The theoretical hydropower potential of the river basins in Nepal in a changing climate

While it is well-established that Nepal is one of the leading countries in hydropower potential, limited studies have explored how this potential will change in the future. Future climate projections suggest changes in discharge patterns, which will impact the hydropower potential. Hence, this study provides an estimate of current and future theoretical run-of-river (RoR) hydropower potential in the four major basins of Nepal: Mahakali, Karnali, Gandaki, and Koshi, for 48 combinations of future climate scenarios. The contribution of discharge components (baseflow, rainfall runoff, snowmelt, and glacier melt) to the hydropower potential are analysed separately at monthly timescales for the reference period (1979–2018), mid-century (2036–2065), and end-of-century (2071–2100). This study estimates the total theoretical RoR hydropower potential of the four Nepalese basins to be 1472 TWh yr ^−1 during the reference period. The highest potential lies in the Koshi basin with 722 TWh yr ^−1 and lowest in the Mahakali basin with 151 TWh yr ^−1 . Under the 48 climate scenarios, the monthly theoretical hydropower potential changes −5%–19% by the mid-century and −20%–31% by the end of the century on average across the four basins. We report that a change in precipitation is the key driver of changes in hydropower potential. Additionally, we find that the discharge originating from snow- and glacier melt contributes proportionally more to the hydropower potential than to the total discharge. Our findings indicate that the future theoretical hydropower potential could potentially accommodate the projected increasing electricity demand. It is however essential to systematically assess which part of the theoretical potential can be harnessed in a sustainable way.