Assessment of snow cover change and its impact on surface runoff due to climate change in the Himalayas

The Himalayan rivers - the Indus, Ganges, and Brahmaputra play a key role in the availability of water resource that affect a significant portion of the South Asia population. The purpose of this study was to explain the reasons for changes in snow cover (mainly climatic variables) and its impact on river discharge of the Himalayas, spreading across five Asian countries (India, Nepal, Bhutan, China, and Pakistan) since last 20 years (2000-2019). We used Terra Moderate Resolution Imaging Spectrometer (MODIS) product (MOD10A2 version 6), Passive microwave (PM) measurements that are sensitive to snow water equivalent (SWE), Global Land Data Assimilation System (GLDAS), GTOPO30 Digital Elevation Model (DEM), surface runoff, and climate datasets. Snow cover area (SCA) showed gradual increase with increasing elevation and slope in all seasons except in winter. In the northwest part of the high elevation zone (>3000 m), SCA trend showed increase while the correlation between SCA and precipitation, and SCA and temperature were positive and negative on an annual time scale respectively. Mean anomaly of runoff in the Ganga - Brahmaputra was negative. From this study, the inter-annual and intra-seasonal variability and the spatial variability of snow cover and surface runoff in the Himalayas will help to plan for improved management of water resources in the future.

Keywords: Himalaya, snow cover, MODIS, GLDAS, climate change.