Monitoring snow cover change in the Yasin River basin using MODIS snow products and Landsat-derived water indices...

The Indus River basin heavily depends critically on the snow and glacier reserves of the Hindukush-Karakoram-Himalaya (HKH) region, often termed the "third pole." However, rising temperatures and shifting climatic patterns increasingly threaten these snow and glacial reserves, necessitating further scientific investigation. This study analyzes snow cover dynamics in the Yasin River basin using Moderate Resolution Imaging Spectroradiometer (MODIS) Terra Snow Cover 8-Day L3 Global 500-m product (MOD10A2, Collection 6.1) from 2003 to 2023 and Landsat-derived Modified Normalized Difference Water Index for 2003, 2013, and 2023 to assess changes in surface water bodies. Climate data (temperature and precipitation) from the meteorological Station (2003-2023) were incorporated, and statistical relationships were examined using Pearson and Spearman correlation analyses. Results show two distinct decadal patterns: (1) 2003-2012 exhibited a steady decline with a minimum August snow cover area (SCA) of 1432 km², and (2) from 2013 to 2023, summer melt intensified significantly, with August SCA dropping to 1335 km², confirming a climate-driven acceleration of snow loss. This trend aligns with the recorded temperature rise across the HKH region. Winter months maintained high SCA (2655-2600 km²), while summer snow retention declined markedly in the second decade. A strong negative correlation between temperature and SCA (r = -0.88) suggests significant warming-induced snow loss, while precipitation showed a weaker relationship. Concurrently, surface water bodies expanded from 411 km² (2003) to 523 km² (2023), reflecting enhanced meltwater contribution. The study indicates that minor SCA reductions are likely driven by global warming, potentially disrupting the hydrological and ecological balance in the Yasin basin. This study underscores the need for enhanced snow cover monitoring to support climate-resilient water management in vulnerable downstream regions.