Modeling streamflow sensitivity to rainfall variability in the Budhigandaki River basin in Nepal

Abstract

Snow-fed River Basins in Nepal are vital water sources, which are increasingly vulnerable to climate changeinduced variability in rainfall. This study focuses on the Budhigandaki River Basin to analyze streamflow sensitivity to rainfall variability and assess its impact on drought conditions, providing insights for effective water management and adaptation strategies. The Hydrologic Engineering Center's Hydrologic Modeling System (HEC-HMS) was used to simulate streamflow under rainfall scenarios varying up to ±15%. Drought conditions were categorized using specific percentile thresholds into four levels: extreme, severe, moderate, and mild. Results show that a modest annual rainfall variation of 5% can significantly alter drought conditions, highlighting the hydrological sensitivity of the basin. Increased precipitation improved moderate drought conditions, demonstrating the resilience of the basin, while decreased rainfall exacerbates drought severity. Transitions of drought categories were observed with varying rainfall amounts, suggesting that even minor changes can lead to significant shifts in drought severity. While this study uses specific percentage increments in rainfall, simplifying the complexity of annual rainfall variability, these findings highlight the critical need for adaptive water resource management strategies in response to varying rainfall and climate change.