Balancing competing interests in the Mekong River Basin via the operation of cascade hydropower reservoirs in China: Insights from system modeling

Abstract

As one of the most important international rivers in Asia, the Mekong River is famous for its abundant water and hydropower resources, fascinating biodiversity, and geopolitical importance. However, the rapid hydropower development in the Mekong River Basin has induced ecological risks and triggered water conflicts among six riparian nations. Balancing the competing interests of water, energy and ecosystems in the Mekong River Basin is a great challenge for riparian nations and is of global concern. This study quantitatively investigates what role the operation of the cascade reservoirs in China may play in mitigating existing conflicts and achieving cobenefits in the entire Mekong River Basin. An integrated modeling approach is adopted, and simulation-optimization analyses are performed to explore the tradeoff and/or synergy effects among the competing interests under varying reservoir operation strategies. The study reveals the disparate interactions among water, energy and ecosystem sectors and identifies the transboundary cobenefits of hydropower production and water supply. The major study findings are as follows. First, hydropower development in the upper Mekong River (also known as the Lancang River) can be beneficial for downstream agricultural water supply in certain circumstances if the cascade reservoirs in China are operated wisely. Second, the natural flow index adequately reflects ecological concerns in general, but additional objectives need to be included in the optimization if specific interests (e.g., phosphorous export from the Lancang River) are prioritized. Third, the tradeoffs between the agricultural water supply and ecosystem conservation, the two critical concerns of downstream countries, are intrinsic in the lower Mekong River Basin and are not induced by hydropower production in China. Fourth, the agricultural water supply in the downstream countries calls for a larger shift in the flow regime than hydropower production in China. Overall, the results of this study provide new insights into holistic management and effective transboundary cooperation in the Mekong River Basin, as well as in other international river basins with similar water-energy-ecosystem nexuses.