Impact of land use and land cover change in river flow and hydro-energy generation: The case of Bagmati basin in central Nepal

The hydrological dynamics of the Bagmati River downstream from Kathmandu have transformed due to rapid urbanization, impacting regional water projects. Declining open land and groundwater levels have reduced winter base flow and increased summer peak discharge, challenging sustainable energy generation. This study quantifies Land Use and Land Cover (LULC) impact on downstream hydropower. Using LULC data and a calibrated hydrological model in SWAT, it introduces change scenarios, analyzing their influence on river runoff and energy generation. Results reveal varied runoff curve numbers and seasonal discharge due to LULC shifts. Annual mean flow sees a 1.3% increase, while lean flow decreases by 3.45%. Consequently, dry, wet, and total energy generation drops annually by 0.68%, 0.31%, and 0.38%, respectively. The Flow Duration Curve (FDC) notably shifts upwards at its top and downwards at the bottom compared to the base simulation, defining the most sustainable installed capacity. Additionally, the study presents a regression equation based on LULC changes for simplified analysis. It underscores the crucial role of LULC modifications in river runoff, profoundly impacting energy generation and water resource projects' sustainability. Neglecting these changes could severely affect project success.