Dams in the Mekong River Basin: Options for Improved Sediment and Fish Passage

Abstract:

The Mekong River and its tributaries comprise one of the most productive fish habitats in the world today. The economic value of the Mekong fishery in Lao PDR, Cambodia and Vietnam is among the highest in the world, providing income and food security to tens of millions of people. However, the construction of multiple dams in the basin will reduce sediment discharge, which will adversely impact nutrient transport and habitat quality and availability, and disrupt fish migration routes. Thus, of considerable interest is the identification of alternatives to the location, design and operation of planned hydropower dams that could improve sediment passage, enable migratory fish passage, and sustain fish production for local use. This paper describes the results of simulation studies designed to identify and evaluate such alternatives, as well as their potential impact on hydropower production. Dam sites in Cambodia and Lao PDR on tributaries and on the mainstream Mekong River will be discussed. Evaluations of sediment management techniques such as flushing, sluicing and bypassing will be discussed. This study is intended to inform decision makers in Cambodia, Lao PDR and Vietnam about potential alternatives to current plans as they prepare decisions regarding the development of over 100 hydropower dams throughout the basin.