750,000 yr)/GWh] ‐ 700,000 (100 650,000 600,000 550,000 CO2eq ‐ 500,000 [t/yr 450,000 400,000 350,000 300,000 250,000 200,000 150,000 100,000 50,000 0 Koum Paklay Latsua Streng Sahong Sambor Pakbeng Xayabuly Pakchom Ban Sanakham Don Stung Luangprabang ranked distribution of total emissions for tributary & UMB hydropower LMB mainstream hydropower project Given there are 90 existing and proposed LMB tributary reservoirs compared to 11 LMB mainstream projects, it is understandable that total tributary to mainstream total potential GHG emissions are 3:1 (Figure 11.4). On project‐by‐project and total emission basis, the average tributary emissions are potentially about 64% the level of mainstream projects. Figures 11.4 and 5: Total and average GHG emissions from existing and planned Mekong Basin hydropower projects TOTAL EMISSIONS [t/yr ‐ CO2eq (100‐yr)] AVERAGE EMISSIONS [t/yr ‐ CO2eq (100‐yr)] MAINSTREAM TOTALS YUNNAN TOTALS TRIBS TOTALS MAINSTREAM TOTALS YUNNAN TOTALS TRIBS TOTALS TRIBS TOTALS 7,829,578 TRIBS TOTALS 173,991 YUNNAN TOTALS 828,073 YUNNAN TOTALS 138,012 MAINSTREAM TOTALS 2,699,748 MAINSTREAM TOTALS 269,975 11.4.2 EMISSIONS PER POWER UNIT The difference between LMB tributary and mainstream projects may also be compared on the basis of potential GHG emissions per unit of power generated (GWH). This methodology suggests that LMB 216 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE mainstream projects may emit close to 4 times more GHGs per GWH than the UMB mainstream projects. Existing and planned LMB tributary dams, on the other hand, may emit ten times more GHGs per GWH than the LMB mainstream projects (Table 11.1 and 11.Figure 6). Most of the tributary reservoirs involve the clearing of dry or wet tropical forest and a reduction of carbon sink capacity in the basin (Figure 5). Relatively little forest is lost in the LMB and UMB mainstream reservoirs. That marked difference in GHG emissions/GWh between LMB tributary and LMB mainstream projects is explained by the much higher flow and generation capacity on the mainstream. On average the mainstream projects would generate 48 power units/km2 compared to 14 power units/km2 for tributary projects. Table 11.1: Total reservoir area, total annual energy, average GHG emissions and average GHG emissions per unit of power for the three main reservoir groups. Group Area Annual energy Avg. Avg. emissions per unit 2 km GWh emissions of power 3 10 t/yr‐CO2eq(100‐yr) t‐CO2eq(100‐yr)/GWh UMB 650 69,700 829 9 mainstream LMB 1540 66,500 2,725 33 mainstream Tributary 3540 40,400 7,855 343 TOTAL 5730 176,700 11,409 385 217 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE Figure 11.6: Emissions per unit of power for existing and planned hydropower project to 2030 in the Meking Basin Mekong Basin hydropower: Emissions per PU 2,200 2,000 1,800 1,600 1,400 yr)/GWh] ‐ 1,200 average PU emissions from a (100 coal plant are 921 t/yr ‐ CO2eq 1,000 (100‐yr)/GWh. CO2eq ‐ 800 [t/yr 600 400 200 0 ranked distribution of PU emissions for tributary & UMB hydropower Koum Streng Paklay Latsua Sahong Sambor Pakbeng Xayabuly Pakchom Ban Sanakham LMB mainstream hydropower project Don Stung Luangprabang 218 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE Figure 11.7: Total reservoir area per land cover affected in the Mekong Basin ‐ 2030 Of the LMB mainstream projects, Sambor and Stung Streng in hydro‐ecological zone 4 emit on average four to six times more GHGs per power unit than the nine projects in Lao PDR (Figure 6). 11.4.3 EMISSIONS BY ECOLOGICAL ZONE The SEA adopted a hydro‐ecological zonation of the mainstream Mekong and project that through the basin according to tributary sub‐catchments feeding into each mainstream zone. Total emissions for mainstream projects were estimated for each hydro‐ecological zone and by all measures zone 4 in Cambodia becomes the highest GHG emitter (Figure 11.8). 219 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE Figure11. 8: Average total emissions for each unit of power by hydro‐ecological zone AVERAGE TOTAL EMISSIONS per PU [t/yr ‐ CO2eq (100‐yr)/GWh] PakbengZone 2 LatsuaZone 3 SamborZone 4 Sambor 84 Stung Streng 89 Don Sahong 2 Latsua 8 Ban Koum 30 M'stream AVERAGE EMISSIONS per Pakchom 23 ZONE projects PU Sanakham 23 No. [t/yr ‐ CO2eq (100‐yr)/GWh] Paklay 17 26 23 Xayabuly 14 33 13 Luangprabang 26 42 87 Pakbeng 36 M'stream Average 11 34 To compare that performance with tributary projects and according to FAO land cover cateories, all existing and proposed projects in the Basin were overlaid on the land cover classification: • Temperate mountain system (TeM) • Subtropical mountain system (SM) • Tropical mountain system (TM) • Tropical dry forest (TAwb) • Tropical moist deciduous forest (TAwa) • Tropical rainforest (TAr) Figure 9 shows that all the LMB mainstream projects fall within three FAO land cover categories – Tropical dry and moist deciduous forest and rainforest. Annual average emissions per power unit are highest in the tropical dry forest area. The same applies to emissions from tributary projects. 