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 (delta O-18 and delta D) 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 delta O-18 and delta D compositions of the Gomati River water ranged from -1.67 to -7.62 aEuro degrees and -25.08 to -61.50 aEuro degrees, respectively. Deuterium excess values in the river water (+0.3 to -13 aEuro degrees) and the lake water (-20 aEuro degrees) indicate the significance of evaporation processes. Monthly variation of delta O-18 and delta D values of the Gomati River water and the shallow groundwater follows a similar trend, with isotope-depleted peaks for delta O-18 and delta D synchronized during the monsoon season. The isotopically depleted peak values of the river water (delta O-18 = -8.30 aEuro degrees and delta D = -57.10 aEuro degrees) can be used as a proxy record for the isotopic signature of the monsoon precipitation in the Ganga Alluvial Plain.