Abstract

This study investigates the relationships between hydrological and meteorological data collected near the snout of Gangotri Glacier, Indian Himalayas for the different ablation seasons (May - October). The complete analysis employs a hydro- meteorological data series for a period of 7 years (2000 - 2006). The first 5 years data (2000 - 2004) was used for determining correlations, lag-cross-correlations and multivariate regression analyses between daily mean discharge, daily mean temperature and daily rainfall , whereas, last 2 years data (2005 - 2006) was used to simulate the  daily discharge using established relationship. Changes in correlations between discharge and meteorological variables, lagged by 0 - 3 days, were determined. Variations in the physical features of the glacier, weather conditions, and precipitation and its distribution with time over the basin account for changes in correlations. The analysis suggests a very high discharge auto-correlation for each individual year and for the combined data series of 5 years. The substantial storage of melt water in the glacier body and its delayed response of the runoff attribute to the high dependency of a particular day discharge on its pervious day’s discharge. A comparison of correlations between discharge and temperature, and discharge and rain shows that temperature has a better correlation with discharge series for all the years. To estimate the discharge for Gangotri Glacier basin, multiple linear regression equations were developed separately for each ablation season and a combined data set of 5 ablation seasons. The generalized regression equation developed using stepwise regression approach for the data set of 5 years (2000 - 2004) was adopted to estimate daily mean discharge for 2005 and 2006. For both simulation years, the simulation efficiency was very high (R²= 0.96). It is found that discharge of study basin is well represented Q_i-1 (1-day lagged discharge) and T_i, T_i-1, T_i-2 (0 - 2 days lagged temperature) and R_i (0-day lagged rain). Such relationships can be used for filling the missing discharge data as well as for forecasting of discharge.

Key words: Gangotri Glacier basin, Himalayas, glacierized basins, meteorological variables, estimation of melt-runoff.