The Himalayan mountain system is the source of one of the world's largest supplies of freshwater, as all the major south Asian rivers originate in the Himalayas and their upper catchments are covered with snow and glaciers. There have been no studies describing large-scale pattern of snowmelt over this region. In order to develop a physically based distributed snowmelt-runoff model, a study on the variability of snowfall and snowmelt in the Himalayas is essential. Therefore, for the first time, a study on the variability of snow accumulation and ablation has been undertaken for this region. Remotely sensed snow water equivalent (SWE) from the National Snow and Ice data Centre (NSIDC) and surface temperature data from the Climate Forecast System Reanalysis (CFSR) have been used to study the snowmelt process in the Himalayas. It is seen that, in April, snowmelt mostly occurs in Afghanistan and northern parts of Jammu and Kashmir. Along the Pir Panjal range, snowfall continues in April. Maximum runoff from snowmelt in Kashmir, Himachal and Uttarakhand occurs in the months of June and July. The degree day factor (snowmelt coefficient) indicating snowmelt rate has been computed and it is found that there is large spatial variations in snowmelt rate over the Himalayas due to variations in surface temperatures, accumulated snow amount and elevation. The melt rate ranges from 0.02 to 0.6 cm/oC/day in June. Around the Pir Panjal range and the Satluj basin, the melt rate is higher than other places.
