Assessing recharge process in plain catchments using isotopic and hydrochemical techniques

Abstract

In order to increase the sustainability and conservation of water resources, a joint approach of isotopic and hydrochemical techniques was attempted to identify and quantify water sources and favourable recharge areas that would explain the integral functioning of a typically plain catchment. Chloride and δ18O and δ2H were measured in rain, groundwater, and pond samples. Chloride mass balance approach was applied to calculate the recharge and mixed water calculation was carried out using conservative tracers. Also, the local meteoric water line was calculated. Depleted isotopic and slightly progressive chloride contents are observed and they are grouped around to the local meteoric water line in the upper part and in the west of the lower catchment. In the East lower area 20% of recharge is calculated; isotopes are more enriched and lower concentration of chloride are observed. Depleted isotopic fingerprint and low salinity concentration for Ballenera pond were identified in a well close to it. This work demonstrates that in very flat zones, small changes in the hydrologic fluxes can impact on the water table of surface waters and groundwaters, leading to establish very local recharge zones that hardly can be recognized in large scale or esatfrequency of measurement, but can quiet easily be identified when chemical conservative tracers and water stable isotopes are used. Also, isotopic data demonstrate the importance of shallow wetlands as certain recharge areas to the regional aquifer, becoming areas of high groundwater vulnerability.