Technical Brief: Climate Change Impacts – Implications For

TECHNICAL BRIEF

February 2021

Climate change impacts – implications for policy and practice in Tanzania’s Rufiji River Basin

Overview

This brief synthesises the results of undertaking a climate risk analysis for the Rufiji River Basin, Tanzania. The basin supports extensive socio-economic and environmental services and is targeted for major development via hydropower infrastructure and investment through the Southern Agricultural Growth Corridor of Tanzania. The implications of climate risk for development objectives that cut across the water-energy-food-environment sectors are outlined and recommendations proposed to help achieve climate resilient sustainable development. The brief is for practitioners and technical policy-makers with a detailed interest in understanding development processes and the impacts of climate change in the Rufiji River Basin. The approach is relevant for other large river basins undergoing rapid development.

Headline messages: Under current climate conditions variability of flow, without major there is considerable potential for sacrifice of hydropower. As the JNHPP Rufiji Basin development energy and irrigation expansion at is likely to generate surplus energy initially it should be possible to Major decisions require careful the full basin scale, however, there are reduce environmental and livelihoods planning; in cases involving large many trade-offs depending upon the impacts. Greater use of groundwater, investments, long life-times and extent of development. Hydropower taking into consideration observed irreversibility, there is a strong reliability in the JNHPP is affected volatility in recharge events argument for assessing resilience to by the higher projections of future could reduce trade-offs between future climate change. The Rufiji River expansion of formal and informal agriculture, energy and the Basin exemplifies this as it is targeted irrigation. Monthly and annual supply environment in dry years. for development via a major new reliability degrades with the last hydropower infrastructure project 50,000 ha of irrigation expansion, Many sub-basin scale trade-offs (the Julius Nyerere Hydropower which if unregulated could constrain associated with increasing water use Project – JNHPP) and investment additional energy generation from are not explored here. For example in agricultural value chains through the basin. local scale water scarcity (long-term the Southern Agricultural Growth Development scenarios that prioritise and seasonal) already exists in some Corridor of Tanzania (SAGCOT). energy production adversely upstream tributaries, generating affect environmental performance tensions over access and use downstream of the JNHPP, although of water, and threats to achieving part of the negative impacts can environmental flow requirements About FCFA be minimised through release rules (river flows required for supporting Future Climate for Africa (FCFA) aims to designed to replicate the natural nature) at specific locations. generate fundamentally new climate science focused on Africa, and to ensure that this science has an impact on human development across the continent. www.futureclimateafrica.org Climate impacts on Management implications Contingency plans for the JNHPP Rufiji River Basin services of climate risk should include modified operating procedures and water allocation under Analysis of historical climate Important knowledge gaps exist for both drier and wetter conditions variability shows that had the many aspects of the Rufiji River Basin. and development of a multi-agency JNHPP reservoir been built in 1900 As development proceeds there is a drought management plan for single it would have buffered dry years clear need to improve understanding and multi-year events. This would but its reliability would have been of how the basin functions. This involve sequences of decision points compromised by multi-year droughts includes improved monitoring and across years, with increasingly during the 1920s and 1930s. reporting at strategic locations and stringent restrictions on releases Future climate projections show coordinated modelling to simulate after successive years of drought. continued warming (by roughly 0.8 °C the crucial interdependencies Such plans would require careful to 1.8 °C by the 2040s) and mixed between the water-energy- analyses to identify trigger points for patterns of change in future rainfall. agriculture-environment sectors. decisions and greater cross-sectoral Most climate models (23 out of 28) The impacts are cross-cutting and coordination, particularly between project a modest to high increase therefore multi-agency coordination agencies responsible for water in annual rainfall and an increase in will be vital (e.g. through Multi- resources, energy and agriculture. variability that would be associated Sectoral Platforms), both for long- with both increased frequency of term planning and for shorter- Governance implications droughts and floods. term decisions, such as drought of climate risk The changes in Rufiji streamflow management. High level dialogue Model-based decision-support should are more pronounced, ranging from to this effect should be encouraged, be seen as part of a wider process approximately -30% to over +60%, alongside increases in the productivity of decision-making. Wider and but with a roughly even split between of land and water as promoted by deeper consultation processes allow drier and wetter futures due to the the SAGCOT initiative via improved exploration of these linkages, varying effects of higher evapotranspiration. irrigation schemes and better input management actions, and associated Daily rainfall intensity is projected to use. Priorities include focus on impacts, leading to more informed increase, and about three quarters improving local irrigation water use decision-making. For example, there of the climate models suggest an and reduction in non-recoverable are local scale trade-offs that should increase in year to year variability. irrigation losses through management and regulations. be considered alongside our basin- Uncertainty about the future climate scale analysis, such as trade-offs Given underlying questions about can be compounded by the ad hoc between irrigation expansion and the ability of climate models nature of information provision and local nature conservation values. advice about climate change risks, to confidently simulate rainfall The governance frameworks that leading to low consistency and behaviour in the region, it may be Rufiji River Basin management confusion about the reliability and too early to base expensive decisions operates within are crucial areas legitimacy of information – clear only on the basis of potential to focus on, particularly for enhanced accessible summaries with periodic impacts. Nevertheless our climate coordination and capacity to updates of climate model projections is changing and strategies need implement what will become for the basin would be useful to to be considered now to manage increasingly complex management establish a common understanding existing and future climate risks as the responses as development of the situation (for example, Conway world warms further. We therefore progresses. Political will and budget et al., 2017). recommend it would be prudent to select options that align with allocation to address the problems other considerations (such as cost highlighted above and to deliver effectiveness, desirability) and to effective and equitable policies, design and implement contingency will be critical to the viability planning for sequences of extreme of proposed developments. years and strengthened capacity for cross-sectoral management.

