Assessing the impact of upstream reservoirs on streamflow in the Mekong River Basin

ABSTRACT The Mekong River Basin (MRB) is a crucial transboundary region that provides essential ecosystem services, including water for consumption, agriculture, and fisheries. However, hydropower development poses a major challenge, as dams on the river and its tributaries alter its natural flow, impacting both ecological and social systems. This study assesses the effects of reservoirs by integrating the CaMa-Flood-Dam reservoir model with the Watershed Environmental Hydrology (WEHY) Model. Fifteen major hydropower reservoirs in China, Thailand, and Laos were selected based on their location, purpose, and storage capacity impact on downstream flow. The models were carefully calibrated and validated before analyzing the effects of dams. Findings reveal that reservoir impact is directly linked to storage capacity, with China's large reservoirs exerting the most significant influence on downstream flow. Laos follows, while Thailand and Vietnam, with smaller reservoirs, have minimal effects. Additionally, the study highlights the benefits of integrating a physically based hydrology model with dam operations, enabling a more accurate reconstruction and assessment of reservoir influence. The proposed approach can simultaneously simulate rainfall, streamflow, and dam operations, offering reliable forecasts and projections of flow conditions across the MRB. This method provides valuable insights for sustainable water management in the region.