Characterization of processes and mechanisms controlling ground water salinization in the Algerian Sahara
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ORIGINAL PAPER
Characterization of processes and mechanisms controlling ground water salinization in the Algerian Sahara Oualid Melouah 1
&
Hichem Zerrouki 2 & Romina Lucrecia Lopez Steinmetz 3
Received: 14 October 2019 / Accepted: 20 August 2020 # Saudi Society for Geosciences 2020
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 ClSO4-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. Keywords Water quality index . Guerrara oasis . Salinity . Electric tomography . Sulfate minerals
Introduction The Sahara is, as its name in Arabic ا ﺤ ا ا ﻜب ىsuggests, is one of largest hot desert on Earth (~ 9.20 M km2). In arid regions, the balance between rainfalls and hydrogeologic recharge of shallow aquifers is very sensitive to climate variations. From a simplistic point of view, arid conditions (low Responsible Editor: Amjad Kallel * Oualid Melouah [email protected] Hichem Zerrouki [email protected] Romina Lucrecia Lopez Steinmetz [email protected] 1
Laboratoire des réservoirs souterrains Pétroliers, Gaziers et Aquifères, Faculty of Hydrocarbons, renewbales energies and earth planetary sciences, University Kasdi Merbah, Ouargla, Algeria
2
Faculty of Earth Sciences and Architecture, Department of Geology, University Larbi Ben MhidiOum, El Bouaghi BP, 04000 Oum El Bouaghi, Algeria
3
INECOA, UNJU-CONICET, Av. Bolivia 1661, 4600 Jujuy, Argentine
precipitation P and high evaporation E rates, where P < E) induce salinity increases in soils and groundwater reserves. However, factors responsible for salinization are complex and might involve a complex suite of variables such as the lithological characteristics of the geological substrate, the hydraulic gradient, and the ground water pumping and recharge rates (Abdulameer et al. 2018; Kumar et al. 2019). Besides the prevalence of drought conditions, human activity represents an additional stress for hydrological systems, altering its physical and chemical prosperities at the point that, in some places, aquifer waters become
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