Role of subglacial system in controlling the hydro-chemistry of Gangotri glacier system in Garhwal Himalaya

Abstract

Role of subglacial system in controlling hydro-chemistry of Gangotri glacier system has been assessed during the period 2014-2016. Discharge hydrographs of the year 2014 and 2015 show sharp rising and falling limb and persistent high flow period covering entire month of July. The delay in peak discharge in the year 2015 may be attributed to the delayed snowmelt from higher elevations of the Gangotri catchment as revealed from the assessment of snow cover variations during different years of the study period. The discharge characteristics in a glacial system have direct bearing on the sediment transfer characteristics. It is also linked with the development and progression of subglacial channel network as subglacial zone is the major source area of glacial sediments. The sediments, which get deposited throughout the winter period gets evacuated during the early stages of subglacial channel development. In 2014 and 2016, this early evacuation of sediment is clearly visible in the data. However, the year 2015 did not experience any significant sediment evacuation neither during the initial stage nor later. In the year 2014 and 2016, HCO3 concentration did not show any significant seasonal variations as expected of a glacial system while during the year 2015, high HCO3 concentration associated with a delayed discharge peak. During 2014 and 2016, SO4 concentration did not show significant seasonal variation as in the case of HCO3. But during 2015, SO4 concentration is attenuated during seasonal high flows suggesting reduced transit time within the subglacial zone supporting our observation that the subglacial system is under developed during 2015.