Structural control on groundwater hydrogeochemistry and recharge processes in the semi-arid Chemora Plain (northeastern Algeria): Insights from hydrochemistry, stable isotopes and multivariate statistics
Abstract
Understanding the factors controlling groundwater mineralization is essential for the sustainable management of water resources in semi-arid environments. This study investigates the hydrogeochemical functioning of the Chemora Plain aquifer (northeastern Algeria), where a Cretaceous structural ridge divides the alluvial basin into northern and southern hydrogeological compartments. A multidisciplinary dataset combining major-ion hydro-chemistry, water hardness, mineral saturation indices, stable isotopes (δ¹⁸O and δ²H), and principal component analysis (PCA) was used to test the hydrogeochemical significance of this structural organization. Electrical con - ductivity, hardness and major-ion distributions reveal differentiated groundwater evolution between the southern and northern compartments, while comparable EC values near the structural boundary indicate that the compart - ments are not completely isolated. Saturation indices show near-equilibrium conditions for carbonate minerals and persistent undersaturation with respect to gypsum, anhydrite and halite, supporting continued water–rock interaction and a potential contribution of evaporite dissolution to mineralization. Stable isotope compositions (δ¹⁸O = −8.96 to −5.89‰; δ²H = −54.98 to −39.10‰; d-excess = 7–17‰) indicate a predominantly meteoric recharge source with limited isotopic modification. PCA further identifies distinct hydrochemical associations for the north - ern and southern sectors, while shared variables indicate partial hydraulic connectivity. The integrated evidence supports a conceptual model in which the Fedjoudj–Bouarif Cretaceous ridge acts as a major structural threshold, whereas the western breach permits localized hydraulic exchange. The main contribution of this study is therefore the demonstration of a structurally controlled hydrogeochemical evolution in the Chemora aquifer through the convergence of independent geological