2 Complex impacts Agricultural Growth Corridor of Tanzania with 4.5% currently under irrigation. (SAGCOT). The SAGCOT aims to attract An estimated 2.4 billion cubic meters of development domestic and foreign investment to of water (BCM) is abstracted per year, strengthen agricultural value chains primarily for irrigation, and this is plans in the Rufiji to promote economic growth through projected to increase to 7.6 BCM per River Basin increased agricultural transformation. year to support expansion of irrigation In addition, a recent development from 110,000 ha to an upper estimate The Rufiji River Basin supplies water has been the decision in 2017 to go of 400,000 ha by 2035 (WREM for around 4.5 million people, ahead with the massive Julius Nyerere International, 2015). generates 80% of Tanzania’s Hydropower Project (JNHPP) at There are strong interdependencies hydropower and covers roughly 20% Stiegler’s gorge on the Rufiji mainstem. between critical uses of water of the country (Figure 1). The basin The cost of constructing the JNHPP throughout the basin, particularly includes several major wetland is estimated at 4.7 billion US dollars between irrigation, energy systems rich in biodiversity, formal against 2016 prices (Government of generation from hydropower and and informal irrigation schemes, Tanzania, 2016). Sustainable water requirements for environmental several hydropower reservoirs and resource management is viewed as purposes. Transparent consideration areas of high conservation value, key to its success which has profound of trade-offs between multiple including National Parks. Biennial implications for future economic and objectives can be helpful in defining flooding of the downstream delta social development trajectories, and acceptable compromise plans in river is important for maintaining deltaic as such the JNHPP reservoir can be basins characterised by conflicting lakes, wildlife, fisheries and flood considered to be a ‘high stakes’ decision. recession agriculture. Much of the performance objectives and opposing basin is targeted by the Government The basin is estimated to have two stakeholder interests. Peoplemillion in hectares the basin will(ha) be of affected medium by planning and decisions about the energy and of Tanzania for socio-economic agricultural investment required to meet development aims. There are strong development as part of the Southern interdependenciesto high potential between irrigable critical land, uses of water throughout the basin, particularly between irrigation, energy generation from hydropower and requirements for environmental purposes. Transparent consideration of trade-offs between multiple objectives can be helpful in defining acceptable compromise plans in river basins characterised by conflicting performance objectives and opposing stakeholder interests.

Figure 1: Hydrological model representation of the Rufiji River Basin system overlaid with ~9 by 9 km grid and areas identified for irrigation expansion (SAGCOT clusters) (Siderius et al., 2018). A is Great Ruaha, B is Kilombero, C is Luwegu and D is the Main Rufiji channel. Shapes of cluster areas are just indicative. Actual coverage follows the administrative boundaries.

Figure 1: Hydrological model representation of the Rufiji River Basin system overlaid with 9 by 9 km grid and areas identified for irrigation expansion (SAGCOT clusters) (Siderius et al., 2018). A is Great Ruaha, B is Kilombero, C is Luwegu and D is the Main Rufiji channel. ∼ 3 What are the main basin-scale trade-offs under different river basin development scenarios? The major trade-offs in the basin development aims comprise the extent of irrigated agriculture expansion versus the reliability of energy from the JNHPP, and their impact on environmental flows at locations with high environmental and/or economic importance. Trade-offs between water use through smallholder expansion and planned irrigation sites are also expected.

What are the main basin- optimises a combination portfolio of the natural variability of flow, with scale trade-offs under irrigation expansion, whereby only relatively small sacrifices in energy different river basin those options are implemented that generation. The reliability of monthly development scenarios? contribute to an optimum solution energy generation is more sensitive to (known as pareto optimal). The fourth environmental-oriented management The major trade-offs in the basin ‘Full’ development scenario assumes than the cumulative annual energy development aims comprise the extent the complete development of all production. Improvement in irrigation of irrigated agriculture expansion versus planned infrastructure expansion. water supply (lower deficits) can be the reliability of energy from the JNHPP, We also considered the possibility of achieved with further dams, although and their impact on environmental flows reducing the storage size of the JNHPP supply reliability degrades with the at locations with high environmental and a situation where, with better last 50,000 ha of irrigation expansion, and/or economic importance. Trade-offs management and stronger enforced which if unregulated could constrain between water use through smallholder regulations, local non-beneficial additional energy generation from the expansion and planned irrigation sites irrigation consumption and non- basin, in one case by up to 2 Twh/year. recoverable return flows can be reduced are also expected. With rapid change underway in large to become available for downstream Multiple stakeholder consultations parts of the basin, irrigation governance use (Geressu et al., 2020). were used to establish key development is challenging, however, if local non- scenarios and identify and prioritise Results show considerable potential beneficial irrigation water consumption important river basin performance exists for energy and irrigation and non-recoverable return flows are metrics to assess impacts (Geressu et al., expansion under the climate conditions reduced through better management 2020). Seven indicators were selected: of the past 30 years. Designs that and stronger enforced regulations, Energy from hydropower; annual total, prioritise energy production adversely the impact of upstream development firm (reliable) annual and firm monthly; affect environmental performance; on downstream energy production irrigation; total irrigated area, irrigation however, part of the negative and environmental conditions can water demand deficit; environment; impacts can be minimised through be minimized (Geressu et al., 2020). area flooded by the JNHPP and river release rules designed to replicate flow disruption downstream in the lower Rufiji. A basin hydrological model was coupled with a water resource system model that simulates the operation and effects of dams and irrigation in the basin (Geressu et al., 2020). Many thousands of simulations were used to test different combinations of options (e.g., new dams and irrigation developments) and their management (e.g., by varying reservoir release policy) to identify options that perform well across the different performance indicators. The four development scenarios considered in our case study were informed by published government plans and workshop discussions about different trajectories of basin development. The first one considered the ‘Current’ river basin and the second the addition of the JNHPP. A third ‘Synergistic’ scenario

