Water, Watt, and Warming: Hydropower Futures in the Eastern Nepal Himalayas under Climate Change

Conceptual infographic illustrating the cascade of climate-change impacts on mountain hydrology and hydropower systems. The figure begins with climate warming under SSP2-4.5 and SSP5-8.5 scenarios, depicted by warming mountain landscapes and glacier retreat. Increased temperatures (up to +3°C) drive snowmelt and hydrological regime shifts, altering seasonal river flows. Winter discharge increases substantially (up to ~105%), while transition seasons and monsoon-period flows are redistributed. These hydrological changes create a seasonal mismatch in hydropower production, with winter electricity generation surging (up to ~230%), whereas annual hydropower gains remain relatively modest (~10–16%). The lower section highlights challenges for run-of-river hydropower schemes, which are vulnerable to mismatches between water availability and energy demand. The diagram concludes by emphasizing the need for climate-resilient hydropower design, including flexible infrastructure, storage and regulation capacity, and adaptive operational strategies to manage future hydrological variability. Climate change is redefining water–energy interactions in high-mountain regions, yet its implications for hydropower reliability and design remain poorly understood. This paper quantifies future hydroclimatic and energy responses in a snow-fed Himalayan basin using Soil and Water Assessment Tool (SWAT+) within the Coupled Model Intercomparison Project, Phase 6 (CMIP6) framework, which incorporates bias-corrected projections and elevation-dependent processes to capture high-altitude dynamics. A multi-model ensemble under shared socioeconomic pathways (SSP): SSP2-4.5 and SSP5-8.5 reveals robust warming (up to ∼3 °C) and a fundamental alteration of the hydrological regime. Streamflow intensifies but becomes increasingly seasonal, with winter discharge rising by up to ∼105% while transitional seasons weaken. These shifts translate into disproportionate hydropower gains, with winter generation increasing by up to ∼230%, whereas annual gains remain modest (∼10–16%). The dominant signal is not uniform resource expansion but growing temporal imbalance. This emerging seasonality challenges the adequacy of conventional run-of-river systems, which are optimized for historical flow conditions. Without adaptive strategies, such as flexible design, discharge, and improved seasonal regulation, future hydropower performance may be constrained despite increasing water availability. These findings highlight a critical mismatch between evolving hydroclimates and infrastructure design, providing a robust basis for climate-resilient hydropower planning in mountain regions.