Hydrogeochemical Characterization of Groundwater in the Terminal Complex and Intercalary Continental Aquifers, Ouargla, Southeastern Algeria.

Tahar Selmane, Med Hicham Boutelli, Hasnaoui Yacine, Senna Lachehab

Abstract


Groundwater is a crucial resource in arid and semi-arid regions, particularly in Ouargla province, southeastern Algeria, where extreme aridity and chronic water shortages prevail. This study investigates the geochemical processes shaping groundwater quality within two major aquifer systems: the Terminal Complex (TC) and the Intercalary Continental (IC). A multidisciplinary approach was applied, including physicochemical analysis of water samples, hydrochemical facies classification using the Chadha diagram, correlation of major ions, evaluation of mineral saturation indices, and calculation of the Base Exchange Index (BEI). The findings highlight that evaporate dissolution, mainly of halite and gypsum, is the dominant process controlling mineralization. This is reflected in elevated levels of chlorides, sulfates, and sodium in groundwater. Chadha diagram results revealed diverse hydrochemical facies, with Ca-Mg-SO₄ and Ca-Mg-Cl types prevailing, along with a significant Na-Cl signature in the TC aquifer. Cation exchange between groundwater and clay minerals was also identified as an essential mechanism, responsible for sodium enrichment and calcium depletion in several samples, as confirmed by BEI values. Saturation index analysis demonstrated under saturation with respect to halite, gypsum, and anhydrite, supporting their active dissolution, while waters were supersaturated with calcite and dolomite, indicating potential precipitation. Overall, the study concludes that groundwater chemistry in Ouargla is primarily governed by natural mineralization processes and ion exchange reactions. These insights are fundamental for the sustainable management of groundwater resources, particularly for irrigation and other vital uses in this highly water-stressed region.

Keywords: groundwater quality, Ouargla region, geochemical processes, water mineralization, evaporate dissolution, cation exchange

© 2026 Serbian Geographical Society, Belgrade, Serbia.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Serbia.


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