Mekong River flow and hydrological extremes: climate change, dam, and reservoir impacts

Climate change and man-made structures threaten water safety and sustainability in the Mekong River basin, a significant transboundary river basin in Southeast Asia. However, the current understanding of hydrological changes under the combined impacts of these drivers still needs to be improved to support sustainability across the region. This study investigates the effects of 124 existing and near-future dams and reservoirs coupled with implications from climate change (using climate projections from the Coupled Model Intercomparison Project Phase 6; CMIP6) for the Mekong basin. We found that the future annual and seasonal flow regimes are highly susceptible to the considered drivers, while near-future dams and reservoirs exhibit limited flood and drought prevention capacity. Furthermore, the cumulative impacts of all drivers cause significant flow reductions during the early wet season, posing challenges for water management and crop production in the downstream Mekong Delta. These findings highlight the need for careful consideration in developing strategic plans and executing anthropogenic activities over the Mekong.