Xiaolangdi Multipurpose/ Ressetlement Proj'ect EA Category a Public Disclosure Authorized Xiaolangdimultipurpose Dam Project Februay 1993 Public Disclosure Authorized
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Environmental Assessment/Analysis Reports _______ Public Disclosure Authorized Report E0030 China - Public Disclosure Authorized Xiaolangdi Multipurpose/ Ressetlement Proj'ect EA Category A Public Disclosure Authorized XiaolangdiMultipurpose Dam Project Februay 1993 Public Disclosure Authorized This report has been prepared by the Borrower or its Consultant XIAOLANCDIMULTIPURPOSE PROJECT ENVIRONMENTALASSESSMENT SUMMARY (SUMMARYOF EIA EXECUTIVESUMMARY) 1. INTRODUCTION 1.1 The Xiaolangdi Project is a uajor multipurpose dam and reservoir project which has been the subject of environmental assessment extending over six years by a team from the Yellow River Conservancy Commission (YRCC) supported by 88 Chinese experts and also by an International Panel of Experts appointed to make inputs on dam design and safety factors. The results of this work are reported in 22 specialist reports and an EA Report of considerable length and complexity. The EA Executive Swumzary (attached), in itself is a substantial document. 1.2 This covering note has been prepared to provide a. focus on the key findings of the EA and to point to those sections of the EA Executive Summary where further relevant informationcan be found. 2. PROJECT OBJECTIVESAND DESCRIPTION Objectives and Background 2.1 The primary objectivesof the project are: (a) flood control in the Yellow River; (b) sediment control; (c) power production;and, (d) water supply for irrigation, urban and industrial development. Supplementary objectives include eco-restoration in the reservoir area and promotion of aquaculture. 2.2 The Yellow River bas the highest sediment concentration of all major rivers of the world because of the higb and continuing massive erosion of the Loess Plateau upstream of the Project area. Downstream silt deposition has progressively raised the river bed and greatly increased the hazard of flooding in the highly developed downstream region, which has been a very serious problem for over 2,000 years. 2.3 A system of dikes and training works along both banks has been developed for flood protection; however the dike system is very precarious because the river bed is raised 3-10 meters above the surrounding urban and agricultural areas. It is increasingly difficult, dangerous and costly to continua raising the dikes because of foundation and structural safety problems. Prior to the 1950s, there were several breaches in the dykes and in the 1938 breach 890,000 people were killed and 12.5 million were made homeless. 2.4 The project will significantly reduce this problem and provide safety, economic and social benefits to an estimated 100 aillion people, mostly farmers living in the lower Yellow River basin. It will achieve this by increasing the level of flood protection for the 97 million people living outside the dykes from 1-in-60 years, at present, to 1-in-1,000years after completion. However, there are at present three million people living within the dykes and downstream flood detentionbasins for whou the present level of protection is only against 1-in-2 year floods. The dam will increase their -2- protection to between l-in-7 years and 1-in-50 years. People have been living inside the dykes for 500 years and have limited options to migrate elsewhere since the population density is 800/km2 in most areas within a 1,500 km radius. Project Description 2.5 Design and Construction. The damsite is located on the Yellow River. approximately 40 km upstream of the city of Luoyang, Henan Province. The site is 130 km downstream from the Sanmenxia Dam, and 115 km upstream from the Beijing-Guangzhou Railway Bridge at Zhengzhou. 2.6 The project consists of the dam. flood release and silt discharge structures, and water diversion and electricity-generating structures. The dam is a 154 m high rock-filled structure with irner blanket and inclined loam core. Total reservoir capacity is approximately 12.65 billion en. Fifteen tunnels will be developed: six for flood release; three for silt discharge; and, six diversions for electricity generation. All 15 tunnels are located in the rock mass of the river banks. The tunnel intakes are combined in a single intake tower. A normal spillway and an emergency spillway are also located on the left bank. 2.7. The maximum dischargecapacity of the reservoir is 17.000 3/~s. The hydroelectric plant is subterranean and bas an installed capacity of 1,800 M1 with a long-term average energy output of 5.4 billion kWh. Total investment required from all sources for the project is in the vicinity of Y 11 billion. 