China - Xiaolangdi Multipurpose Dam Project : environmental impact assessment

Environmental Assessment/Analysis Reports _______ Report E0030 China - Xiaolang di Multipurpose/ Ressetlement Proj'ect EA Category A Xiaolangdi Multipurpose Dam Project Februay 1993 This report has been prepared by the Borrower or its Consultant  XIAOLANCDI MULTIPURPOSE PROJECT ENVIRONMENTAL ASSESSMENT SUMMARY (SUMMARY OF EIA EXECUTIVE SUMMARY) 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 information can be found. 2. PROJECT OBJECTIVES AND DESCRIPTION Objectives and Background 2.1 The primary objectives of 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-1,000 years after completion. However, there are at present three million people living within the dykes and downstream flood detention basins 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 discharge capacity 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