Assessing Cumulative Impacts of the Proposed Lower Mekong Basin Hydropower Cascade on the Mekong River Floodplains and Delta – Overview of Integrated Modeling Methods and Results

Abstract Approach, methods, and results from a comprehensive integrated water resources modeling framework for the Lower Mekong Basin (LMB) are presented in this paper. The modeling suite was specifically tailored to the known conditions and data availability at key locations within the LMB and more particularly within the floodplains of Cambodia and the Mekong River Delta of Vietnam. Model simulation output was used to project cumulative changes to hydraulic, sediment, and water quality parameters likely to occur in this relatively unique system under multiple scenarios of hydropower development in the LMB. While substantial changes in river flow regimes are predicted as a result of hydropeaking operations especially when combined with dry-season drawdowns to maximize power production, the multiple-scenario analysis indicated that overall, the largest changes are expected to be in loss of sediment and nutrient transport and reduction of water quality due to increased salinity intrusion into areas of the Mekong Delta.