The Sekong River in Viet Nam, Lao PDR The Sekong River in Viet Nam, Lao and Cambodia PDR and Cambodia An Information Sourcebook for Dialogue on River Flow Management An Information Sourcebook for Dialogue on River Flow Peter-John Meynell Management BRIDGE: Building River Dialogue and Governance The designation of geographical entities Published by: Cover photo: in this book, and the presentation of the IUCN Asia Regional Office IUCN material, do not imply the expression of any opinion whatsoever on the part of Copyright: Produced by: IUCN (International Union for ©2014 International Union for IUCN Asia Regional Office Conservation of Nature) or the Swiss Conservation of Nature and Natural Agency for Development and Resources Available from: Cooperation concerning the legal status IUCN (International Union for of any country, territory, or area, or of its Reproduction of this publication for Conservation of Nature) authorities, or concerning the educational or other non-commercial Asia Regional Office delimitation of its frontiers or purposes is authorized without prior 63 Sukhumvit Soi 39 boundaries. written permission from the copyright Sukhumvit Road holder provided the source is fully Wattana, Bangkok 10110 The views expressed in this publication acknowledged. Reproduction of this Thailand do not necessarily reflect those of IUCN publication for resale or other Tel: +662 662 4029 or the Swiss Agency for Development commercial purposes is prohibited http://www.iucn.org/about/union/secretar and Cooperation. without prior written permission of the iat/offices/asia/regional_activities/bridge copyright holder. _3s/ The BRIDGE project is funded by the Citation: Swiss Agency for Development and Meynell, P. (2014). The Sekong River Cooperation. in Viet Nam, Lao PDR: and Cambodia: An Information Sourcebook for Dialogue on River Flow Management. Bangkok, Thailand: IUCN. 139pp. 2 TheThe Sekong Sekong River River in in Viet Viet Nam, Nam, Lao Lao PDR andPDR Cambodia and Cambodia An Information Sourcebook for Dialogue on River Flow Management An Information Sourcebook for Dialogue on River Flow Management Peter-John Meynell Peter-John Meynell 3 Table of contents 1 Introduction ................................................................................................................................................... 6 1.1 Using this information source book .................................................................................................... 6 1.2 Methodologies used ............................................................................................................................. 6 1.2.1 GIS analysis ................................................................................................................................... 6 1.2.2 Databases ...................................................................................................................................... 7 1.2.3 Google Earth survey ..................................................................................................................... 7 1.2.4 Flow Health modelling .................................................................................................................. 8 2 The Sekong River in context ...................................................................................................................... 9 2.1 Mekong ................................................................................................................................................... 9 2.2 3S Rivers .............................................................................................................................................. 10 2.2.1 Ecological Diversity of 3S Rivers .............................................................................................. 14 2.2.2 Ecological Uniqueness ............................................................................................................... 15 3 Characteristics of the Sekong River ........................................................................................................ 16 3.1 Structure and stream order ................................................................................................................ 19 3.2 Elevation ............................................................................................................................................... 20 3.3 Slope ..................................................................................................................................................... 26 3.4 Geology ................................................................................................................................................ 29 3.5 Soils ...................................................................................................................................................... 34 3.6 Climate .................................................................................................................................................. 38 3.6.1 Rainfall .......................................................................................................................................... 38 3.6.2 Temperature ................................................................................................................................ 40 3.7 Ecological zones ................................................................................................................................. 41 3.8 Landuse and forest cover .................................................................................................................. 48 3.9 Protected Areas and Key Biodiversity Areas .................................................................................. 52 4 Hydrology .................................................................................................................................................... 54 4.1 Flows in the Sekong ........................................................................................................................... 54 4.2 Floods and drought ............................................................................................................................. 57 5 Key features of the river ............................................................................................................................ 62 5.1 Profile of the Sekong River ................................................................................................................ 62 5.2 Profile of the Se Kamman .................................................................................................................. 64 5.3 Sinuosity of the Sekong ..................................................................................................................... 65 5.4 Mapping the features of the Sekong ................................................................................................ 68 5.5 Rapids and deep pools ...................................................................................................................... 71 5.6 Suggested E-flow reference sites ..................................................................................................... 73 5.6.1 Lowland river ............................................................................................................................... 74 5.6.2 Transition zone reaches ............................................................................................................. 75 5.6.3 Middle reaches ............................................................................................................................ 76 5.6.4 Upland river .................................................................................................................................. 77 5.6.5 Upland plateau ............................................................................................................................ 78 5.6.6 Se Kamman ................................................................................................................................. 79 6 Biological information ................................................................................................................................ 81 6.1 Fishbiodiversity .................................................................................................................................... 81 6.1.1 Fish endemism in the 3S Rivers ............................................................................................... 81 6.1.2 Endangered species in the 3S Rivers ...................................................................................... 82 6.2 Fish migrations in the 3S Rivers ....................................................................................................... 82 6.3 Fish breeding and spawning sites .................................................................................................... 85 6.4 Fish conservation zones .................................................................................................................... 85 7 People and communities ........................................................................................................................... 87 7.1 Viet Nam ............................................................................................................................................... 87 7.2 Lao PDR ..............................................................................................................................................