Analysing hydrological balance of Pindar-Nandakini River Basin, Kumaon Himalaya using SWAT model

Water availability from the central Himalayan River Basins is threatened by warming-mediated glacier melt and declining precipitation. This study employed the Soil and Water Assessment Tool (SWAT) model to analyze the water balance of the Pindar-Nandakini River Basin (PRB). The model was calibrated and validated using high-resolution data, achieving strong performance (R²: 0.85, NSE: 0.71). Runoff and evapotranspiration (ET) account for approximately 29.7% and 28.9% respectively. Lateral soil flow is a major contributor (23.7% of precipitation), significantly influencing streamflow and groundwater levels. Snowmelt contributes around 10.3%, while deep groundwater flow is minimal. The model considerably simulated seasonal runoff patterns, particularly peak flows during the monsoon. Sediment loading, at 563.1 t ha-1 annually, is a significant concern. The study also underscores the critical role of ET and runoff in the hydrological processes of the basins, revealing potential challenges during high-flow events and climate-driven forest greening trends. These findings emphasize the importance of the SWAT model in understanding the complex hydrological processes within the Himalayan glacier basins, highlighting the basin's vulnerability to climate change impacts, particularly glacier retreat.