STATISTICAL AND HYDROCHEMICAL CLASSIFICATION OF UNDERGROUND WATERS IN A MULTI-LAYER AQUIFER SYSTEM IN AN ARID ZONE :APPLICATION TO CHOTT EL GHARBI BASIN (EXTREME WEST OF ALGERIA)

Abstract

The studied area, so called Chott El Gharbi shelters a multilayer aquifer system. The hydro-chemical tool shows that the results of the groundwater analyzes of the aquifer system of the Chott El Gharbi region revealed that they are sulphated-calcium and magnesian. Water infiltrated at the Bajo-Bathonian and Mio-Plio-Quaternary carbonate formations is enriched with HCO3-and SiO2 along its underground route. Also, the presence of a Triassic evaporitic formation or the Cenomano-Turonian argilo-gypsum formation enriches these waters with SO42-, Cl-, K+, Mg2+, Na+ and Ca2+.Thermodynamics has shown that these waters are under saturated evaporitic elements, which gives them a greater power of dissolution than that of carbonates which are in equilibrium or sometimes even supersaturated and tend to precipitate.