Geochemical and multivariate statistical study to assess the salinisation origin of the Remila plain groundwater, Khenchela Algeria

The aquifer system of the Remila plain (Khenchela, Algeria), covering 250 km2, is one of the semiarid regions where groundwater is heavily exploited for urban supply and irrigation. An integrated hydrochemical and statistical analysis was performed on 70 water samples to identify the main processes and the origin of salinisation of our waters. Chemical analyses indicate salinity values (TDS) ranging from 568 to 1586 mg·dm-3 with an average of 869 mg·dm-3, with sulphate being the dominant ions, especially in the north and northeastern parts of the region. The identified chemical facies are SO4-Cl-Ca in the northeastern part, SO4-Cl-Ca-Mg present in most waters, and HCO3-Ca-Mg in the southeastern part. We applied the statistical approach to group the waters into three categories using Principal Component Analysis (PCA) and Hierarchical Clustering Analysis (HCA); 1) saline waters (23%) (TDS > 1000 mg·dm-3 and SO42-dominance), 2) moderately saline waters (51%) with HCO3- dominance, 3) moderately saline waters (26%) with a mixed facies. The binary ion diagrams used suggest that the main hydrochemical processes are: evaporites dissolution and/or precipitation, accompanied by an exchange and/or reverse exchange of ions. Additionally, another process was detected in the northeastern part of the area; the saline intrusion of Sabkha waters, favoured by intensive aquifer exploitation.