4 Box 1. Land use futures futures suggest a range of tensions over (mainly rice, maize, fruits and for Kilombero co-created land use are likely to increase or appear coconuts) to cash crop production through participatory during the next fifty years. They include: (mainly sugar cane, teak and cocoa) scenario planning Recent in-migration from pastoralists with associated mechanisation and (Thorn et al., in review) has led to land scarcity and labour trade-offs, and agrochemical encroachment of wetlands and Game seepage into rivers; Four different land use scenarios were Protected Areas and impacts on water Conflicts from local corporates developed with multiple stakeholders courses with likely future knock-on withdrawing from economies, across the Kilombero catchment of effects on agriculture, fishing and not meeting supply chain the Rufiji River Basin in 2019 and hydroelectric power; due diligence and a lack of 2020. These land use futures can be Conflicts between wildlife transparency of spending of used to explore drivers of change conservation managers and public infrastructure funds; and envision plausible pathways and infrastructural (especially road) Conflicts prior to general elections impacts of different development developers over the location of arising from political interference agendas and horizons. Potential land transport routes that obstruct key that cause tension around land, use and land cover changes were migration routes of elephants and livelihoods and politics with simulated for the years 2030 and other mammals; and with pastoralists a surge of encroachments; 2063 and compared against the year being resettled from Ramsar wetlands Conflicts associated with 2019; these future years were chosen sites or farmers being resettled from cultural change, assimilation to resonate with the Sustainable protected areas. Success will largely and gender equity; Development Goals and the ‘Africa depend on adequate compensation, 2063’ Development Agenda of the Conflicts related to the illegal engagement and ensuring conflicts African Union. This analysis highlights extraction of fuelwood, poaching, do not spill over into other areas; the importance of considering and human wildlife conflict the interaction of future land use Conflicts related to land use planning especially adjacent to protected management decisions and resulting process in an attempt to clarify areas or wildlife corridors; and land cover changes to mitigate some ambiguous boundaries, depending Conflicts between land use of the impacts of potential climate on enforcement and the negotiation especially between urban and change, particularly around regulating power of local communities; agricultural land with no spatial increasing rainfall variability through Conflicts between corporate planning and social services catchment forest, conservation tillage and smallholder farms, and the including health, education, and riparian buffer zones. The land use transition from food crop production housing and infrastructure.

Sub-basin scale the impacts of afforestation in 2005; Walsh, 2012). This has resulted environmental impacts upstream catchments and stakeholder in competing explanations between perspectives on development climate, upstream resource use and There are many sub-basin scale trajectories in sub-catchments management, of low levels in the trade-offs associated with increasing (development clusters in the SAGCOT, Mtera reservoir that caused electricity water use for agriculture, with impacts see DCP and Box 1). Furthermore, shortages during the early 1990s and on the natural environment at ongoing changes in the basin have the roles of large, centrally controlled key locations with high ecological been associated with important points irrigation schemes and smallholder value. While assessment of such of contestation such as tensions in farmers (Lankford et al., 2004). impacts is beyond the scope of this the Great Ruaha sub-catchment over basin-scale study, the Development smallholder agriculture and pastoralists, Corridors Partnership project has irrigation expansion, land-grabbing explored several examples including and conservation (Kashaigili et al.,

5 Figure 2 a.) Annual rainfall (October – September period) for the Rufiji River Basin (source: CenTrends), with years with modest to strong El Niño/La Nina and with strong positive/negative IOD highlighted. b.) Simulated mean annual Rufiji inflows and outflows; c.) simulated monthly live storage of JNHPP reservoir (assuming it was built in 1900). Risk of failure, i.e., not being able to release sufficient water to maintain firm energy flow is indicated by the purple bars, while green dots highlight years with sufficient release of water to satisfy downstream flood requirements of the delta ecosystem (adapted from Siderius et al., in press).