11.4.4 EMISSIONS COMPARED WITH OTHER POWER SOURCES Mainstream reservoir emissions per unit of energy generated are low compared with other dominant sources of grid power supply in the LMB including natural gas, coal and diesel (Figure 10). The average PU emissions from a coal plant is 921 t/yr ‐ CO2eq (100‐yr)/GWh (the rate depends on the type of coal plant as discussed in the alternatives section of the energy and power baseline paper. Sambor and stung Treng have emissions of 85‐90 t/yr ‐ CO2eq (100‐yr)/GWh using this methodology which means that they are the highest for the LMB mainstream projects. Some of the LMB mainstream projects emit less than solar. All emit less per power unit than more conventional generation sources. Nevertheless, using this methodology to calculate reservoir emissions it is suggested that a few LMB tributary dams (up to 3 three) may potentially have larger GHG emissions per GWH than coal, diesel and natural gas (Figure 11.6): 220 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE Figure 11.9: Annual emissions per power unit for each reservoir and ecological zone Perhaps one of the most important questions on this topic is ‐ what is the net impact of hydropower on GHG emissions in the power sector nationally and regionally after taking account of all these factors. This requires subtracting the total reservoir emissions from the total thermal avoided emissions to arrive at an assessment of whether there is an opportunity or risk as regards to climate change mitigation (i.e. a net reduction in human induced GHG emissions and over what timeframe). The analysis presented previously in Section 4 (Table 4.2) suggested that for the hydropower development cases considered in the SEA, the total thermal avoided emissions were from 52 to 94 million tones of CO2 /year by 2030. This is shown in an extraction from Table 4.2 below. 221 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE Table 11.2 GHG emissions offset estimates for with and without mainstream dams GHG EMISSION OFFSET4 (Million Ton CO2/Year) Ton/MWh by Country5 0.86 0.86 0.65 0.97 SCENARIO CAM LAO THAI VIE TOTAL 2030‐20Year with MD 3 18 39 34 94 2030‐20Y‐w/o MD 1 8 17 16 42 2030‐20Y‐ zone 2 only 1 11 33 21 65 2030‐20Y‐ zone 3 only 14 20 1 16 52 2030‐20Y‐ zone 4 only 8 21 3 29 61 Note: Based on avoided thermal generation in the country where power is consumed. The analysis with the methodology in this report suggests the estimated total annual emissions of (reservoirs) amounted to 10.7‐13.0×106 t/yr‐CO2e.q. (100‐yr) for the 20‐year probable future scenario with all proposed LMB mainstream dams. Based on this appears that: 94 million tones Co2/yr avoided thermal emissions (for the 20‐yr 2030 with LMB mainstream), of which 54 million tones is attributed to mainstream dams 13 million tones Co2/yr reservoir emissions and lost carbon sink etc ) of which about 2.7 million tones is attributed to mainstream dams These methodologies suggest there is a net of about 80 million tones CO2 /yr GHG emission reduction in the regional power sector overall by 2030. The portion of his reduction attributed to mainstream dams would be in the order of 50 million tones CO2 per year. This illustrates the scale and dimension of the opportunity for a regional contribution to emission reduction in the power sector, the valuation of which depends on the value per tonne Co2. In summary, because of their large capacity, location and reservoir size, the mainstream projects in Cambodia have high total GHG emissions relative to other hydropower projects in the basin. Overall, the mainstream dams are more attractive than most alternative power sources, other than wind and nuclear, for their relatively small impact on climate change. 222 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE Figure 11.10: Comparison of average emissions per power unit between power sources[t/yr‐CO2eq (100‐yr)/GWh] UMB mainstream 9 Wind 11 Nuclear 22 Tree plantation 32 LMB mainstream 35 Solar 59 LMB Tributaries 343 Natural gas 449 Heavy fuel oil 762 Col 921 Lignite 1,217 0 200 400 600 800 1,000 1,200 1,400 11.5 DIRECT CLIMATE CHANGE EFFECTS ON THE MAINSTREAM PROJECTS 11.5.1 INCREASED RUNOFF, FLOW AND FLOODING The most important climate change effects on the mainstream projects would be (i) the increase in runoff during the wet season bringing with it increases in sediment load, (ii) an increase in annual average flow in the range of 9% (MRC) to 22% (CSIRO) taking into account UMB and LMB mainstream and tributary dams and (iii) an increase in the incidence, depth and duration of extreme flood waters. The MRC modeled increases in flow are for monitoring stations on the Mekong mainstream so the LMB mainstream reservoirs would definitely be affected. MRC modeled 40 years to 2050 and averaged climate and hydrological parameters over that period. With the BDP 20 YR scenario including the LMB mainstream projects and additional tributary reservoirs, MRC confirmed the broad trends of the CSIRO projections of increasing wet and dry season mainstream flow – close to 9% annual average, less than the CSIRO figure. MRC found that flooding incidence would increase with a 12‐82% change in depth in the floodplain for A2 and a 22% increase in flood duration. There would be an increase in areas in the Delta affected by saline intrusion in the range 249 to 1,882 km2 or a 1.4% (B2) to 10.5% (A2) increase. Unlike the UMB mainstream reservoirs which can store and release large volumes of water, the LMB mainstream projects would have no capacity to moderate the increases in flow and flooding due to climate change. Under the LMB 20 year scenarios, there are 70 tributary dams (30 additional to the Definite Future Scenario) with a live storage of 20,185 MCM or 4.2% of Mekong water and 6 Chinese dams – with a total active storage making up 13.5%. The impact of climate change on the frequency of flood events of different magnitude is not well understood, but