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 (δ 18 O 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 δ 18 O 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 δ 18 O and δD values of the Gomati River water and the shallow groundwater follows a similar trend, with isotope-depleted peaks for δ 18 O and δD synchronized during the monsoon season. The isotopically depleted peak values of the river water (δ 18 O = −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.