Streamflow modeling and contribution of snow and glacier melt runoff in glacierized Upper Indus Basin

The Upper Indus Basin has a large concentration of glaciers and mainly fed by snow and glacier melt. These melt runoffs are the primary driver of discharge and significantly contribute to Indus flows. Therefore, the present study was undertaken in the Upper Indus Basin (UIB) up to the Besham Quila site. This study focuses on quantifying runoff's contribution from different sources, including snow and glacier melt, and evaluates model performance in the glacierized Himalayan basin. The model was calibrated (1981-2000) and validated (2001-2007) daily and monthly using 27 years of measured discharge data at the Besham Quila station. A statistical indicator shows a "good" relationship between simulated and observed discharge on a daily and "very good" on a monthly timestamp. In this study, the annual contribution from snow/ice melt in the basin was quantified and found to be 51% of the total runoff. Apart from this, around 30% of water comes from direct runoff generated through liquid precipitation and 3.8% from groundwater. The remaining (similar to 15%) is contributed by interflows sourced from the rainfall and snow/ice melt. The basin receives 61% contribution from snow and glacier melt during monsoon (July-Sept) and 38% during summer (April-June) seasons, while negligible in other seasons. A decreasing trend is observed in modelled total runoff and melt runoff of about 1.11 x 10(9) m(3) a(-1) and 0.73 x 10(9) m(3) a(-1), respectively.