The mitigation on future flood and hydrological drought under reservoir regulation: A case study in Nu-Salween river basin

The hydrological processes of the Nu-Salween River (NSR) Basin are increasingly challenged by climate change in the 21st century. Effective water resources management, particularly reservoir regulation, plays a key role in flood control and drought mitigation. This study employs the Geomorphology-Based Hydrological Model of the NSR Basin (GBHM-NSR), incorporating a reservoir regulation scheme for simulating the impact of a hypothesized reservoir, to: 1) assess the trends of flooding and drought under future climate change scenarios across the NSR Basin, and 2) evaluate the possible impact of reservoir regulation on the frequency and magnitude of future flood and hydrological drought events. The results indicate an anticipated increase in both the frequency and magnitude of floods, alongside a decrease in drought risk under climate change. The midstream area is identified as particularly vulnerable to hydrological anomalies. Reservoir regulation serves to stabilize intra-annual streamflow, mitigating both flood and hydrological drought risks in the future under three SSP-RCP scenarios, with the most pronounced effects observed under the SSP2-RCP4.5 scenario, indicating the reservoir regulation scheme is of greater effectiveness under the future scenario with continuing pathways as present condition. However, in the future scenario with higher severity of climate change and hydrological extremities (SSP5-RCP8.5), more targeted and strengthened regulatory strategies will be necessary to achieve better water security for riparian communities and maintain hydrological stability, both of which are essential for sustaining ecosystem services, supporting socioeconomic development, and adapting to climate variability.