Agricultural impact on quality and quantity of groundwater in the north-western Ganga plain, India: A stable isotopes and remote sensing approach

Groundwater is the primary reservoir of unfrozen freshwater, a critical element in thewater cycle. It is constantly extracted, which has resulted in irreversible depletion.The significant extraction of groundwater led to a shift in the Earth's rotational poleand has been attributed to global sea level rise, and disruption of the regional energybudget. The extraction has influenced the soil quality and the interaction betweensurface and subsurface water. The Hindon River basin, situated in the north-westernregion of the Ganga plain in India, once witnessed the Indus Valley civilization, isnow facing adverse effects from anthropogenic activities. The groundwater level hasdecreased by over a meter in recent decades, and the concentration of dissolvednitrate, an indicator of pollution, has exceeded safe limits. The pollution ingroundwater has resulted in numerous severe health issues, including cancer andliver disorders. Consequently, it is crucial to comprehend the human-inducedalterations in the water cycle, focusing on identifying pollutant sources and theprocesses responsible for redistribution of water mass among different componentsof the regional hydrological cycle. In this study, we have used remote sensing data inthe Soil and Water Assessment Tool (SWAT) to understand impact of crop patternson regional water budget. Chemical tracers such as stable water isotopes (δD-H2O,δ18O-H2O), dissolved nitrate isotopes (δ15N-NO3 , δ18O-NO3 ), and ionic chemistry [NO3- ]have been used to validate the model results. The initial output of the modelsuggests that changes in existing cropping patterns can improve the discharge in theriver.