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Hydrology Department, Water Resources Division, Kuwait Institute for Scientific Research, P.O. Box 24885, 13109 Safat, Kuwait 

ABSTRACT

The quality of groundwater and, hence, the uses of this water are a function of the interactions between the aquifer materials and the water passing through them (water-rock interaction). However, the concentrations of different ions in groundwater depend on the rock mineralogy through which the water passes and the speed of its migration along the flow path. In this study, the Hounslow (1995) simplified mass balance technique was used to deduce the source rock of the Kuwait Group aquifer water in the south western part of Kuwait. In addition, this technique was utilized to identify the major geochemical processes that influence the groundwater quality in the area. The results indicate that the source of Cl^- and Na⁺ ions in the aquifer are from halite dissolution, where Cl^- remains in the water and some Na⁺ ions are removed by reverse ion exchange processes due to the presence of clay minerals in the aquifer materials. The low concentration of SO₄^2- in the aquifer indicates that there is no gypsum or anhydrite to dissolve or enough pyrite to produce SO₄^2-. The relationship between HCO₃^- and SiO₂ indicates that the SiO₂ in this aquifer is due to silicate weathering, suggesting that the material of this aquifer could be hydrolysis-prone rock types, which are secondary products of the chemical breakdown of aluminosilicates such as feldspar. Finally, the ratio of Mg²⁺/Ca²⁺ indicates that carbonate minerals are unlikely to be present in this aquifer (except possibly as a cement for elastic sediments).