Securing investments in the irreversibility, there is a strong argument How has past climate variability face of climate change for climate risk assessment – damages affected the basin? and losses from new combinations Analysis of recent climate variability Rapid development in the Rufiji River of extreme weather are an increasing and its effects on water resources Basin is occurring against a back- problem. The following sections set out can provide helpful insight about the drop of climate change. As the world key findings from our work to assess types of problems that arise and how continues to warm so do eastern and climate risk and identify responses to manage them. Recent climate is southern Africa, bringing changes in suitable for maintaining sustainable described in detail in an earlier Country the climate patterns people are familiar development for different stakeholders Brief (Conway et al., 2017). A clear with and disruption to livelihoods in the basin. warming trend is apparent in annual and infrastructure. In cases involving temperature (roughly 0.03°C per year). large investments, long lifetimes and

6 Rainfall is highly seasonal, averaging sequences of wet and dry years (see primarily for hydropower purposes. In our 935mm per year with a large gradient Figure 2a). Storage in the JNHPP buffers simulation the peak flow threshold of across the basin, from 500mm per year the effects of individual dry years, more than 2500m3 during a whole month (northern part of the basin) to more however, multi-year dry conditions (Figure 2b and 2c) would reduce the than 1500mm per year (central part of would have led to the JNHPP – frequency of delta flooding from one in the basin, Kilombero valley, Figure 1). assuming it was built and operated two to less than one in ten years, with long Between 1981 and 2016 there were to prioritise firm (reliable) electricity periods of insufficient flows. This would areas of modest drying in northern production and no contingency actions impact the delta ecosystem, fisheries and parts of the Basin (up to around 2mm/ were implemented – failing to meet farming; however, it is possible that the year) and areas of modest wetting in its potential firm energy level for JNHPP dam could be operated to mitigate the central part of the basin, particularly consecutive years on several occasions this risk but at the expense of reliable the Kilombero valley and Lower Rufiji (Figure 2b and 2c). energy production (Siderius et al., in press; (around -2 to -4mm/year). A prolonged Geresu et al., 2020). The second half of the 20th century dry period occurred between 1906/07 recorded wetter periods especially in The potential impacts of future and 1929/30 with just six years in the 1960s, similar to much of East Africa. 23 wetter than average. Since a very climate change The simulation shows that under these wet year in 1997/1998 (a major El We reviewed the range of climate conditions the JNHPP would have just Niño and Indian Ocean Dipole event) projections available from the leading managed to maintain the firm energy rainfall over whole the basin has been source of climate model results and output level due to its large storage generally lower than the long-term whilst continued warming is highly size, but only if upstream irrigation average (Figure 2). likely (roughly 0.8 °C to 1.8 °C by the expansion was managed to ensure 2040s) projections of future rainfall Using a hydrological model of the recovery of irrigation water return averaged across Tanzania are mixed: Rufiji River Basin (Siderius et al., 2018), flows. Uncontrolled upstream irrigation out of 34 models used in the last IPCC a simple reservoir simulation model expansion and greater reuse of return report roughly one third project lower and gridded climate data products, flows by smallholder farmers is ongoing, rainfall and two thirds higher rainfall we examined the impact of long-term which would put greater pressure on the (Conway et al., 2017). climate variability (since 1900) on performance of the JNHPP downstream. the JNHPP (Siderius et al., in press). The range of rainfall change across The present relatively undisturbed natural Historical simulations driven by observed the 34 models is fairly modest, with 20 flow regime in the Rufiji comprises climate since 1900 represent a ‘what-if models projecting changes of less than biennial bank overflows which rejuvenate scenario’ of how the reservoir system +/-5% by the 2040s. Changes in daily one of the world’s largest deltaic wetland would behave, as if the hydropower rainfall suggest more variable conditions, systems in the Nyerere National Park and planned irrigation expansion had with both higher likelihood of dry spells (formerly the Selous Game Reserve) and been present from 1900 onwards. and a higher likelihood of intense rainfall support downstream flood recession Rainfall variability causes high variability events that are likely to increase the irrigation. The JNHPP dam will alter in stream flow with persistence of frequency and intensity of flooding. this pattern, particularly if operated

7 28) models project a modest to high increase in annual rainfall; the rainfall change for 2021- 2050 compared to the near-present day (or baseline) period of 1980-2010 ranges between - 10% to +30%. This climate uncertainty is amplified and modified by hydrology (compare Figures 3a and 3b); the largest changes in runoff are more pronounced, ranging from Figure 3 (a) Projectedapproximately change -in30% rainfall, to over (b) river +60%, basin and runoff while at thethe majorityJNHPP site of near models the outlet project with an increase in 28 different climaterainfall, models.the impacts on runoff are more evenly distributed between drier and wetter futures (12 models simulate reduced runoff). Increased transpiration by plants and crops due to higher temperatures can offset a projected increase in rainfall in some cases.

Figure 3 (a) Projected change in rainfall, (b) river basin runoff at the JNHPP site near the outlet with 28 different climate models.

Impacts of climate change on river basin performance indicators Simulated risk of failure to achieve performance indicators across the water-energy-food sectors are shown in Table 1 for past and future climate (Siderius et al., in review). Under near present-day climate (1981-2010), the risk of failure with the JNHPP assumed built,

