SNOWMELT RUNOFF MODELING FOR AN INDIAN HIMALAYAN RIVER BASIN

Abstract

Many of the major rivers in India originate from the Himalayas. These rivers have significant contribution from snow and ice which makes these rivers perennial. More than 3 billion people are benefitted by the food and energy produced in these river basins. The Sharda (Mahakali) River which is a sub-tributary of the Ganga River and originates from the glacier of Zaskara Range in the region of higher Himalayas, near Indo-Tibetan border is one among these rivers. This study has been carried out to model of Snowmelt Runoff in the part of the Sharda (Mahakali) River basin upto NHPC's Tanakpur Barrage by integrating MODIS snow cover data and SRTM digital elevation model (DEM) with Geographic Information System (GIS) and finally into the Windows version of snowmelt runoff model (WinSRM or SRM). The temporal snow cover area (SCA) for the period Oct'2006—Sep'2010 was derived from MODIS Snow Cover data and SRTM DEM was used along with these data to get the snow cover in different elevation zones. SRM is a temperature index-based snowmelt runoff simulation model, and has been widely used in almost all the part of the world for simulating snowmelt runoff. The daily hydro-meteorological data (rainfall, max. & mm. temperature and discharge) procured from NHPC Ltd. was used for simulation of daily runoff at the basin outlet i.e Tanakpur barrage. The model was calibrated with a set of parameters for the period Oct'2006-Sep'2007 and validated for three years (Oct'2007-Sep'2010) using the same parameter values. The Overall accuracy of SRM for part of the Sharda River basin in terms of coefficient of correlation (R2) is in the range of 0.72-0.89 for the period Oct'2006—Sep'20 10. Based on the simulation results, average Snowmelt contribution to the total streamflow computed at Tanakpur barrage in the Sharda River basin is about 16.5%. In this study, SRM - has also been used for assessment of the impact of future climate change on the streamfiow under various hypothetical scenarios of changed climate. The observed increase in total streamfiow on increase of 1°C and 2°C in temperature is about 3.2% and 12.3% respectively for the period Oct'2006 to Sep'2007. It has also been observed that increase in temperature by 2°C (without any change in precipitation) lead to an early snowmelt from March month onwards.