all studies to date project increases in frequency and magnitude. Depending how the cascades of UMB and LMB tributary dams are managed, the expected increases in flow due to climate change could be moderated to some extent or increased at any point during the wet season. LMB mainstream dams could be subject to seasonal and extreme event peaks in flow well beyond their normal operating design standards. There has been no modeling of the sediment load implications of climate change for the LMB mainstream dams. With a projected 21% annual increase in runoff from basin catchments, soil erosion and erosion of river banks and channels is likely to increase affecting sediment load and water quality in mainstream 223 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE reservoirs. Increased runoff and expected use of pesticides in the basin could also lead to increased levels and accumulation of chemicals in mainstream reservoirs. 11.5.2 RISK OF EXTREME EVENTS Annex 12.2 provides the details of the analysis of likelihood of extreme events with climate change and how that relates to the mainstream dams. Comparing the historic and future climates the following conclusions can be drawn: • The historic 100 yr event is smaller than the 1 in 10yr event with the projected climate change at each station analysed. This means that an event which occurred every 100years is likely to occur more than once every 10 years. • The historic 1,000yr event is comparable in size to the 1 in 100yr event at each station with climate change. This means that the 1 in 1,000yr event will become ~ 1 in 100year event. • The historic 1 in 10,000yr event is comparable to the 1 in 1,000year event with project climate at each station. This is more pronounced for downstream stations Table 11.3: comparison of changes to the magnitude of extreme events for the same return period EXTREME VALUE DISTRIBUTION EXTREME VALUE DISTRIBUTION Project 2030 Return period flow (EV Historic Return period flow (EV dist) dist) with CC Station 10yr 100yr 1,000yr 10,000 10yr 100yr 1,000yr 10,000 Chiang Saen 12,252 14,551 16,808 19,061 13,209 15,769 18,282 20,790 Luang Prabang 17,137 19,912 22,637 25,357 18,783 22,362 25,876 29,384 Vientiane 18,670 21,285 23,852 26,414 19,692 22,745 25,742 28,734 Pakse 40,842 45,344 49,765 54,177 43,459 49,149 54,734 60,311 Kratie 56,254 62,934 69,493 76,040 59,000 66,886 74,629 82,358 Assuming a mainstream project design life of 100years: • Project structures designed for a 1 in 100 year event will see the probability of this event occurring over the design life increase from 63% to ~100% • Project structures designed for a 1 in 1,000 year event will see the probability of this event occurring over the design life increase from 10% to 63% • Project structures designed for a 1 in 10,000yr event will see the probability of this event occurring over the design life increase from 1% to 10% Table 11.4: Probability of occurrence with return periods (T) for an assumed project life of 100yrs T 1 5 10 50 100 500 1,000 2,000 5,000 10,000 50,000 Risk 100.00% 100.00% 100.00% 86.74% 63.40% 18.14% 9.52% 4.88% 1.98% 1.00% 0.20% 224 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE 11.6 INDIRECT LINKS BETWEEN CLIMATE CHANGE, MAINSTREAM PROJECTS AND OTHER THEMES There is an array of important relationships when climate change, the LMB mainstream dams and other major trends in the region are overlaid. 11.6.1 REDUCED FOOD SECURITY There are various trends which have a synergistic effect in reducing food security in the LMB catchments linked to the mainstream projects. The population of the LMB is expected to double by 2030. Food demand would double from ~17 million tonnes for 2000 to ~ 33 million tonnes for the 2030 projected population (CSIRO 2009). With climate change overall agricultural productivity in the LMB is expected to increase by 3.6% due mainly to increased rainfall. Yet, some catchments linked to the LMB mainstream projects will experience reduced rainfall during the dry season, and reduced productivity. Overall, CSIRO conclude that excess production above food demand will be reduced by 56% to ~11 million tones. Even for those catchments with increased productivity, population increases will maintain or create food scarcity situations.84 Another factor working to reduce agricultural productivity will be the effect of the China and LMB mainstream dams on sediment load in flood waters. The China dams are projected to take out some 50% of the total sediment reaching the sea. The LMB project will take out another 10% of that load. Reduced sediment and decreasing overbank and floodplain flooding due to the China dam operations would have immediate impacts on agricultural productivity in affected areas. The extent to which increased sediment entering the mainstream from tributaries in 2030 will compensate for this loss has still to be modeled. In those situations riparian urban and rural communities would look increasingly to the river to offset shortfalls in agricultural produce. This SEA has concluded that, during both construction and operation, the mainstream dams will reduce fish populations, diversity and overall fisheries sector productivity. Therefore the mainstream dams will further aggravate growing food scarcity in the LMB. Agricultural productivity will benefit from increased access to irrigation water from mainstream and tributary reservoirs. Yet, CSIRO found that the irrigation requirement for crops grown in the dry season would be greater for all catchments under the likely future climate – a demand which would need to be met through the increased runoff and reservoir water access. Irrigation systems would need to be designed to meet the increased crop water demand. 