Managing Hydropower Under Climate Change in the Mekong Tributaries

Abstract

The Mekong Basin is threatened by accelerated hydropower development and extreme events from climate change. The transboundary Srepok, Sesan, and Sekong (3S) basins contribute the largest discharge of Mekong River’s tributaries, providing critical ecosystem services to the Tonle Sap and the Mekong delta downstream, including sediments, biodiversity, and fish production. This study aims to assess the potential impact of climate change and hydropower development scenarios on flow patterns and hydropower production in the 3S through multi-general circulation models (GCMs), hydrological simulations, and reservoir operation models. Full hydropower development coupled with energy-focused operations will increase dry season flows by 96 % and reduce wet season flows by 25 % at the basin outlet as compared to historical baseline conditions. Climate change is likely to decrease dry season flows by 6–24 %, but projections of wet season and annual flows using different climate change scenarios and GCMs are relatively uncertain. Energy production in the 3S is not likely to be affected substantially by climate-driven changes in flows; only minor changes resulting from either A2 and B2 climate change scenarios and different GCMs. Predicted climate change, however, will result in significant changes in the magnitude and frequency of extreme flood events, which will undoubtedly impact on future dam design and operation rules. Coordination of hydropower operations within the 3S basin will be critical to maximise development benefits within the basin and reduce negative environmental impacts at the local, national, and transboundary levels.