Geochemical characteristics and suspended sediments dynamics in the meltwater from the Gangotri Glacier, Garhwal Himalaya, India

The processes of erosion and suspended sediment delivery are important components of runoff originating from a glacier-fed basin. The magnitude of suspended sediments has important implications for channel morphology, material flux, geochemical cycling, and water quality of the river. This study investigates the dynamics of suspended sediment and its mineralogical and chemical characteristics with meltwater draining from Gangotri Glacier during the ablation season of 2012 in relation to hydrology and geology of the basin. Significant variations in suspended sediment concentrations (SSC) and Suspended sediment load (SSL) were observed. The results indicate that there may be a major source (or a few similar sources) of suspended sediment contributing to river discharge over the study site. The concentration of contributing sediment is either diluted by mixing with relatively clean snowmelt water or concentrated by stormwater after interaction with lithology. The major possible source(s) of suspended sediment lies beneath the glacier. In addition, significant variations in relative mineralogy (fine fraction of chlorite, quartz, K-feldspar, and plagioclase) and chemical analyses of alkali and heavy metal (K, Na, Fe, As, Mn, Cu) in the sediment suggest a significant role of subglacial meltwater in controlling the chemical composition of suspended sediment during the ablation season. Snow and glacier melt are the main factors controlling river discharge near the snout of Gangotri glacier. Further, the variability of snow and glacier meltwater due to temperature variation controls the dynamics of suspended sediment concentration.