SNOWMELT RUNOFF MODELING AND IMPACT OF CLIMATE CHANGE IN THE HIMALAYAN RIVER BASIN

Abstract

Abstract. Snowmelt from the Himalaya is the major source of groundwater recharge and dry season runoff of all the perennial rivers of Nepal supplying fresh water for drinking, irrigation and hydropower generation. A major proportion of flow in the Karnali River of Nepal is contributed by its snow and glacier-fed river catchments. However, accurate estimation of snowmelt contribution in these rivers is essential for effective management of water resources. Looking to the above, Snowmelt Runoff Model (SRM) was applied to the Karnali River basin to estimate its daily discharge and determine the snow melt contribution of the runoff in this study. Further, climate change impact on the runoff was also studied considering different projected climate change scenarios. Satellite remote sensing data of MODIS 8-day snow cover product was used to derive daily snow cover area of the basin. The coefficient of determination (R2) and the volume difference (Dv) were employed to assess the model performance. The coefficient of determination (R2) was found to be 0.92 and 0.89 for model calibration and validation respectively. Similarly, volume difference (Dv) was found to be -0.87% and 0.94% for model calibration and validation respectively. Study reveals that the runoff volume and average discharge of the Karnali River may increase by about 19% in case of average temperature rise of 4oC and precipitation increase of 20%. Study suggested that the SRM model can be successfully applied in the Karnali river basin particularly and other Himalayan Catchments of Nepal in general for estimation of runoff contribution by snow and glaciers for effective water resources management.