11.6.2 REDUCED WATER QUALITY The LMB mainstream reservoirs are relatively shallow when compared to the UMB projects (ie 10‐60m compared to 120‐300m). Even so, 30‐90% of their total reservoir volume is dead storage which during the dry season will affect the rate of flow in the river and turnover of the water body. That will be so especially for the large dams in Cambodia where the river is losing its velocity and dead storage is greater. With climate change the total sediment and organic load entering the mainstream from tributaries would increase. That additional load would be moderated as more tributary dams are built, but ‐ when 84 Food scarcity here means a deficit between availability and demand for agricultural production within a catchment (CSIRO 2009) 225 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE combined with increasing populations and land use changes and disturbance – overall sediment and organic loads reaching the mainstream are likely to increase. Falling agricultural productivity is likely to lead to increased application of agricultural chemicals from relatively low levels now. Also industries are expected to develop along the mainstream and tributaries within a 50 km radius. Those industries and the expanding number and size of urban settlements are likely to increase the pollution loading in the mainstream. The combination of increased sediment and organic loading with increased chemical and organic wastes in certain reaches of the mainstream within reservoirs will act to concentrate and accumulate pollutants bound to organic material, in sediments and in solution. Already, this is becoming a significant problem in the Mekong Delta adjacent to and downstream of industrial and urban areas. Anything structure which impedes flushing and turnover of water volume and sediment will aggravate this growing problem. The mainstream dams would act to concentrate and accumulate pollutants during the dry season. During the wet, thorough flushing is likely although not certain in some reservoirs. For the northern cascade in Zone 2, for example, the full supply level is much higher than the highest recorded water levels near the dam wall (almost twice as high at the dam wall for Luang Prabang). Depending on the location of deep pools, the depth of the water column could be 30m (dam wall) + 50‐90m (deep pool) in which case there may also be mixing and flushing constraints during the wet. 11.6.3 LOSS OF BIODIVERSITY In aggregate, it is likely that climate changes will lead to losses in aquatic and terrestrial biodiversity. Overall reductions in aquatic habitats and shifts in terrestrial ecosystem conditions will combine with human induced changes and disturbances to reduce the basin’s capacity to adapt to change. The “hardening” of land surfaces and of river banks and channels in particular will constrain natural system adaptation to climate change. The mainstream developments would be a significant contributing force in that progressive hardening process. They would act to simplify the aquatic and surrounding terrestrial systems, reducing their diversity, resilience and stability in the face of shocks and stresses. 11.6.4 CONSTRAINTS TO POVERTY REDUCTION Reduced food security, water quality and the diversity and stability of natural systems would make conditions for poor riparian communities more difficult. Losses in aquatic and agricultural productivity would increase food prices and access. Losses in fisheries productivity would limit livelihood and subsistence opportunities. Natural system instability, including landslides, bank collapse, soil erosion and degradation of biodiversity would all affect the poor first and most significantly. The mainstream dams could bring benefits to local poor communities but, when combined with climate change and other trends, a number of influences of the projects would work against poverty reduction. 11.6.5 INCREASED POTENTIAL POWER CAPACITY ACROSS THE BASIS The indirect relationships between climate change and mainstream projects also needs to be overlaid national and LMB power demand. The increased runoff in all LMB catchments with climate change would increase hydropower potential in tributaries – and in the mainstream through increased river flow. The mainstream hydropower projects are being considered as part of LMB country effort to meet growing power demand. While the effects of increased runoff on power capacity of tributaries have not been 226 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE modeled in detail, estimates would suggest that it has the potential to offset the 16% of regional power production estimated for the mainstream projects. Many other factors would come into play in realizing that potential, most notably economic and technical feasibility. 11.7 SENSITIVITY ANALYSIS OF DAM GROUPINGS In undertaking this sensitivity analysis, influential factors are the number of tributaries by hydro‐ ecological zone and their flow contribution to the mainstream in addition to the area and geology of their catchments (Figures 11 and 12). Related factors include climate change effects on agricultural productivity in various tributary catchments, effects of the different project groupings on local fish migration and fisheries productivity, and the likely concentrations of urban and industrial development and populations within reservoir catchments. 