8 Figure 3 shows for the 2040s period Regarding future risk, our analysis Positive impacts occur for the rainfall change for the Rufiji River Basin demonstrates considerable uncertainty environmental flow indicator, and impacts on the main river flows (Table 1 and Figure 4). For the majority of with increased variability in rainfall using an equal weighting of 28 climate projections, with this hydrological model and runoff increasing the chance of models, based on their projections of and at this scale of analysis, the risk of high releases during the wet season, changes in temperature and rainfall hydropower failure increases. Design though considerable risk remains. (Kolusu et al., in review; Siderius et al., characteristics of the JNHPP may be Specific adaptive environmental flow 2021). Most (23 out of 28) models project influenced by the limited observational management measures, a topic worthy a modest to high increase in annual river flow records of the late 1950s, 1960s of further research and development, rainfall; the rainfall change for 2021- and early 1970s, a relatively wet period will be necessary to reduce the expected 2050 compared to the near-present day (Figure 2), and climate projections with negative impacts, which will involve (or baseline) period of 1980-2010 ranges drier conditions increase the risk of failure. a trade-off between total energy between -10% to +30%. This climate However, as many model projections production and environmental flows. uncertainty is amplified and modified by of drying also exhibit high variability Upstream irrigation water supply deficits hydrology (compare Figures 3a and 3b); in rainfall, wet years alternate with dry in the basin might reduce in future with the largest changes in runoff are more years and add to live storage, thereby high model agreement for slightly wetter pronounced, ranging from approximately keeping hydropower risk of failure in future conditions in the mountainous -30% to over +60%, and while the most projections at 15% or below. For a areas to the west of the basin. majority of models project an increase subset of wet climate projections the risk in rainfall, the impacts on runoff are with regards to firm energy decreases more evenly distributed between drier drastically in the JNHPP hydropower and wetter futures (12 models simulate system (Siderius et al., in press). reduced runoff). Increased transpiration by plants and crops due to higher temperatures can offset a projected increase in rainfall in some cases. Table 1 Risk of failure (in %) in three performance indicators for different periods in the Rufiji River Basin. Future risk is the multi Impacts of climate change on river climate model average. Note: risk is based on hypothetical simulations basin performance indicators which include planned investments in irrigation and hydropower that Simulated risk of failure to achieve are yet to be implemented. The results are therefore illustrative and performance indicators across the should be interpreted with care. (Siderius et al., in press.) water-energy-food sectors are shown in Table 1 for past and future climate Rufiji (Siderius et al., in press). Under near Period Hydropower E - Flow Irrigation present-day climate (1981-2010), Historic risk 1900 - 2009 12 78 43 the risk of failure with the JNHPP assumed built, irrigation expanded, 1900 - 1929 38 79 51 and no adaptive management applied 1910 - 1939 30 80 48 is already substantial. Using this 1920 - 1949 10 80 44 particular indicator for ecosystem 1930 - 1959 3 87 43 services in the Rufiji, environmental flow failure rate could be as high as ~85%. 1940 - 1969 3 73 41 For irrigated agriculture in upstream 1950 - 1979 0 67 41 rice producing areas in the Rufiji River 1960 - 1989 0 67 39 Basin performance shows a failure rate >40%. Here, irrigation is vulnerable to 1970 - 1999 0 87 40 climate variability due to lack of storage. Present risk 1980 - 2009 3 87 41 In contrast, firm-level hydropower Future risk; mean (SD)Ŧ 2020 - 2050 4 (7) 57 (28) 22 (7) requirements could be met reliably Ŧ under present conditions and risk of Mean risk and standard deviation of 29 bias-corrected climate projections failure would be low.

9 The full climate risk profile is important Figure 4 Climate change impacts on failure rates in three Rufiji River in advising policy makers and guiding Basin performance indicators in three sectors, summarizing reliability further research; under this model of infrastructure under current baseline (1970-2010) and future climate setup the most serious potential (2020-2050), with projected change in variability. Size of circles and hydropower risk in the Rufiji River number (plotted if not overlapped by a circle) represent the percentage Basin (e.g., over 35%) occurs with of climate model projections in this category of risk (in this case a just three outlier models, which, total of 24 models). ‘Hydro’ indicates the risk of not meeting firm depending on stakeholder risk appetite characterised by a concentration of models around a certain risk or by an even spread from energy requirements; ‘E-flow’ indicates the risk of not meeting bi- could be further scrutinized for their low to high risk,annual such flooding as for the requirements environmental in the flow Rufiji indicators, River Basin, with and ‘Irrigation’uncertainty less likelyrepresentation to of regional climate drivers be easily constrained.indicates risk of not meeting monthly demand, given the assumptions and teleconnections and discounted if underpinning our scenarios. (Siderius et al., in press). found unsatisfactory, to avoid making expensive modifications on the basis of unreliable information. Other risk profiles are either characterised by a concentration of models around a certain risk or by an even spread from low to high risk, such as for the environmental flow indicators, with uncertainty less likely to be easily constrained. Is it possible to reduce uncertainty due to climate projections? The uncertainty created by having many different projections of rainfall can be a challenge to decision-making. There is no established method for deciding upon which climate models to use for impact and risk assessment, although it is widely agreed that using only one model (or the average of many) and ignoring the range suggested by other available models is poor practice. Generally, the accepted source is the CMIP5 ensemble of models compiled for the IPCC Fifth Assessment (now updated to CMIP6 with results just beginning to appear). While there are many options available for selecting models, there is limited guidance and many questions Figure 4 Climate change impacts on failure rates in three Rufiji River Basin performancearise, for example, should we use: all indicators in three sectors, summarizing reliability of infrastructure under current baselineavailable models? Early versions and (1970-2010) and future climate (2020-2050), with projected change in variability. Sizelater of versions of models? Exclude some circles and number (plotted if not overlapped by a circle) represent the percentage of climatemodels deemed to be poor performers model projections in this category of risk (in this case a total of 24 models). ‘Hydro’ indicatesor weight them less? (Kolusu et al., 2021; Siderius et al., in press). the risk of not meeting firm energy requirements; ‘E-flow’ indicates the risk of not meeting There are of course other practical bi-annual flooding requirements in the Rufiji basin, and ‘Irrigation’ indicates risk of notconsiderations such as time, expertise, meeting monthly demand. and costs associated with applying model selection. Is it possible to reduce uncertainty due to climate projections? The uncertainty created by having many different projections of rainfall can be a challenge to decision-making. There is no established method for deciding upon10 which climate models to use for impact and risk assessment, although it is widely agreed that using only one model (or the average of many) and ignoring the range suggested by other available models is poor practice. Generally, the accepted source is the CMIP5 ensemble of models compiled for the IPCC Fifth Assessment (now updated to CMIP6 with results just beginning to appear). While there are many options available for selecting models, there is limited guidance and many questions arise, for example, should we use: all available models? Early versions and later

