Groundwater chemistry origin and quality assessment of the Sahel-Soummam aquifer, in northeast Algeria: A combined hydrochemical and isotopic approach

The Sahel-Soummam Wadi plain aquifer in northern Algeria holds significant groundwater resources, supporting irrigation and industrial water supply and contributing significantly to the social and economic growth at the regional scale. However, the increased aquifers' exploitation constitutes a dual challenge about water stress and groundwater's chemical quality. For this purpose, the groundwater quality was assessed by integrating hydrogeochemical and isotopic analysis with statistical methods. The hydrochemical analysis revealed three distinct water facies: Ca-Mg-Cl-SO4, Ca-Mg-HCO3, and Na-K-Cl-SO4 water types. The calcium, sodium, and magnesium concentrations in several samples exceeded the WHO potability standards. The potassium contents in the sampled groundwater were within the WHO guidelines. Chloride, bicarbonate, sulfate, and nitrate concentrations were within the WHO standards. Using graphical, multivariate statistical methods and the isotopic approach highlighted the hydrochemical processes governing groundwater salinization. These processes include evaporation, water-rock interaction involving evaporite mineral dissolution, silicate weathering, and cation exchange. Overall, the groundwater quality assessment classified the samples into excellent (7.5%), good to poor (80%), and very poor to unsuitable (12.5%). Furthermore, the evaluation of groundwater suitability for irrigation revealed varying quality, ranging from good to poor (57.5%) and poor to unsuitable (42.5%). Isotope contents displayed a range of variations characterizing waters originating from a mixture of Atlantic, Western, and Eastern Mediterranean atmospheric vapor masses, with variable potential contributions from those sources.