Geochemical evolution of groundwater in an alluvial aquifer: Case of El Eulma aquifer, East Algeria

Abstract

Hydrochemical, multivariate statistical and inverse hydrogeochemical modeling techniques were used to determine the main factors and mechanisms controlling the chemistry of groundwaters in the El Eulma Mio-Plio-Quaternary aquifer, East Algeria. Cluster analysis based on major ion contents defined three main chemical water types, reflecting different hydrochemical processes. The first, group 1, has low salinity (mean EC= 937 μS/cm) and abundance orders Ca 2+> Na+≈ Mg 2+> K+ and HCO 3+> Cl-> SO 4 2-> NO 3-. With increased water–rock interaction, waters in groups 2 and 3 become more saline, changing composition towards Cl–HCO 3–Ca and Cl–Ca–Na types. The PHREEQC geochemical modeling demonstrated that relatively few phases are required to derive water chemistry in the area. In a broad sense, the reactions responsible for the hydrochemical evolution in the area fall into three categories