VOLUME II PAPER VI WATER USE IN THE LOWER MEKONG BASIN FINAL REPORT MARCH 2004 WUP-JICA TEAM Vol. II: Supporting Report, Paper VI: Water Use in the Lower Mekong Basin WUP-JICA, March 2004 TABLE OF CONTENTS SUMMARY ......................................................................................................... VI-1 1. INTRODUCTION ................................................................................. VI-8 2. EXISTING WATER RESOURCE FACILITIES IN THE MEKONG RIVER BASIN .................................................................... VI-9 2.1 Existing Large Reservoirs ............................................................. VI-9 2.2 Overview of Water Resources Developments in the Mekong Countries ......................................................................... VI-10 2.3 Existing Hydropower Plants .......................................................... VI-18 2.4 Surface Water Extraction for Domestic Water Supply .................. VI-24 2.5 Operation Records of Existing Flow-Regulating Facilities ........... VI-26 2.6 Seasonal Regulation Rate of Mekong Flow by Major Reservoirs . VI-26 3. AVAILABLE INFORMATION ON IRRIGATION AREA IN LOWER MEKONG BASIN ................................................................. VI-28 3.1 Overview of Land Use in the Lower Mekong Basin ..................... VI-28 3.2 Historic Overview of Irrigation Areas ........................................... VI-28 3.2.1 Indicative Basin Plan in 1970 ........................................... VI-30 3.2.2 Revised Indicative Plan in 1987 ....................................... VI-31 3.2.3 Other Existing Reports ..................................................... VI-33 3.3 Land Resources Inventory for Agricultural Development Project by MRC................................................................................. VI-44 3.4 Surface Water Extraction by Pumping-up Irrigation ..................... VI-48 4. CURRENT WATER USE IN THE LOWER MEKONG BASIN ..... VI-52 4.1 General .......................................................................................... VI-52 4.2 Estimated Irrigation Diversion Requirements from Past Studies .. VI-52 4.3 Estimated Return Flows from Past Studies ................................... VI-53 4.4 Current Water Use in Thailand ...................................................... VI-54 4.5 Current Water Use in Lao PDR ..................................................... VI-60 4.6 Current Water Use in Cambodia ................................................... VI-61 4.7 Current Water Use in Vietnam ...................................................... VI-62 5. IDENTIFICATION OF LOW FLOW INCREASE DUE TO NAM NGUM HYDROPOWER DEVELOPMENT PROJECT IN NAM NGUM RIVER ....................................................................... VI-64 5.1 Nam Ngum Hydropower Development Project ............................ VI-64 5.2 Operation Records of Nam Ngum Hydropower System ............... VI-64 V-i Vol. II: Supporting Report, Paper VI: Water Use in the Lower Mekong Basin WUP-JICA, March 2004 5.3 Operation Pattern of Nam Ngum Hydropower Station .................. VI-66 5.4 Low Flow Increase in the Nam Ngum River ................................. VI-69 6. IDENTIFICATION OF LOW FLOW CHANGE OF NAM MUN-CHI RIVER DUE TO INTENSIVE WATER RESOURCES DEVELOPMENT .................................................................................. VI-75 6.1 Nam Mun-Chi River Basin in North-eastern Thailand .................. VI-75 6.2 Large Scale Water Resources Development Projects in North-Eastern Thailand .................................................................. VI-76 6.3 Changes in Low Flow Regime of the Nam Mun-Chi River .......... VI-78 6.4 Low Flow Check at the Confluence with Mekong Mainstream .... VI-84 6.5 Effect of Existing Reservoirs on River Runoff .............................. VI-86 6.6 Low Flow Increases due to Existing Large Reservoirs .................. VI-86 7. ASSESSMENT OF LOW FLOW INCREASE DUE TO LATERAL INFLOWS ALONG THE MEKONG MAINSTREAM ..................... VI-93 7.1 Hydrological Network Stations ...................................................... VI-93 7.2 Selected Hydrological Network Stations for Assessment .............. VI-94 7.3 Basic Conditions for Assessment ................................................... VI-96 7.4 Results of Assessment ................................................................... VI-97 7.4.1 Chiang Saen-Luang Prabang ............................................. VI-98 7.4.2 Luang Prabang-Chiang Khan ............................................ VI-99 7.4.3 Chiang Khan-Vientiane and Vientiane-Nong Khai .......... VI-100 7.4.4 Nong Khai-Nakhon Phanom ............................................. VI-107 7.4.5 Nakhon Phanom-Mukdahan ............................................. VI-108 7.4.6 Mukdahan-Kong Chiam .................................................... VI-109 7.4.7 Kong Chiam-Pakse ........................................................... VI-110 7.4.8 Pakse-Stung Treng ............................................................ VI-111 7.4.9 Stung Treng-Kratie ........................................................... VI-112 7.4.10 Kratie-Kompong Cham ..................................................... VI-113 7.4.11 Kompong Cham-Chroui Changvar ................................... VI-114 REFERENCES .................................................................................................... VI-115 VI - ii Vol. II: Supporting Report, Paper VI: Water Use in the Lower Mekong Basin WUP-JICA, March 2004 LIST OF TABLES Table 2.1 Salient Features of Existing Large Reservoirs ............................ VI-9 Table 2.2 Comparison of Total Storage Volume by Riparian Country ....... VI-9 Table 2.3 Hydropower Development in Lancang River in China ............... VI-12 Table 2.4 Percent Increase to Mean Monthly Flow on the Mekong Mainstream due to Cascade Power Development in China ........ VI-12 Table 2.5 Existing Hydropower Projects in Myanmar ................................ VI-13 Table 2.6 Power Generation and Supply Balance in Lao PDR ................... VI-14 Table 2.7 Present Status of IPP Schemes in Lao PDR as of End 2001 ....... VI-14 Table 2.8 Salient Feature of Existing Hydropower Plants .......................... VI-18 Table 2.9 Detailed Features of Existing Run-of-river Plants in China ....... VI-21 Table 2.10 Comparison of Estimated Maximum Plant Discharges and Firm Discharges of Existing Run-of-river Plants in China ....................................................................................... VI-22 Table 2.11 Monthly Operation Record at Houay Ho Hydropower Stations ... VI-119 Table 2.12 Major River Intakes for Domestic Water Supply in Lao PDR (1999) .......................................................................... VI-24 Table 2.13 Major River Intakes for Domestic Water Supply in Cambodia (2002) .................................................................... VI-25 Table 2.13 Water Abstractions for Domestic Water Supply in 1990 ............ VI-26 Table 2.15 Projected Domestic Water Demand in 2000 and 2015 for Entire Mekong Delta ............................................................. VI-26 Table 3.1 Drainage Area of Mekong River Basin ....................................... VI-28 Table 3.2 Land Use in the Lower Mekong Basin in 1997 .......................... VI-28 Table 3.3 Contributions Agriculture and Forestry to GDP of Each Riparian Country ................................................................ VI-30 Table 3.4 Contributions of Agriculture and Forestry to LMB Country Exports .......................................................................... VI-30 Table 3.5 Cultivated Areas in Lower Mekong Basin (1965) ...................... VI-31 Table 3.6 Irrigated Areas in Lower Mekong Basin (1970) ......................... VI-31 Table 3.7 Irrigated Areas in Lower Mekong Basin (1987) ......................... VI-32 Table 3.8 National Irrigation Projects in Lower Mekong Basin (1987) ......... VI-33 Table 3.9 Historic Irrigated Area (1990-2000) in Lao PDR ....................... VI-33 Table 3.10 Existing Irrigation Schemes in Lao PDR .................................... VI-35 Table 3.11 Existing Irrigated Area in Lao PDR (1995) ................................ VI-35 Table 3.12 Existing Irrigated Area in Lao PDR (2000/2001) ....................... VI-36 Table 3.13 Existing Irrigation Area of Mekong Basin in Lao PDR (2000) ...... VI-36 Table 3.14 Existing Irrigation Area of Mekong Basin in Thailand .............. VI-37 Table 3.15 Summary of Existing Irrigation Schemes in North-eastern Thailand (1/2) & (2/2) .......................................... VI-38 Table 3.16 Area of Rice Production by Year in Cambodia .......................... VI-40 Table 3.17 Inventory of Existing Irrigation Systems in Cambodia (1992/93).. VI-41 VI - iii Vol. II: Supporting Report, Paper VI: Water Use in the Lower Mekong Basin WUP-JICA, March 2004 Table 3.18 Cropping Patterns and Yields in Cambodia ................................ VI-41 Table 3.19 Existing Irrigated Areas in Cambodia (1990) ............................. VI-42 Table 3.20 Existing Irrigated Rice Areas in Mekong Delta in Vietnam ....... VI-43 Table 3.21 Cropping Patterns of Mekong Delta in Vietnam ......................... VI-44 Table 3.22 Summary of Irrigation Projects under LRIAD in Lower Mekong Basin ............................................................................. VI-45 Table 3.23 Summary of Status of Irrigation Database