Investigation on the hydrodynamics of Ganga Alluvial Plain using environmental isotopes: a case study of the Gomati River Basin, northern India

An investigation using environmental isotopes (δ18O and δD) was conducted to gain insight into the hydrological processes of the Ganga Alluvial Plain, northern India. River-water, shallow-groundwater and lake-water samples from the Gomati River Basin were analyzed. During the winter season, the δ18O and δD compositions of the Gomati River water ranged from −1.67 to −7.62 ‰ and −25.08 to −61.50 ‰, respectively. Deuterium excess values in the river water (+0.3 to −13 ‰) and the lake water (−20 ‰) indicate the significance of evaporation processes. Monthly variation of δ18O and δD values of the Gomati River water and the shallow groundwater follows a similar trend, with isotope-depleted peaks for δ18O and δD synchronized during the monsoon season. The isotopically depleted peak values of the river water (δ18O = −8.30 ‰ and δD = −57.10 ‰) can be used as a proxy record for the isotopic signature of the monsoon precipitation in the Ganga Alluvial Plain.