2.8 The construction period is eight years with river closure occurring at the end of the flood season in the fourth construction year. The flood control objective will be achieved in the seventh year. Two turbine units will operate during the seventh year, and four additional units will enter operation in the following year. QRerat£ions 2.9 The reservoir is designed to be operated in a unique way to manage the special silt problem mentioned above. The reservoir will be operated on an annual cycle designed for Ostoring clear and discharging suddy' water. Beginning in early July, the reservoir water level will be drawn down and regulated to discharge silt-laden floodwaters until late September. From October to June, the water entering the reservoir, containing a relatively low sediment load, will be stored and regulated for irrigation, water supply, electricity generation and control of river ice-jamming which is another serious hazard closely related to flood control. 2.10 To optimize sediment deposition in the reservoir, the water level will be regulated initially at the minimum head for effective power production and then increased at a rate of 3 m per year. This will trap most of the coarse sand, while most of the fine silt will be discharged. After about 20 years of operation, the design sediment dead storage capacity will be filled. The water level will then be dropped during the course of each year -3- to flush out accumulatedsediments, and therebymaintain the reservoir live storage of 5.1 billion m3. The high flushing flow volumes of 20 to 24 billion m3 per year will *limit downstream sedimetitation so most of the silt will be discharged to the sea. 2.11 The 5.1 billion m' effectivestorage of the reservoir will be used primarily for flood control and regulatingwater and silt. The reservoir can control floods with a return frequency of 1,000 years magnitude, and limit the flow in the lower reaches of the river to within the control capacity of the existing dikes. By using reservoir storage effectively, the large runoff now being lost to the sea during the flood se&son may be used for irrigation and other beneficial uses, especially to meet urban and industrial growth needs. Over the first 50 years of operation, it is estimated that the Xiaolangdi Reservoirvill reduce downstreamsiltation by approximately7.8 billion tons and eliminate tne need for further raising of the dikes. 2.12 Section 2.B of the Executive Summary provides further information on design and operation of the dam. 3. PROJECT BENEFITS 3.1 Flood and Ice Control. The major benefit is that the project will achieve effective control of frequent serious and dangerous flooding of the entire lower basin occupied by some 100 million people. This critical need has existed for centuries, and has progressively become more and more critical as population, urbanization, agriculture and industry bave all markedly increased in recent decades and as the lower basin's levee protection system has been made increasingly vulnerable by river siltation. The total net discounted benefits of flood control and ice flood control are conservatively estimated to amount to about Y 3.83 billion (Us$ 733 million) over a period of 50 years, not counting the value of human lives protected. 3.2 Silt Reduction. The net effect of the project will be to stabilize the downstream river bed for at least 20 years and after 20 years, the dam will be operated to more effectively flush silt to the sea. This will defer the cost of raising the dikes and the economic benefit has been estimated at Y 1.06 billion (US$ 203 million). 3.3 Irrigation. Urban and Industrial Water Sunplies. The total area which may be supplied by irrigationwater is over 33 million mu (2.2 million ha), a substantialincrease over the 5-10 million mu which can presently be irrigatedwith supplies availablefrom the Yellow River. In addition, it is expected that the downstream urban and industrial demand of 4 billion m3/year by the year 2000 will be fully satisfied by the reservoir. The net discounted benefits are Y 3.92 billion (US$ 750 million). 3.4 Surface and Groundwater Balance. The improved surface water supply will permit reductions in groundwater withdrawals to be progressively applied, hence reducing current over-exploitation. This benefit is not quantified. -4- 3.5 ElectricityGeneration. The total installedcapacity of the hydroelectricplant is 1.800 KW with an average annual energy output of 5.4 billion kWh. This power will enhance economic developmentin the region. It will also significantly reduce greenhouse gas emissions. The net discounted benefits are Y 3.7 billion (US$ 710 uillion). 3.6 The total discounted economic benefits amount to Y 12.52 billion (USS 2.4 billion). The total discounted cost is Y 8.67 billion (US$ 1.66 billion) includingthe cost of constructionof the dam, resettlementand re-establishmentof livelihoodsof 181,000 people, upgradinghost communities of about 86,000 people, environmentalmanagement activities and operations and maintenancecosts for the project. The economic rate of return is 17%. 4. PROJECT ALTERNATIE 4.1 The main alternatives which have been considered in the past, and the reasons for their rejection are : (a) Raising the dikes to control a 1,000-year flood - this option is very costly and would involve considerable uncertainty due to structuralweaknesses of the dikes.