11.7.1 CASCADE OF 6 DAMS UPSTREAM OF VIENTIANE (ZONE 2) Increased flow: Total tributary contribution to water flow in this zone is 14% (Figure 12). It will be the zone least affected by projected increases in runoff due to climate change. That contribution is expected to be modulated by a relatively large number of planned tributary dams. Food security: 77% of the mainstream within Zone 2 will be changed by the six reservoirs, with an 82% loss in seasonally exposed in‐channel wetlands and a significant loss in aquatic systems productivity and diversity. All catchments in this zone are expected to suffer losses in agricultural productivity and food deficits. Water quality: The number of dams will have localized effects on flow especially during the dry season which in those reaches of the river would aggravate the concentration and bio‐accumulation of anticipated increases in agricultural, industrial and urban chemical pollutants. 11.7.2 MIDDLE MEKONG DAMS (ZONE 3) Increased flow: Zone 3, with the largest area and a total tributary inflow of 38% will be most affected by projected increases in runoff and sediment due to climate change. Proposed mainstream projects in this zone will be exposed to significant increases in annual volumes of water and in frequency and magnitude of wet season extremes in flood events. Food security: This zone has some of the catchments most seriously affected by reductions in dry season rainfall and agricultural food deficits. In Zone 3, about 22% of the mainstream length will be changed by the reservoir, with about 42% of the seasonally exposed in‐channel wetland areas being lost – leading to overall reductions in aquatic systems productivity. Water quality: The large areas of agricultural land in this zone, the most numerous settlements and increasing pockets of industrial development create potential for relatively high pollution levels in runoff entering mainstream reservoirs. 227 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE 11.7.3 CAMBODIAN DAMS (ZONE 4) Increased flow: 27% of flow is contributed to this zone of the river from three major tributaries in relatively steep terrains. The velocity of runoff in extreme rainfall events will be modulated by intensive development of tributary dams. This zone includes catchments in the Vietnam Central Highlands that contribute around 15% of total sediment to the river. That relatively high sediment load and the projected increase due to climate change will be reduced by the tributary cascades. Food security: In Zone 4, about 43% of the mainstream length will be affected by the reservoirs, with a loss of about 58% of the in‐channel wetland areas with a very significant impact on biodiversity and fisheries productivity. This zone would experience severe food deficits. Water quality: Locally sourced pollution would not be as serious in this zone but the contributions from upstream might become a problem especially for Stung Streng reservoir. Figure 11.11: Mean annual flow contributions to the Mekong River 11.8 SUMMARY OF IMPACTS The relationships between the proposed mainstream projects and climate change is likely to be significant. There would be direct and indirect effects. The direct effects are two way: (i) the contribution of the projects to climate change through green house gas emissions and (ii) the direct effects of climate change on the projects through increased runoff and flow and in extreme flood events. The mainstream projects in Cambodia have high total GHG emissions relative to other hydropower projects in the basin because of their large capacity, location and reservoir size. Yet, overall, the 228 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE mainstream dams are more attractive than most alternative power sources, other than wind and nuclear, for their relatively small impact on climate change. The most important climate change effects on the mainstream projects would be (i) the increase in runoff during the wet season bringing with it increases in sediment load, (ii) an increase in flow in the range of 9% to 22% taking into account UMB and LMB mainstream and tributary dams and (iii) an increase in the incidence, depth and duration of extreme flood waters. LMB mainstream dams could be subject to seasonal and extreme event peaks in flow well beyond their normal operating design standards. Assuming a mainstream project design life of 100years: • Project structures designed for a 1 in 100 year event will see the probability of this event occurring over the design life increase from 63% to ~100% • Project structures designed for a 1 in 1,000 year event will see the probability of this event occurring over the design life increase from 10% to 63% • Project structures designed for a 1 in 10,000yr event will see the probability of this event occurring over the design life increase from 1% to 10% The complex inter‐linkages between climate changes, the mainstream dams and other trends in the Basin would results in some of the most significant synergistic effects. Reduced food security due to climate change would be aggravated by the mainstream dams, as would water quality. The contribution of the projects to hardening of natural systems would increase biodiversity losses and natural system instability. Those factors would affect poor communities most. Increased annual runoff and flow throughout all catchments of the basin would increase its potential hydropower capacity, especially along tributaries. That additional capacity and its technical and economic feasibility requires further assessment as a potential factor influencing the need for or phasing of mainstream projects in meeting power demand. 