The mitigation of reservoirs on extreme hydrological events in Lancang-Mekong River Basin under changing climate

The Lancang-Mekong River (LMR) Basin is highly vulnerable to extreme hydrological events, including floods, droughts, and their combinations, such as Drought-Flood Abrupt Alternation (DFAA). The impacts of climate change on these extremes and the efficacy of potential adaptation measures remain poorly understood. This study investigates these dynamics using five Global Climate Models (GCMs) from the Coupled Model Intercomparison Project Phase 6 (CMIP6). It employs the Standardized Runoff Index (SRI) and the Regional Drought-Flood Abruptness Index (R-DFAI) alongside the Tsinghua Representative Elementary Watershed (THREW) model, integrated with a reservoir module. Results reveal that the LMR Basin, particularly its upstream regions, is projected to face heightened susceptibility to drought during the near future (2021–2060) and increased flood risks in the far future (2061–2100). Under SSP126 and SSP245 scenarios, DFAA risks escalate, especially downstream and during the wet season, whereas under SSP585, these risks decline. Reservoirs as a promising adaptation strategy can significantly mitigate extreme hydrological events and DFAA, particularly in regions with higher total reservoir storage. However, their efficacy in controlling downstream floods diminishes in the far future. Reservoir operations reduce DFAA’s intensity, limit multi-peak occurrences, shorten its monthly span, and alleviate risks during critical agricultural periods. These insights offer valuable guidance for effective water resource cooperative management across LMR Basin countries.