TEXTURE AND SUBGLACIAL EVACUATION ANALYSIS OF THE PARTICLE SIZE OF SUSPENDED SEDIMENT FROM THE GANGOTRI GLACIER, CENTRAL HIMALAYA

Hydrological and sedimentological studies of glaciers have been considered worldwide as the subject of significant glaciological research. It becomes extremely important in the Himalayan region where most of the glaciers are debris covered, which can impact ablation and meltwater production. It has been observed that during summer months, the snow and glacier meltwater runoff from Himalayan glaciers transport suspended sediments along englacial, supraglacial, and subglacial pathways at very high rates. However, very limited studies have been carried out in this region to assess characteristics of these glaciers. Most of the studies carried out in this region are based on the determination of correlations of suspended-sediment concentrations in proglacial discharges and their association with meteorological parameters without assessing their origin or evacuation pattern. Consequently, the objective of this study is to determine the temporal variations in the suspended sediment particle size and source of sediment evacuations in the proglacial river originating from the Gangotri Glacier. To accomplish our objective we established relationship between suspended sediment concentration (SSC) and discharge, determined size of sediments, and carried out textural analysis using data from three consecutive ablation period (2004-2006). Results from textural analysis of suspended sediment reveals that mean particle size fraction ranges between 4Φ–6Φ representing poor to poorly sorted with coarse to fine skewed distribution. Particles were found to be symmetrical to positively skewed and kurtosis of mesokurtic to platykurtic. The particle size distribution, which is important to understand because many geomorphologists and sedimentologists widely accept an exponential downstream decline of average particle size in channels, suggests the dominance of silt particles (69–77%) without any significant seasonal variation. Furthermore, discharge and SSC pattern indicates that sediment evacuation relies more or less on the meltwater, which does seem to increase as melt season progresses. Overall, these results indicate specific trend that is related to the subglacial sediment evacuation.