229 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE 12 ANNEX 12.1 RESERVOIR INUNDATION MAPS 230 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE 231 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE 232 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE 233 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE 234 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE 235 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE 236 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE 237 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE 238 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE 239 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE 240 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE 12.2 CALCULATING THE LIKELIHOOD OF EXTREME EVENTS WITH CLIMATE CHANGE 12.2.1 BACKGROUND TO PROJECTS AND AVAILABLE INFORMATION The LMB mainstream projects have spillway dimensions designed according to the following table. These projects have been designed to withstand a level of risk characterised by the return period for certain design extreme events. MRC is producing design guidelines for hydropower development in the LMB which suggests the use of the PMP (Probable Maximum Flood), but this has not yet influenced the project planning. Table 1: Characteristics of the LMB mainstream project spillway and sediment flushing design (Source SEA Inception Report Vol 2) Spillway Sediment flushing gates no. total equivalent no. total of Dimensions Area Design return of Area Design Reservoir Name gates (m) (m2) Q(m3/s) period gates Dimensions (m2) Q(m3/s) Pak Beng 15 15x23 5,175 27,300 ‐ 3 3x5 45 ‐ Luang Prabang 10 18x22 3,960 44,838 10,000 ‐ ‐ ‐ ‐ Xayaburi 12 18x22 4,752 47,500 10,000 2 3x3 18 140 Pak Lay 12 294x67 19,698 32,526 1,000 ‐ ‐ ‐ ‐ Sanakham ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ Pak Chom 14 20x25 7,000 33,526 100 ‐ ‐ ‐ ‐ Ban Koum 20 20x25.5 10,200 60,972 100 ‐ ‐ ‐ ‐ Latsua 24 20x25 12,000 89,590 10,000 ‐ ‐ ‐ ‐ Don Sahong no spillway ‐ ‐ ‐ ‐ Thakho no spillway ‐ ‐ ‐ ‐ Stung Treng ‐ ‐ ‐ 73,500 ‐ ‐ ‐ ‐ ‐ Sambor* ‐ ‐ ‐ 149,300 ‐ 37 15x20 11,100 5,883 * Sambor project also quotes a "peak inflow" flow of 161,000m3/s. This is likely to be the probable maximum flood event The MRC has provided the annual maxima series for five gauging stations along the Mekong mainstream: Chiang Saen, Luan Prabang, Vientiane, Pakse and Kratie. The length of the time series is typically 50‐ 100years and the relationship between the stations and the mainstream projects is presented in the table below: Figure 1 presents the ranked annual maxima series for Kratie as an example (graphs for the other stations are presented in the Annex). The series represents the largest flow event to occur at Kratie during each calendar year at a daily‐time step. The average annual maximum value over the 86 year period is 51,264m3/s and the series hasd a standard deviation of 8,395m3/s. Table 2: Summary of the available hydrological data and the relation to the mainstream projects 241 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE Station Zone Mainstream Start of End of Length Origin of data dam record record of record Chiang Saen 1/2 Pak Beng 1960 2009 50 DB of origin ThaiLand1\Db\Hymos Luang Prabang 2 Luang Prabang 1939 2009 71 DB of origin Laos1\Db\Hymos.mdb Xayaburi Pak Lay Vientiane 2/3 Xanakham 1913 2009 97 DB of origin ThaiLand1\Db\Hymos Pak Chom Pakse 3/4 Ban Koum 1923 2009 87 DB of origin ThaiLand1\Db\Hymos Lat Sua Don Sahong* Kratie 4 Stung Treng 1924 2009 86 Sambor * Don Sahong is on one channel of the Mekong River Figure 1: Ranked annual maxima series for Kratie 1924 ‐ 2009 Adamson (2009) has already estimated the flood risk in Zone 2 at Chiang Saen, Luang Prabang and Vientiane (Table 2). Adamson used the General Extreme Value Distribution method. He compared the type I, type II and type III distributions and found that type III suggested that annual maximum floods of the Mekong are bounded by some upper asymptote and provided a lower estimate for larger events than the Type I distribution (See figure 2), therefore he selected the Type I distribution so that a conservative estimate is used. Table 3: Estimate flood risk on the Mekong River in Zone 2 (Source: Adamson, 2009) GENERAL EXTREME VALUE DISTRIBUTION Return period flow (GV dist) Station 10yr 100yr 1,000yr 10,000 Chiang Saen 14,000 19,000 24,000 ‐ Luang Prabang 19,800 26,500 32,800 ‐ Vientiane 21,100 27,200 33,000 ‐ 242 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE Comparing Table 1 and table 3 it can be seen that the 1 in 1,000yr event at Pak Lay is comparable to the same event at Vientiane gauging station. Figure 2: Plot of the Extreme Value Distributions for Luang Prabang: the exceedance probability is related to the recurrence interval as its inverse (Source: Adamson, 2009) 12.2.2 SUMMARY OF CLIMATE CHANGE IMPLICATIONS FOR EXTREME EVENTS Predictions of climate change for the LMB estimate that there will be: i. An average 22% increase in annual run‐off by 2030 (~107,000mcm for the basin). This will be concentrated in the wet season (Eastham et al, 2008). ii. Increased flooding will affect the entire basin but will be most exaggerated in downstream sections where the