Electricity of Vietnam Power Engineering Consulting Company No
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www.sweco.no Electricity of Vietnam Power Engineering Consulting Company no. 1 FINAL REPORT Environmental Impact Assessment on the Cambodian part of the Se San River due to Hydropower Development in Vietnam December 2006 SWECO Grøner in association with Norwegian Institute for Water Research, ENVIRO-DEV, and ENS Consult Environmental Impact Assessment on the Cambodian part of the Se San River December 2006 due to hydropower development in Vietnam Final Report SWECO Grøner in association with Final Report 2/187 NIVA, ENVIRO-DEV, and ENS Consult Environmental Impact Assessment on the Cambodian part of the Se San River December 2006 due to hydropower development in Vietnam Final Report ACKNOWLEDGEMENTS ...................................................................................................................6 EXECUTIVE SUMMARY ....................................................................................................................7 1. INTRODUCTION AND METHODOLOGY.............................................................................18 1.1 .....BACKGROUND .........................................................................................................................18 1.2 .....OBJECTIVES OF THE PROJECT ..................................................................................................19 1.3 .....BASELINE DESCRIPTION ..........................................................................................................20 1.4 .....DATA, METHODS AND LIMITATIONS .......................................................................................20 1.5 .....STUDY AREA...........................................................................................................................21 1.5.1 Landscape and Ecology ..................................................................................................22 1.5.2 Aquatic Ecology .............................................................................................................22 1.5.3 Administrative Areas and Population.............................................................................23 1.5.4 Ethnicity .........................................................................................................................28 1.5.5 Socio-economic Setting..................................................................................................28 1.5.6 Living and Health Standards ..........................................................................................30 1.6 .....STUDY METHODS ....................................................................................................................31 1.6.1 Study Process..................................................................................................................31 1.6.2 Study Topics...................................................................................................................32 1.6.3 Methodology for an Integrated Field Study....................................................................33 1.6.4 Integration of Data into Impact Assessment...................................................................36 2. HYDROPOWER PROJECTS ON THE VIETNAMESE PART OF SE SAN RIVER ...........38 2.1 .....OVERALL ASPECTS OF HYDROPOWER DEVELOPMENT IN SE SAN RIVER.................................38 2.2 .....HYDROPOWER PROJECTS IN OPERATION .................................................................................38 2.2.1 Ialy Hydropower Project.................................................................................................38 2.3 .....HYDROPOWER PROJECTS UNDER CONSTRUCTION ...................................................................41 2.3.1 Pleikrong Hydropower Project .......................................................................................41 2.3.2 Se San 3 Hydropower Project.........................................................................................42 2.3.3 Se San 3A Hydropower Project......................................................................................42 2.3.4 Se San 4 Hydropower Project.........................................................................................43 2.4 .....COMMITTED HYDROPOWER PROJECTS ....................................................................................44 2.5 .....HYDROPOWER PROJECTS UNDER PLANNING ...........................................................................44 2.5.1 Upper Kontum Hydropower Project...............................................................................44 2.6 .....SE SAN 4A RE-REGULATION RESERVOIR ................................................................................46 3. HYDROLOGY AND FLOW CHARACTERISTICS OF OPERATION.................................47 3.1 .....THE SE SAN RIVER SYSTEM ....................................................................................................47 3.2 .....CLIMATIC CONDITIONS ...........................................................................................................48 3.3 .....HYDROLOGICAL AND METEOROLOGICAL DATA .....................................................................48 3.3.1 Meteorological Data .......................................................................................................48 3.3.2 Hydrological Data...........................................................................................................48 3.4 .....FLOOD FLOW EVENTS .............................................................................................................49 3.5 .....HYDRODYNAMIC MODELING ..................................................................................................49 3.5.1 Introduction ....................................................................................................................49 3.5.2 Historical Flow Condition ..............................................................................................50 3.5.3 “Natural Flow” Conditions.............................................................................................51 3.5.4 Some of the Main Simulation Results ............................................................................55 3.5.5 River Modeling – Spillway Operation Rules for the Dams ............................................57 3.5.6 Variation in spill discharge and time period...................................................................59 4. IMPACTS FROM THE THE IALY HYDROPOWER PROJECT REPORTED BY OTHER STUDIES...............................................................................................................................................61 4.1 .....REPORTS EVALUATED .............................................................................................................61 4.2 .....CHANGE IN RAINY SEASON FLOODING....................................................................................61 4.2.1 Extreme Flood in 1996 ...................................................................................................62 4.3 .....RAPIDLY RISING WATER LEVEL..............................................................................................62 4.4 .....DRY SEASON WATER LEVEL FLUCTUATIONS..........................................................................63 4.5 .....WATER QUALITY PROBLEMS ..................................................................................................63 4.6 .....IMPACTS ON RIVERINE VEGETATION .......................................................................................64 4.7 .....IMPACTS ON FISH, FISH HABITAT, AND FISHERIES ..................................................................65 4.8 .....IMPACTS ON HUMAN LIVELIHOOD SYSTEMS ...........................................................................65 5. DESCRIPTION OF THE PRESENT SITUATION...................................................................67 5.1 .....WATER QUALITY ....................................................................................................................67 SWECO Grøner in association with Final Report 3/187 NIVA, ENVIRO-DEV, and ENS Consult Environmental Impact Assessment on the Cambodian part of the Se San River December 2006 due to hydropower development in Vietnam Final Report 5.1.1 Sampling sites and parameters........................................................................................67 5.1.2 Temperature and oxygen stratification in the Ialy Reservoir..........................................69 5.1.3 General water quality and nutrients................................................................................70 5.1.4 Water quality data from 2001 provided by MOWRAM.................................................72 5.1.5 Water Quality Results from Monitoring in 2004/2005 provided by MOWRAM...........73 5.1.6 Water quality analyses from 2004 and 2006 provided by PECC1..................................76 5.1.7 Algal analysis .................................................................................................................78 5.1.8 Analysis of algal toxins ..................................................................................................81 5.1.9 Heavy metals ..................................................................................................................82 5.1.10 Pesticides ........................................................................................................................82 5.1.11 Conclusions on the present water quality