We tried one approach to try to Given the overriding importance of We presented risk without considering narrow the range; to assess climate Kilombero streamflow to Rufiji flows adaptation. Through adaptive model realism (or skill) in simulating and the rapid development of this valley, management and well-designed key features of African climate and better understanding of its wetland reservoir operating rules and improved use this to rank (give different levels systems and the hydrological and irrigation practices, some of the risks, of influence to models with differing wider impacts of land conversion and e.g. the impact of the JNHPP reservoir levels of skill) model selections (sub- agricultural management is crucial. on Rufiji’s downstream delta ecosystem, samples) and exclude the weakest could potentially be mitigated. There are assumptions and values performing models, from a sample of 24 incorporated within any analysis of climate models available from CMIP5. performance metrics. Our selection Management and We considered three methods of model of performance indicators is heavily governance context weighting, noting that others could constrained by data availability and be used. We found that in our example practical concerns about making the Alongside our work on water resources the model weighting approaches do analysis manageable and communicable modelling and climate change impacts, not greatly reduce the inter-model to broad audiences. For comprehensive we have examined the institutional uncertainty, but the analysis gave basin management a much larger suite and governance dimensions across the insights into the causes of uncertainty of performance indicators is necessary. water-energy-agriculture sectors in (Kolusu et al., in press; Siderius et al., Tanzania, and how climate change is 2021). Of note is that there is more We restrict our analysis of environmental being absorbed into policy processes agreement on the projected change flows to two indicators at one location. (Pardoe et al., 2017, 2020; Geressu et in future rainfall variability, with about However, we note that environmental al., 2020). At the national level water, three quarters of the climate models flows are a multi-faceted concept that energy, agriculture and environment suggesting an increase in year-to-year includes other aspects such as (peak) are divided into separate government variability, however, despite advances in flow duration and water quality. There ministries in Tanzania; the Ministry of understanding plausible mechanisms of are many other locations where certain Water (MoW), the Ministry of Energy, future climate change, there is still much streamflow characteristics are critical Ministry of Minerals, the Ministry of uncertainty on how exactly this will for environmental purposes and require Agriculture (MoA) and the Ministry affect climate variability over the region. further consideration. of Natural Resources and Tourism While irrigation and land use change (MNRT). Irrigation has formerly Addressing key are evolving rapidly in parts of been located within a Ministry of knowledge gaps the basin, government targets are Agriculture and Irrigation. Cross-sectoral likely to be highly optimistic, given collaboration, which is crucial to Important knowledge gaps exist for experience before and elsewhere in effective implementation, is not strongly many aspects of the Rufiji River Basin. sub-Saharan Africa. Our Rufiji River evident. While national policies and As development proceeds there is a clear Basin development scenarios lie at the plans continue to call for cross-sectoral need to improve understanding of how upper end of the targets and as such working, in practice collaboration the basin functions, including the crucial reflect a highly optimistic outcome is limited and largely confined to ad interdependencies between the water- (in terms of meeting government hoc projects and activities. Barriers energy-agriculture-environment sectors. targets). More consultation is required include institutional structures, resource constraints that dis-incentivise In the modelling we have had to make to verify ongoing rates of change collaboration due to issues around cost a number of assumptions due to the (satellite analysis can also help) and to recovery, and a need to protect roles and complexity of the basin and data seek views on alternative scenarios of responsibilities to ensure future budgets. sparsity. A priority for future water basin development and their relative resources management is to rehabilitate merits for different stakeholders and or establish and maintain gauging sites the environment. at critical points in the basin, particularly on the Rufiji main channel and the Kilombero and Luwegu tributaries that supply the bulk of the water to the JNHPP.

11 Since coming to office in 2015, President Change Strategy (NCCS) (URT, 2012), collaborative and coordinated efforts Dr John P.J. Magufuli has prioritised which guides the integration of climate in practice. For example, currently the domestic economic growth through change in sectoral policies and plans. MoW and the Tanzania Meteorological emphasis on industrialisation, as The NCCS draws heavily on the National Agency (TMA) incur costs to collect data outlined in various 5-year plans. The Vice Adaptation Plan of Action (NAPA, URT, and whilst the MoW usually provides this President’s Office holds two mechanisms 2007), which includes plans for climate freely, TMA charges fees which can stall for managing environmental issues change adaptation for various sectors, agreements on provision of data to other and climate change: the Division of including water, agriculture and energy. parties (Pardoe et al., 2017). A platform Environment (DoE); and the National However, overall, the NAPA tends to for sharing data among government Environment Management Council emphasise vertical integration and departments would help foster (NEMC). Tanzania has a National Climate major gaps remain in cross-sectoral collaboration and promote efficiency.