low elevation flood plain dominates the hydrology (Eastham et al, 2008). iii. For Kratie, Eastham et al (2008) estimated there will be a significant decrease in normal, significant and extreme dry events, with an increase in significant and extreme wet events. The extreme event is the 1 in 20yr event and the significant event is the 1 in 10yr event. These definitions are based on the MRC, and are designed for flooding in relation to agricultural use and irrigation. They do not define extreme events for large infrastructure like the proposed hydropower development iv. The CSIRO study identifies an extreme event as one with an annual probability of 5% under historic conditions (i.e. a return interval of 1 in 20yrs). With moderate estimates of climate change this same event will have an annual probability of 76% (i.e. a return interval of 1 in 1.3 243 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE years).85 For wet climate change projections the 1 in 20yr event will become the annual flood event. v. The increase in extreme flood is driven by a greater peak and increased duration (Eastham et al, 2008). vi. For Kratie, the historic wet season mean annual peak monthly discharge is 85,000mcm. With the projected 2030 climate this will increase to 111,000mcm. This corresponds to a 31% increase in the mean annual peak monthly discharge at Kratie during the wet season. Figure 3 below indicates that this increase in wet season flows is likely to affect extreme events more so than normal events. Figure 3: Historical (1951‐200) and future (2030) flood frequency for normal, significant (1 in 10 yr) and extreme (1 in 20yr) events at Kratie (Source: Eastham et al, 2008). CONCLUSIONS FOR EXTREME EVENTS In order to explore the implications of climate change for extreme events, the SEA has used the above conclusions from the CSIRO study to explore the magnitude of change that could be likely with climate change. To do this it has been assumed that the predicted 31% increase in wet season flood volumes is concentrated in an increase of extreme events. 12.2.3 B. PURPOSE & APPROACH The purpose of this calculation is to explore the implications of climate change on extreme weather in the LMB and to quantify the changes to the return periods for the events which have been used to design the 85 A ‘normal’ flood corresponds to the mean annual discharge (~13,600m3/s at Kratie) (Eastham et al, 2008). 244 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE spillways. This is an important consideration for the SEA because the risks associated with dam failure could be catastrophic for downstream reaches of the river which are some of the most densely populated regions of the basin and also play an important role in sustaining the livelihoods of riverine populations. Precedence at Yali project on the Sekong River have shown that large unannounced releases of water (in this case for provision of storage capacity for the imminent flood season) can result in loss of life and destruction of property and livelihoods. The approach taken is as follows: i. rank annual maximum series and calculate the 10yr, 100yr , 1,000yr and 10,000 yr events using the frequency factor approach as defined by Chow (1988) for the extreme value method and log pearson III method. Then compare with Adamson’s estimates for validity of the method ii. predict the impacts of CC on the annual maxima series by taking the last twenty years of historical data and projecting this data to 2030 with a 31% increase in the mean of the annual maxima between 2009‐2030 – as summarised in table 4. Figure 4: Annual maxima Series for Kratie: the blue series represents actual historical records between 1924 – 2009; the red series takes the 1990‐2009 historic data increases the value by 31% and projects it forward as the indicative 2010‐2030 series. Kratie Annual Maxima series (1924‐2009) Kratie projected 2030 series w CC 100,000 90,000 80,000 70,000 (m3/s) flow 60,000 50,000 maximum 40,000 Annual 30,000 20,000 10,000 0 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020 2030 Year 245 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE Table 4: summary of historic and projected statistics for the annual maxima series at mainstream stations: the mean of the entire series from the beginning of the historical record to 2030 typical increases by 3‐8%. The standard deviation increases by 10‐30%. Station Time period Data record Average (m3/s) standard deviation (m3/s) Chiang Saen Historical 1960‐2009 1960‐2009 10,535 2,889 CC projected 1960 – 1990‐2009 + 31% 11,297 (+7.2%) 3,217 (+11.3%) 2030 increase in mean Luang Historical 1939‐2009 1939‐2009 15,161 3,424 Prabang CC projected 1939‐ 1990‐2009 + 31% 16,109 (+6.3%) 4,498 (+31.3%) 2009 increase in mean Vientiane Historical: 1913‐2009 1913‐2009 16,717 3,286 CC projected 1913 ‐ 1990‐2009 + 31% 17,411 (+4.2%) 3,837 (+16.8) 2030 increase in mean Pakse Historical: 1923‐2009 Historical: 1923‐2009 37,479 5,658 CC projected 1923‐ 1990‐2009 + 31% 39,209 (+4.6%) 7,150 (+26.4%) 2030 increase in mean Kratie Historical: 1924‐2009 1924‐2009 51,264 8,395 CC projected 1924‐ 1990‐2009 + 31% 53,109 (+3.6%) 9,911 (+18.0%) 2030 increase in mean iii. The next step is to estimate the 10yr, 100yr, 1,000yr and 10,000yr flows using the entire time series available projected forward to 2030 iv. for convenience I have assumed that a similar increase is reflected at the other mainstream stations in a warming climate 12.2.4 COMPARISON OF HISTORICAL EXTREMES The EV frequency