Tomographic, hydrochemical and isotopic investigations of the salinization processes in the oasis shallow aquifers, Nefzaoua region, southwestern Tunisia

Abstract

An electrical imaging tomography survey was carried out to identify the lateral and vertical salinity distribution in the oasis shallow aquifers of the Nefzaoua region located in southwestern Tunisia. In addition, hydrochemical and isotopic data were examined to determine the main factors and mechanisms controlling the groundwater chemistry and salinity. Locally, with respect to salinization processes, electrical imaging tomography results show that the storage basins of irrigation excess-water contribute to the increase of the salinity for the major part of the oasis nearby these basins. Major elements distribution and saturation indices indicate that dissolution of evaporites (halite, anhydrite and gypsum) is the main process controlling the groundwater mineralization. Isotopic data highlighted the effect of evaporation in the salinization of these waters. The correlation between the oxygen 18 and the chlorides data confirms the importance of evaporation effect and dissolution as main processes controlling the groundwater mineralization.