Characterization of processes and mechanisms controlling ground water salinization in the Algerian Sahara

Abstract

This study assesses mechanisms responsible for the aquifer salinization in the Guerrara oasis, in southern Algerian Sahara. Here, underground hydrological resources are indispensable for the local inhabitants. To determine the probable causes of ground water deterioration, 54 water samples were collected from pumping wells and were analyzed in order to characterize their major ion hydrochemistry and to compute indexes on water quality. Additionally, geophysical investigations involved electric resistivity surveys that were applied to investigate the aquifer substrate. Data revealed presence of water at 2m in depth with the presence of, at least, four salt layers that are characterized by very low resistivity values. The aquifer waters are of the Cl-SO4-Ca (Mg) and Cl-SO4-K (Na) types. Due to the prevalence of high saline and sulfurous contents (from 288 to 3134mg/l), water quality is not suitable for agricultural and drinking water uses. Our observations revealed that it would be not only the effect of aridity, but also the dissolution of the underlying ancient evaporates that are suspected to rule groundwater salinization.