The present study aims to investigate the hydrogeochemical characteristics of the Terminal Complex (TC) groundwater in the Biskra region (north-east Algeria) to understand the hydrogeochemical processes that control their chemical composition using multivariate statistical techniques, bivariate and thermodynamic plots. A total of forty-five (45) water samples were collected from wells exploiting the TC aquifer and analyzed for electrical conductivity, pH, temperature, and major ions (April 2019). The results obtained indicate that the quality of the water does not meet WHO standards for drinking water, with contents of major elements exceeding the standard for most of the wells, except for the wells in the northern part, which are of good quality. Four types of hydrochemical facies were identified, revealing the diversity of processes that control water chemistry in the study area: (i) a sulfate sodium facies (47%), (ii) a sulfate calcium facies (37%), (iii) a bicarbonate magnesium facies (9%) and (iv) a sulfate magnesium facies (7%). Facies (i), (ii) and (iv), highlighted in the southern and south-western parts, are linked to the dissolution of salts and gypsum from evaporite formations. Facies (iii), identified in the northern part, reflects the dissolution of carbonate formations located in the aquifer recharge limits (recharge zone). The application of principal component analysis indicates that Na+, Cl-, Ca2+, Mg2+, SO42- and TDS represent the axis of mineralization. The dissolution of halite, gypsum, and anhydrite-bearing rocks is the primary mechanism for conducting groundwater salinization. These processes are confirmed by the PHREEQC model which reveal that calcite and dolomite precipitation favors the dissolution of evaporites where almost all water samples are undersaturated with respect to gypsum, anhydrite and halite (evaporite minerals). In addition, bivariate plots of the different ions show that cation exchange reactions leading to the adsorption of Ca2+ on clay minerals and simultaneous release of Na+ ions and silicate weathering are also processes that influence the groundwater chemistry of the Terminal Complex aquifer.