HYDROLOGICAL CHARACTERISTICS OF THE DOKRIANI GLACIER IN THE GARHWAL HIMALAYAS

Observations of discharge, temperature and suspended sediment made at a gauging site established near the snout of the Dokriani glacier in the western Himalayan region are presented. These observations were made during a scientific expedition to this glacier over 21 days (23.8.1992-12.9.1992). Because of harsh weather conditions, observations could not be made for a longer period. The minimum streamflow in the glacier melt stream was observed at 0700 h whereas the maximum was observed at 1800 h. The ratio of maximum to minimum flow was computed to be 1.81 from the continuous hourly observations. Based on an analysis of the recession of the hydrograph, it was found that the meltwater time lag from the accumulation zone of the glacier was more than seven times higher than that from the ablation zone. No specific relationship was observed between suspended sediment and discharge. The average values of the suspended sediment concentration and load were found to be 350 ppm and 180 t day(-1) respectively, for the study period. Weathering processes in different zones of the glacier were also studied to find out the source of the sediment transported by the meltwater into the melt stream. A high correlation coefficient (r = 0.89) was found between the glacier specific runoff and the air temperature at the gauging site. It showed that temperature alone can represent the melting of the glacier and may be considered for the hydrological modelling of glacier melt runoff. Based on observations over three days under clear weather conditions for isolated snow blocks, the average snowmelt factor was computed to be 5.4 mm/(degrees C. 6 h).