Improved trade-offs of hydropower and sand connectivity by strategic dam planning in the Mekong

Dams in the Mekong Basin are mostly planned project-by-project and without strategic analysis of their cumulative impacts on river processes such as sediment connectivity. We analyse missed and future opportunities for reducing hydropower impacts on sediment connectivity through strategic planning of dams in the Se Kong, Se San and Sre Pok (‘3S’) tributaries of the lower Mekong, which are critically important as a source of sand for the Mekong Delta. With strategic planning, 68% of the hydropower potential of the 3S Basin could have been developed while trapping 21% of the basin’s sand load. The current dam portfolio resulting from project-by-project planning uses 54% of the hydropower potential while trapping 91% of the sand load. Results from the 3S demonstrate that strategic network-scale planning is crucial for developing lower-impact hydropower, a relevant finding given the at least 3,700 major dams that are proposed worldwide.