GEOCHEMICAL EVOLUTION OF GANGOTRI GLACIER SYSTEM

Abstract

Gangotri glacier is the biggest glacier in the Ganga basin. River Ganga originates from this Gangotri glacier. The meltwater of the rivers originating from the Himalayan glaciers arecharacterized by its low ionic concentrations and play a major role in diluting the high soluteload emanating from Ganga plain catchments. So, any change in the quantity and qualityof the Himalayan tributaries of River Ganga under the climate change regime will impact thequality parameters of River Ganga as well. Understanding of low temperature soluteacquisition processes is therefore very important for assessing the solute acquisition andpollutant loading further downstream. Therefore, the study of major ions and trace metals insnow and glacier meltwater from the Himalaya has a special significance. Considerable workhas been carried out by different investigators on major ion chemistry of meltwater ofGangotri glacier but little is known about the chemical processes involved in glacial sedimentand meltwater interaction in the Gangotri glacier catchment. Under this project, the studywas carried out along the 14 km stretch from the source at Gomukh to Gangotri town. The magnitude and processes of solute acquisition by dilute melt water in contact with suspended sediments in the channelized components of hydro glacial system have been investigated through a suite of controlled laboratory experiment. With the availability of field data from Gangotri, dissolution experiments of glacial meltwater- sediment interaction conducted on bedsediments of River Bhagirathi considering different operating variables like contacttime, seasonality, different sediment particle sizes, different sediment dose, and crushing of bed sediments revealed the role of sediment in low temperature solute acquisition process characterized by sudden release of ions from the sediment in the initial few seconds. Surface characteristics of sediments play an important role in solute acquisition during freshly grinded sediment-meltwater interaction, which is revealed from progressive increase in solute acquisition process. To acquire the percentage data of the oxides of major and trace elements, XRF analysis were done for suspended and bed sediment samples collected from the field. Also variation of pH,water temperature, electrical conductivity, TSS(Total Suspended Sediments) at three different locations downstream River Bhagirathi have been investigated.These data have major applications on hydrological interpretations based on the solute content of glacial meltwater,geochemical denudation rates,and solute provenance studies.