Mitigating the Impact of Increased Drought-Flood Abrupt Alternation Events under Climate Change: The Role of Reservoirs in the Lancang-Mekong River Basin

Source abstract

Abstract. The Lancang-Mekong River (LMR) Basin is highly vulnerable to extreme hydrological events, including Drought-Flood Abrupt Alternation (DFAA). The impact of climate change on DFAA and the efficacy of potential mitigation measures such as reservoirs 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 Revised Short-cycle Drought-Flood Abrupt Alteration Index (R-DFAI), alongside the Tsinghua Representative Elementary Watershed (THREW) model integrated with the developed reservoir module. Results reveal that future DFAA trend varies widely in upstream and downstream, with significant increases respectively in FTD (flood to drought) upstream and DTF (drought to flood) downstream. FTD is more challenging though DTF is more probable to occur. Under SSP126 and SSP245 scenarios, DFAA risks escalate, especially during the wet season, whereas under SSP585, these risks decline. Reservoirs as a promising adaptation strategy can significantly mitigate year-round DTF and wet season's FTD, particularly in regions with higher total reservoir storage. Reservoir operations reduce DFAA's intensity, limit multiple peaks and shorten its monthly span. Hydrological forecasting and resilient storage enables to be viable options for climate change to help LMR Basin smooth out DFAA. These insights offer valuable guidance for effective water resource cooperative management across LMR Basin countries.