Enhancing hydropower resilience through dynamic rule curve modifications under climate change in the Sunkoshi multipurpose scheme, Nepal.

Amid Nepal's expanding hydropower sector, the Sunkoshi Multipurpose Scheme stands as a pivotal inter-basin transfer project. As the country seeks to maximize its abundant water resources, strengthening hydropower resilience against the inevitable impacts of climate change is imperative for ensuring long-term energy sustainability. This study conducts a comprehensive assessment of climate change impacts on the Sunkoshi River Basin and proposes an adaptive management strategy through dynamic rule curve modifications, optimizing reservoir operations in response to projected shifts in water availability across different time horizons of the 21st century. Seven bias-corrected General Circulation Models (GCMs) (ACCESS-CM2, BCC-CSM2-MR, CanESM5, EC-Earth3, MPI-ESM1-2-HR, MPI-ESM1-2-LR, and NorESM2-MM) were adopted for the projection of climate variables under Shared Socio-Economic Pathways (SSP)245 and SSP585 scenarios which were further utilized for the projection of future discharge in the Soil and Water Assessment Tool (SWAT). The anticipated inflow data served as input to the Hydraulic Engineering Center- Reservoir System Simulation (HEC-ResSim) software to simulate the reservoir operation and propose modified rule curves for Sunkoshi No.1, Sunkoshi No.2, Sunkoshi No.3, and Dudhkoshi hydropower projects for the time frame of 2030s, 2060s, and 2080s. Six different rule curves were proposed and average yearly energy generations were maximized ranging from 25.5%, 61.07%, 71.26%, and 10.50% for Sunkoshi No.3, Sunkoshi No.2, Sunkoshi No.1, and Dudhkoshi power plants respectively. These results could be helpful for long-term planning, urging policymakers to integrate dynamic rule curve modifications in the broader context of sustainable energy production and climate change adaptation.