Assessment of system characteristics of Gangotri glacier headwater stream

Abstract

The study examine the major ion chemistry and p(CO2) variations of Ganga headwater stream for a stretch of 18 km from Gangotri glacier snout at Gomukh to Gangotri for characterising the open and closed system conditions and its temporal variations. The study has been carried out at three locations along the streamcontinuum, at the glacier snout (0 km), Bhojwasa (4 km) and Gangotri (18 km) covering three consecutive melt seasons from the year 2014 to 2016 and reveals the persistence of closed systemconditions along the streamstretch. The year 2014 and 2016 melt seasons experience high p(CO2) closed system conditions associated with high suspended sediment flux, whereas the year 2015 experienced lowp(CO2) closed systemcondition associated with low sediment flux suggesting in-streamsulphide oxidation during high sediment flux years and results into lowvalues of the C-ratio. On the other hand, themelt seasonwith lowsediment flux such as the year 2015 showed dominance of HCO3 − over SO4 2− and higher C-ratio. The study shows that the headwater reach of River Bhagirathi from Gomukh to Gangotri has prevalence of high p(CO2) closed system characteristics associated with high sediment flux and dominance of SO4 2− during the seasonal peak flow. This is suggested as a unique characteristic of the meltwaters of the upper Bhagirathi basin.