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, MODIS-derived land surface temperature, and ERA5 reanalysis climate datasets to analyze snow cover dynamics from 2002 to 2023/24. The results show a significant decrease in snow-covered area (SCA), with an annual decline of about 3.99 km². Seasonal variations indicate the most significant reductions during the monsoon period (July-September), where rising temperatures accelerate snowmelt. The analysis also establishes 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 masl). Glacier basins exhibit consistent retreat, with the mean glacier area declining from 119.046 hectares in 2000 to 100.472 hectares in 2023, highlighting the impact of climate change. Additionally, snowline analysis demonstrates an upward migration, with the 10th percentile snowline increasing at a rate of approximately 5.16 m/year, indicating progressive snow loss at lower elevations. These findings emphasize the vulnerability of UKB’s cryosphere to climate change, necessitating adaptive water resource management strategies to mitigate impacts on hydrology, agriculture, and regional water security.