Satellite-based snowcover distribution and associated snowmelt runoff modeling in Swat River Basin of Pakistan

The snowcover and glaciers of hindu kush-himalayan (hkh) region are one of the largest repositories of inland cryosphere outside polar regions and obviously the lifeline for the people of sub-continent. however,reliable estimates of the snow area extent and snowmelt runoff have been lacking in this largely inaccessible and data sparse region. this is particularly important in view of the climate change impacts on hydrological resources of the region. present study utilized gis,rs and hydrological modeling techniques to estimate spatial and temporal distribution of snowcover; quantified snowmelt and rainfall runoff components; and developed prediction models for snowmelt and river discharges. the results revealed that swat river basin of pakistan is predominantly snowfed,as the annual snowmelt runoff contribution to the total runoff may range 65-75%. a significant effect of snowcover variation was observed on river discharge and snowmelt runoff. snowcover and associated snowmelt runoff remain highly variable throughout the calendar year. snowfall usually starts abruptly in september and october months but the following four main winter months (i.e.,november-february) generally bring in most of the snowfall. snowcover increases from less than 2% of the basin area in august,only at higher altitudes,to about 64% by the end of january or early february. snowmelt generally continues throughout the year but contribution of winter snowmelt runoff is generally very low. unlike snowfall,snowmelt runoff usually progresses gradually and smoothly and is more predictable. the summer snowmelt normally gets momentum in march and increases from around 30-60 m3/sec to 400-760 m3/sec in late june or early july. thereafter,it declines gradually,reducing to 30-50 m3/sec in december. the december-february runoff normally remains the same. © pakistan academy of sciences.