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

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 Ca2+ > Na+ ≈ Mg2+ > K+ and HCO3+>Cl->SO42->NO3-. With increased water–rock interaction, waters in groups 2 and 3 become more saline, changing composition towards Cl–HCO3–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: (1) dissolution of evaporite minerals; (2) precipitation of carbonate minerals, quartz, kaolinite and Ca-smectite; (3) ion exchange.

► Study of groundwater. ► Application of multivariate statistical methods. ► Application of geochemical modeling in groundwater.