factor method under‐estimates the size of the return flood when compared to Adamson’s estimates and those provided by dam operators, while the LPIII is comparable to Adamson’s estimates. This becomes more of a problem for larger events, with good correlation for the one in 10yr event, while the 1 in 10,000 flood at Luang Prabang was estimated as 25,357m3/s compared to the developer estimate of 44,838m3/s. The frequency factor method is likely to be an acceptable approximation for return periods of 1,000years or less. 246 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE Comparison of 1 in 10yr flood estimated with 3 methods Comparison of 1 in 100yr flood estimated with 3 methods 70,000 80,000 60,000 70,000 60,000 50,000 50,000 40,000 40,000 30,000 Q(m3/s) Q(m3/s) 30,000 20,000 20,000 10,000 10,000 0 0 Chiang Luang Chiang Luang Vientiane Pakse Kratie Vientiane Pakse Kratie Saen Prabang Saen Prabang EV ‐ 10yr 12,252 17,137 18,670 40,842 56,254 EV ‐ 100yr 14,551 19,912 21,285 45,344 62,934 LPIII ‐ 10yr 15,625 21,614 22,287 48,226 65,602 LPIII ‐ 100yr 21,018 25,412 26,547 56,246 75,995 GV ‐ 10yr 14,000 19,800 21,100 0 0 GV ‐ 100yr 19,000 26,500 27,200 0 0 Comparison of 1 in 1,000yr flood estimated with 3 methods Comparison of 1 in 10,000yr flood estimated with 3 methods 80,000 80,000 70,000 70,000 60,000 60,000 50,000 50,000 40,000 40,000 Q(m3/s) 30,000 Q(m3/s) 30,000 20,000 20,000 10,000 10,000 0 Chiang Luang Vientiane Pakse Kratie 0 Saen Prabang Luang Chiang Saen Vientiane Pakse Kratie EV ‐ 1,000yr 16,808 22,637 23,852 49,765 69,493 Prabang GV ‐ 1,000yr 24,000 32,800 33,000 0 0 EV ‐ 10,000yr 19,061 25,357 26,414 54,177 76,040 247 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE 12.2.5 IMPACTS OF CLIMATE CHANGE Comparing the historic and future climates the following conclusions can be drawn: • The historic 100yr event is smaller than the 1 in 10yr event with the projected climate change at each station analysed. This means that an event which occurred every 100years is likely to occur more than once every 10years. • The historic 1,000yr event is comparable in size to the 1 in 100yr event at each station with climate change. This means that the 1 in 1,000yr event will become ~ 1 in 100year event. • The historic 1 in 10,000yr event is comparable to the 1 in 1,000year event with project climate at each station. This is more pronounced for downstream stations Table 5: comparison of changes to the magnitude of extreme events for the same return period EXTREME VALUE DISTRIBUTION EXTREME VALUE DISTRIBUTION Projected 2030 Return period flow (EV Historic Return period flow (EV dist) dist) with CC Station 10yr 100yr 1,000yr 10,000 10yr 100yr 1,000yr 10,000 Chiang Saen 12,252 14,551 16,808 19,061 13,209 15,769 18,282 20,790 Luang Prabang 17,137 19,912 22,637 25,357 18,783 22,362 25,876 29,384 Vientiane 18,670 21,285 23,852 26,414 19,692 22,745 25,742 28,734 Pakse 40,842 45,344 49,765 54,177 43,459 49,149 54,734 60,311 Kratie 56,254 62,934 69,493 76,040 59,000 66,886 74,629 82,358 Assuming a project design life of 100years: • Project structures designed for a 1 in 1,00 year event will see the probability of this event occurring over the design life increase from 63% to ~100% • Project structures designed for a 1 in 1,000 year event will see the probability of this event occurring over the design life increase from 10% to 63% • Project structures designed for a 1 in 10,000yr event will see the probability of this event occurring over the design life increase from 1% to 10% Table 6: Risk of failure associated with return periods for an assumed project life of 100yrs T 1 5 10 50 100 500 1,000 2,000 5,000 10,000 50,000 RISK 100.00% 100.00% 100.00% 86.74% 63.40% 18.14% 9.52% 4.88% 1.98% 1.00% 0.20% 12.2.6 THE PROBABLE MAXIMUM FLOOD & PRECIPITATION The PMP and PMF are generally used to design large water control infrastructure. The PMP provides a maximum depth of duration based on regional weather and ground cover characteristics, when coupled 248 ICEM – International Centre for Environmental Management MRC SEA | IMPACTS ASSESSMENT REPORT‐ Discussion Draft | CLIMATE CHANGE with a time distribution indicating the length of the storm event, this can then provide an estimate of the PMF using a rainfall‐runoff model (Chow et al, 1988). The PMF can be defined as the largest flood which could be expected assuming the complete coincidence of all factors that would produce the heaviest rainfall and maximum run‐off (Chow et al, 1988). The PMF method represents a deterministic approximation to extreme events compared with the probabilistic method of the return periods. The probability of occurrence for the PMP is typically not known and is often interpreted as the 1 in 500,000 year event as well as the 1 in 10,000yr event. Both the PMP and PMF methods do not take into account long term climate change, and changes to the weather pattern (e.g. increasing severity of storm events) will affect the PMP and PMF. 12.2.7 REFERENCES Adamson, P. 2009. An Assessment of the hydrology at proposed dam sites on the mainstream of the Mekong upstream of Vientiane, Report for the Ministry of Energy & Mines, Department of Electricity, Lao PDR Chow, V.T., et al. 1988. Applied Hydrology. McGraw Hill series in Water Resources and Environmental Engineering. McGraw Hill Inc. Boston, USA Eastham et al. 2008. Mekong River Basin Water Resources Assessment: Impacts of Climate Change. CSIRO National Research flagships 249 ICEM – International Centre for Environmental Management