Stable isotope study of the Ganga (Ganges) river system

Abstract

Stable hydrogen (δD) and oxygen (δ¹⁸O) isotope ratios of the Ganga river system are reported for the first time. High-altitude streams (Ganga headwaters) show a δD-δ¹⁸O relationship close to that of the global meteoric water line. Samples from the lowland regions show a significant effect of evaporation, indicated by a reduced slope (of approximately six) in the δD-δ¹⁸O plot. There is a progressive enrichment of the δ values downstream in the Ganga. The δ values of the Ganga headwaters show a change of −0.19%. (δ 18O) and −1.6%. (δD) per 100 m increase in altitude (the 'altitude effect'), which is shown by a simple theoretical calculation to be half that in the local precipitation.