Physicochemical characterization of El Ouldja valley waters, in the province of Khenchela, eastern Algeria

This work has been carried out at the southern side of the Tabouant anticlinal in El Ouldja valley in the Aures, east of Algeria. The different water tables exploited belong to many lithological entities (evaporitic and carbonated). The combination of geology and statistics has allowed to study the chemistry origin of these waters. This is water of evaporitic and secondarily carbonates origin. The phenomena causing this class are numerous and are essentially linked to the aquifers chemical composition. The chemical analysis of all samples of the area confirms this. Waters salinity is very variable and generally high. Waters electrical conductivity ranges between 1504 and 6150 μS cm− 1. The extreme chemical facies are chloride–sulfate and calcium–sulfate, with a predominance of this latter. Sulfate and chloride contents can locally reach the respective values of 1100 mg/l− 1and 650 mg/l− 1. Thermodynamic analysis indicated the waters saturation with carbonates, calcite and dolomite, because of the degassing and the CO2 dissolution of evolutive formations, gypsum and halite. The crossed binary diagrams suggest that water salination might be attributed to water–rock interaction through the geochemical process of mineral dissolution, precipitation and ions exchange.