Groundwater - Surfacewater Intermixing Model and Recharge Conditions in Delhi Area as Derived from δ¹⁸O and δD

Abstract

The data on oxygen-18 and deuterium content in Delhi groundwater show a wide range and indicate that a selection effect in favour of water depleted in stable isotope plays an important role in recharging groundwater adjacent to canal and river. Wide range of stable isotope composition of rainwater in the area and inhomogeneity of the rainfall recharge to the groundwater, as well as mixing of water through different flow paths result in spatial variation in stable isotope content of groundwater. By adopting a very simplified model of equal inflow through the screens to the well with depth, the isotopic gradient with depth has been determined. This simple model on depth variation of stable isotopic content in groundwater indicates contribution of canal water and river water to the groundwater to a considerable depth of the aquifer system. There is a large variation in salinity of groundwater. There is an isotope and chloride content gradient in the upper shallow groundwater, seem to be caused due to diffusion of water from shallow aquifers.