| Description |
Snow from the Hindu Kush Himalaya (HKH) significantly contributes to the water resources that millions depend upon downstream, and therefore, it is important to understand how snow patterns are changing over time in this region. This study uses daily, gap-filled spatially and temporally complete (STC) MODIS Snow Cover and Grain Size (MODSCAG) data to examine trends in snow cover duration and snow cover extent across the HKH from 2002 to 2017, using metrics referred to as snow covered days (SCD) and fractional snow covered days (fSCD). Annual snow cover trends are determined for the entire HKH as well as each major basin and 1,000-meter elevation bands. A modified Mann-Kendall test is used to detect trends within the data, and Sen's slope is applied to measure the magnitude of these trends. Results include significant negative trends in SCD across the entire HKH region, with the highest rate of decline in the Brahmaputra basin. Stable trends are observed at the highest elevations, with the exception of the Ganges in which a significant decline is observed above 8,000 meters, though this is <0.1% of basin area. The Indus, which is influenced by both the westerlies and the monsoons, contains both positive and negative trends in snow cover duration across elevation bands, although trends are not statistically significant. The Syr Darya is the only basin to contain a significant negative trend in fSCD. |
