Spatio-Temporal Variability of Snow Cover in Alaknanda, Bhagirathi and Yamuna Sub-Basins, Uttarakhand Himalaya

Advance wide field sensor (AWiFS) data of RESOURCESAT-1 and 2 satellites of IRS series were used to produce snow cover products at 10-day interval from 2004 to 2012 covering October to June of consecutive years for Alaknanda, Bhagirathi and Yamuna sub-basins of Ganga basin in the Himalayan region. The snow products were generated using Normalized Difference Snow Index (NDSI) at a spatial resolution of 56 m using green (B2) and SWIR (B5) channels of AWiFS sensor. Minimum and maximum snow cover was found to be 998, 669, 141 sq. km, and 7874, 5876, 3068 sq. km for Alaknanda, Bhagirathi and Yamuna sub-basins respectively. The areal extent of snow was higher than the mean during the years 2004-2005, 2007-2008 and 2011-2012 for all sub-basins. Mean of monthly fluctuations between maximum and minimum snow cover were recorded as 3105, 2305, 1235 sq. km corresponding to variation in snow line altitude of 1613, 1770, 1440 m respectively. A subtle increase in the snow cover has been observed in these three sub-basins during 2004-2012. The results matched well with the variations in temperature taken from nearby ground weather stations. Snow cover products were analysed to understand spatio-temporal variability of accumulation and ablation of snow in the three sub-basins. Monthly fluctuations in snow cover were high during accumulation period than in ablation. This work also attributes in generation of long-term database which will be useful for understanding climatic variations over Himalayan region.