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 the
water 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 pole
and has been attributed to global sea level rise, and disruption of the regional energy
budget. The extraction has influenced the soil quality and the interaction between
surface and subsurface water. The Hindon River basin, situated in the north-western
region of the Ganga plain in India, once witnessed the Indus Valley civilization, is
now facing adverse effects from anthropogenic activities. The groundwater level has
decreased by over a meter in recent decades, and the concentration of dissolved
nitrate, an indicator of pollution, has exceeded safe limits. The pollution in
groundwater has resulted in numerous severe health issues, including cancer and
liver disorders. Consequently, it is crucial to comprehend the human-induced
alterations in the water cycle, focusing on identifying pollutant sources and the
processes responsible for redistribution of water mass among different components
of the regional hydrological cycle. In this study, we have used remote sensing data in
the Soil and Water Assessment Tool (SWAT) to understand impact of crop patterns
on 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 model
suggests that changes in existing cropping patterns can improve the discharge in the
river.