Hydrogeochemical zonation for groundwater management in the areawith diversified geological and land-use setup

Abstract

Despite its limited aerial extent, the National Capital Territory (NCT) Delhi, India, has diversified geologi-cal and topographical setup. A geochemical assessment of prevailing conditions of aquifer underlying theNCT was attempted and further classified into different hydrogeochemical zones on the basis of statis-tical and analyses and its correlation with land use, geological and climatic setting. Mineral phase studyand isotopic analyses were used for the verification of performed clustering. Saturation indices (SI) cal-culated using the geochemical modelling code PHREEQC were used to distinguish the characteristics offour zones, as saturation states of the water does not change abruptly. Four different hydrogeochemicalzones were statistically identified in the area: (1) intermediate (land-use-change-impacted) rechargezone, (2) discharge (agriculture-impacted) zone, (3) recharge (ridge) zone, and (4) recharge floodplain(untreated-discharge-impacted) zone. The distinctiveness of hydro-geochemical zones was further ver-ified using stable isotopic (2H and18O) signature of these waters. GIS-based flow regime in associationwith long-term geochemical evidences implied that these zones are being affected by different prob-lems; thus, it necessitates separate environmental measures for their management and conservation.The study suggested that in a diversified urban setup where the complex interactions between anthro-pogenic activities and normal geochemical processes are functioning, hydrogeochmical zoning basedon the integration of various techniques could be the first step towards sketching out the groundwatermanagement plan.