12 At the river basin level our analysis coordinated between district and village Reportedly, a high-level dialogue started highlights important interdependencies; level. The Water Resources Management in April 2019 at the Vice President Office upstream – downstream and cross- Act No 9, of 2009 enshrines into law initiative between the ministries of sector. Balanced development requires formal water management in Tanzania Energy, Natural Resources and Tourism, governance and management at and the water allocation is managed by Agriculture and Water to discuss the the development corridor (SAGCOT) the Rufiji Basin Water Board, but it has issue and propose a solution (Geressu et and basin scale. Like climate change, limited capacity to enforce regulation al., 2020). This, coupled with increased a shared vision of basin development of water permits. Any water abstraction productivity of land as promoted by the needs to achieve internal recognition without a permit is defined as illegal but SAGCOT initiative via improved irrigation and ownership by relevant agencies in practice, many smallholder farmers schemes and better input use, could be to become legitimate and move abstract with no permit. Water User an avenue for greater water conservation to implementation. Associations (WUAs) are to support for downstream energy generation. the formalization of water access for Relevant government bodies include Moving beyond the Rufiji River Basin smallholder farmers but have so far led the Rufiji Basin Water Board within scale, if hydropower dams can be to mixed results as the poorest have the MoW, the Ministry of Energy and integrated in regional power grids, been found to leave some farmers the Ministry of Minerals regulates the it could reduce systemic risk of drought behind (Richards, 2019). operations of the Tanzania Electric impacts in the basin itself, by offsetting Supply Company (TANESCO) that While the extent of informal irrigation with hydropower in other regions manages the hydropower dams, and expansion alongside the planned (with different rainfall variability). the MoA and the Ministry of Finance schemes in the future is unclear, it is an This also offers opportunities; with and Planning are also important. A Rufiji ongoing process that deserves more Africa being increasingly connected Basin Development Authority (RUBADA) attention. Any irrigation expansion through new infrastructure corridors was dissolved around 2016. Past events beyond what is already considered such as the SAGCOT, trade can in the basin have highlighted issues is a concern, given ongoing changes contribute to increased income, with coordination of dam releases in the basin are already associated food and energy security. contributing to reduced electricity with important points of contestation. Finally, complementary options, such generation and limited coordination For example, at various times tensions as solar, thermal or wind power, which between water resources and and competing explanations have played can be expanded incrementally, are energy sectors. out in the Great Ruaha sub-catchment rapidly becoming cost-competitive and over the actions and impacts of Planned irrigation in the Rufiji River should be considered alongside an open smallholder agriculture and pastoralists, Basin is set and managed by the National consultation and assessment process for irrigation expansion, land-grabbing Irrigation Commission under the framing major infrastructure decisions. and conservation. of the National Irrigation Masterplan and supported by aid‐funded feasibility Development and management studies. Autonomous irrigation challenges cut across all these bodies, development by smallholder farmers is they all affect and are affected by a land use change driver where practical development throughout the basin. policy influence is more uncertain and is With the construction of the JNHPP and currently expanding in the wetlands of if SAGCOT (or other processes) stimulate the Kilombero sub-catchment (Figure 1; extensive agricultural intensification Box 1), the largest contributor to the then mechanisms for communication Rufiji main stream flows. In practice, and coordination will be increasingly enforcement of village land use plans, important; both for long-term planning framed by Village Land Use Plans drawn and for shorter-term decisions, such as by the Ministry of Lands, Housing and drought management. Human settlements, is weak and poorly

13 This Brief draws heavily on the following papers and briefs;

Geressu, R., Siderius, C., Harou, J., Kashaigili, J., Pettinotti, L. and Conway, D. (2020) Assessing river basin development given water-energy-food-environment interdependencies. Earth’s Future, 7, e2019EF001464. https://doi.org/10.1029/2019EF001464 Kolusu, S.R, Siderius, C., Todd, M., Bhave, A., Conway, D., James, R., Washington, R., Geressu, R., Harou, J. and Kashaigili, J. (2021) Sensitivity of projected climate impacts to climate model weighting: Multi-sector analysis in eastern Africa. Climatic Change, 164:36. https://doi.org/10.1007/s10584-021-02991-8 Pardoe, J., Conway, D., Namaganda, E., Vincent, K., Dougill, A. and K., Kashaigili, J. (2017) Climate change and the water-energy- food nexus: Insights from policy and practice in Tanzania. Climate Policy. www.tandfonline.com/doi/pdf/10.1080/14693062.2017.1386082 Siderius, C., Biemans, H., Kashaigili, J. and Conway, D. (2018) Going local; regionalizing and evaluating a global hydrological model's simulation of river flows in a medium-sized East African basin. Journal of Hydrology: Regional Studies 19 (2018) 349–364. https://doi.org/10.1016/j.ejrh.2018.10.007 Siderius, C., Kolusu, S., Todd, M., Bhave, A., Dougill, A., Reason, C., Mkwambisi, D., Kashaigili, J., Pardoe, J., Harou, J., Vincent, K., Hart, N., James, R., Washington, R., Gerussu, R. and Conway, D. (in press) Climate variability impacts water-energy-food infrastructure performance in Eastern Africa. One Earth. Siderius, C., Geressu, R., Todd, M.C., Kolusu, S.R., Harou, J.J., Kashaigili, J.J. and Conway, D. (2021) High stakes decisions under uncertainty – dams, development and climate change in the Rufiji River Basin pp 93-113. In Conway, D. and Vincent, K. (eds) Climate Risk in Africa: Adaptation and Resilience. Palgrave, Macmillan. www.palgrave.com/gp/book/9783030611590

