EFFECT OF SNOW AND GLACIER CHANGES OVER THE HIMALAYAN WATERSHEDS

Abstract

An assessment of the seasonal and annual changes over the Himalayan glaciers is of increasing interest due to its significant impact on the global population living downstream. So, in order to assess the changes in snow and glacier melt runoff a study was conducted on Ganga River basin up to Joshimath using a semi-distributed hydrological model Soil and Water Assessment Tool (SWAT) and the calibration and optimization was done using SUFI-2 algorithm in SWAT-CUP with monthly streamflow data for 1993-2003. The average yearly contribution of snowmelt, rainfall and baseflow was estimated from the basin with a Modified Nash Sutcliffe Efficiency (MNSE) between the estimated and observed discharges of 0.54 and Coefficient of Regression (R²) of 0.536 at the outlet. The yearly variation of Snowfall and Snowmelt was also studied using trendline charts for past years from 1993 to 2003 which showed a decline in this period. It was found that nearly 22% of the entire precipitation takes place as snowfall. Average monthly snowmelt contribution is about 27.5% of the total runoff. The water balance components such as water yield, evapotranspiration was computed to analyze the behavior of various hydrological processes in a snow glacier induced catchment in which water yield constitutes to about 63% of the total annual precipitation. We need to strengthen our spatial and temporal hydrometeorological database to improve the modeling of Himalayan watersheds.