Dynamics of snow and glacier cover in the Upper Karnali Basin, Nepal: an analysis of its relationship with climatic and topographic parameters

Abstract. Snow and glacier cover in the Upper Karnali Basin (UKB) are crucial freshwater reservoirs that support downstream ecosystems and human populations. This study uses remote sensing and GIS data from various sources, including MODIS-derived land surface temperature and ERA5 reanalysis climate datasets, to analyze snow cover dynamics from 2002 to 2024. The results show a significant decrease in snow-covered area (SCA), with an annual decline of approximately 3.99 km2. Seasonal variations indicate the most significant reductions during the monsoon period (July–September), when rising temperatures accelerate snowmelt. The analysis also identifies a strong negative correlation between snow cover and temperature (r=-0.59 to −0.77, p<0.05), with warming trends disproportionately affecting mid- to high-elevation zones (3000–5000 m a.s.l.). Glacier basins exhibit consistent retreat, with the mean glacier area decreasing from 119.05 ha in 2000 to 100.47 ha in 2023, highlighting the impact of climate change. Additionally, snowline analysis shows upward migration, with the 10th-percentile snowline rising at approximately 5.16 m yr−1, indicating progressive snow loss at lower elevations. Given the current warming trends (∼0.0643 °C yr−1 above 5000 m a.s.l.), the UKB could experience a decline in glacier area by 47 %–69 % and snow-covered area by 19 %–30 %. These findings highlight the vulnerability of the UKB's cryosphere to climate change, emphasizing the need for adaptive water resource management strategies to mitigate impacts on hydrology, agriculture, and regional water security.