Briefs;

UMFULA (2019) How to plan for an uncertain climate future in central and southern Africa – key findings from UMFULA on Malawi and Tanzania. FCFA Brief. 28pp. Cape Town: CDKN. Conway, D., Geressu, R, Harou, J., Kashaigili, J., Pettinotti, L. and Siderius, C. (2019). Designing a process for assessing climate resilience in Tanzania’s Rufiji River Basin. FCFA Country Brief. 8pp. Cape Town: CDKN. Conway, D., Vincent, K., Grainger, S., Archer, E.A. and Pardoe, J. (2017) How to understand and interpret global climate model results. FCFA Programme Brief. 8pp. Conway, D., Mittal, N., Archer, E.A., Pardoe, J., Todd, M., Vincent, K. and Washington, R. (2017) Future climate projections for Tanzania. FCFA Programme Country Summary. 2pp. Conway, D., Mittal, N., Archer, E.A., Pardoe, J., Todd, M., Vincent, K. and Washington, R. (2017) Future climate projections for Tanzania. FCFA Programme Country Climate Brief. 12pp.

14 Other references cited

Government of Tanzania (2016) Power System Master Plan 2016 Update. Dar es Salaam: Ministry of Energy and Minerals. Kashaigili, J. J., Kadigi, R. M. J., Lankford, B. A., Mahoo, H. F., & Mashauri, D. A. (2005). Environmental flows allocation in river basins: Exploring allocation challenges and options in the Great Ruaha River catchment in Tanzania. Physics and Chemistry of the Earth, 30 (11-16 SPEC. ISS.), 689–697. https://doi.org/10.1016/j.pce.2005.08.009 Lankford, B. A., Tumbo, S., & Rajabu, K. (2009). Water competition, variability and river basin governance: A critical analysis of the great Ruaha River, Tanzania. In River Basin Trajectories: Societies, Environments and Development (pp. 171–195). Pardoe, J., Vincent, K., Conway, D., Archer, E., Dougill, A., Mkwambisi, D. and Tembo-Nhlema, D. (2020) Evolution of national climate adaptation agendas in Malawi, Tanzania and Zambia: the role of national leadership and international donors. Regional Environmental Change 20:118. https://doi.org/10.1007/s10113-020-01693-8 Richards, N. (2019) Water users associations in Tanzania: Local governance for whom? Water (Switzerland), 11(10), 2178. https://doi.org/10.3390/w11102178 URT – United Republic of Tanzania (2007) National adaptation programme of action (NAPA). Dar es Salaam: Vice President’s Office, Division of Environment. URT – United Republic of Tanzania (2012) National climate change strategy. Dar es Salaam: Vice President’s Office, Division of Environment. Walsh, M. (2012). The not‐so‐Great Ruaha and hidden histories of an environmental panic in Tanzania. Journal of Eastern Africa Studies, 6, 303–335. WREM International Inc. (2015). Rufiji IWRMDP final report, volume I: Rufiji IWRMD plan. Report prepared for the United Republic of Tanzania, Ministry of Water. Atlanta, GA: WREM International Inc.

15 About Future Climate for Africa

Future Climate for Africa (FCFA) aims to generate fundamentally new climate science focused on Africa, and to ensure that this science has an impact on human development across the continent.

UMFULA and Development Corridors Partnership authors: Declan Conway1, Christian Siderius1, Robel Geressu2, Japhet Kashaigili3, Jessica Thorn4, Seshagiri Rao Kolusu5, Laetitia Pettinotti6 Martin Todd5, Robert Marchant4 and Julian Harou2 1 Grantham Research Institute on Climate Change and the Environment (London School of Economics and Political Science), 2 University of Manchester-UK, 3 Sokoine University of Agriculture-Tanzania, 4 York Institute of Tropical Ecosystems, University of York, UK (KITE), 5 University of Sussex, UK. 6 Overseas Development Institute-UK.

Please cite as: Conway, D., Siderius, C., Geressu, R., Kashaigili, J., Thorn, J., Kolusu, S., Pettinotti, L., Todd, M., Marchant, R. and Harou, J. (2021) Climate Change Impacts – Implications for Policy and Practice in Tanzania’s Rufiji River Basin. FCFA Technical Brief. 16pp. Cape Town: CDKN.

We thank Diego Juffe Bignoli for the four photos which show scenes from the Ihemi development cluster of the SAGCOT.

For further information please contact: Professor Declan Conway, principal investigator ([email protected]) or Professor Japhet Kashaigili (in Tanzania) ([email protected] or +255 754 207117) or visit http://futureclimateafrica.org/project/umfula/. UMFULA is part of the Future Climate For Africa programme, funded by the UK Department for International Development and Natural Environment Research Council. We also acknowledge funding from the UK Research and Innovation’s Global Challenges Research Fund (UKRI GCRF) through the Development Corridors Partnership project (project number: ES/P011500/1). https://developmentcorridors.org.

Partner:

Funded by: Photos by Diego Juffe Bignoli showing scenes from the Ihemi development cluster of the SAGCOT. cluster the Ihemi development from scenes showing Bignoli Diego Juffe by Photos

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