Influence of summer snowfall on discharge emanating from the Gangotri glacier

Study of Himalayan glaciers are important for a number of reasons including hydroelectric power, drinking water supply, irrigation & water resources. The aim of this investigation was to determine how summer snowfall events between 2001 & 2004 influenced runoff flowing from Gangotri glacier, located in the Garhwal region of the Himalayas. This was achieved by collating air temperature, precipitation and discharge data for the study area. Data were used to determine the hydrological regime within catchment and to establish the general influence that air temperature and precipitation have on discharge, using regression and correlation analysis. Using a temperature lapse rate the daily average elevation for the 0 °C isotherm was calculated. This differentiated days in which snowfall events would cover a large majority of the glacier through filtering elevation. Correlation analysis was used to assess the relationship between air temperature and discharge; before, during and after these precipitation events. It was found that air temperature was the driving factor for discharge with R2 results ranging from 0.38 to 0.67 for the study period, whereas between discharge and precipitation R2 ranged from 0 to 0.16. Under lowering 0 °C isotherm filters the relationship between air temperature and discharge became weaker for all years apart from 2004, whereas the relationship between discharge and precipitation became more negative for 2001 & 2004. These findings suggest a decreasing influence of air temperature and presence of snowfall, where an increase in precipitation causes a decrease in discharge. During three specific snowfall events correlation between discharge and air temperature before the snowfall event was positive, during the period of snow cover was negative and after the snowpack had depleted returned to a positive correlation. Results show that such snowfall events appeared to have a dampening effect on discharge for around 5 to 7 days