Anticipated geomorphic impacts from Mekong basin dam construction

The Mekong River is undergoing rapid dam construction. Seven mainstem dams are completed or under construction in China and 133 completed or proposed for the Lower Mekong River basin. We combined geomorphic assessments of the Mekong channel and delta with models of sediment trapping by reservoirs to forecast geomorphic change. We expect the biggest changes to occur along alluvial reaches, though stripping of thin sediment deposits in bedrock reaches may also have significant consequences for benthic invertebrates, fishes, and other aquatic organisms dependent on the presence of alluvium in the channel. If all dams are built as proposed, the resulting 96% reduction in sediment supply would have profound consequences on productivity of the river and persistence of the delta landform itself. Strategies to pass sediment past dams should be implemented to reduce the magnitude of sediment starvation and resulting impacts.