Abstract:
Groundwater depletion has been widely studied in northwest India, but water quality concerns are still poorly
constrained. In this study, we explore the hydrochemistry of the top 160 m of the aquifer system, through detailed
field studies in the Bist-Doab region, considering both anthropogenic and geogenic controls. A detailed
comparison is made between sites dominated by urban and agricultural landuse. Salinity, nitrate, chloride and
lead concentrations are significantly higher in the shallow (0–50 m) groundwater systemdue to surface anthropogenic
contaminant loading fromagricultural and urban sources. The widespread occurrence of oxic groundwater
within the aquifer system means that denitrification potential is limited and also enhances the mobility of
seleniumand uraniumin groundwater. Geogenic trace elements (e.g. As, Se, F), are generally found at concentrations
below WHO guideline drinking water values, however elevated U concentrations (50–70 μg/L) are found
within the deeper part of the aquifer and shallow urban aquifers associated with higher bicarbonate waters.
Higher concentration of Se (10–40 μg/L) are found exclusively in the shallow groundwater system where Se is
mobilised from soils and transported to depth in the shallow aquifer due to the prevailing oxidising aquifer conditions.
New evidence from a range of environmental tracers shows elevated concentrations of anthropogenic
contaminants in the deeper part of the aquifer (50–160 m deep) and demonstrates vulnerability to vertical migration
of contaminants. Continued intensive groundwater abstraction from N100 m deep means that water
quality risks to the deep aquifer system need to be considered together with water quantity constraints.
