Hydrogeochemical processes operating within the main aquifers of Kuwait

Abstract

The study area, Al-Wafra, is located in the extreme south of Kuwait and occupies an area of 325 km2. The objective of this study was to develop an interpretation and understanding of the geochemical processes and characteristics of the Kuwait Group and Dammam limestone aquifers. Therefore, hydrochemical data comprising the mean values and standard deviations of the major ion concentrations, pH, P CO2and saturation indices for calcite, dolomite, gypsum and halite have been determined in the ground-waters. In addition, the suitability of the brackish ground-water of the two aquifers for irrigation has been studied through the determination of exchangeable sodium percentage (ESP), boron, adjusted sodium adsorption ratio (adj. SAR), nitrate and several trace metals.Chemical analyses of the samples have been interpreted with regard to their saturation levels of calcite, gypsum, halite and dolomite, and by simple dissolution models involving carbonate, sulphate and chloride minerals. The cation concentrations have probably been modified by exchange processes involving clay minerals. The ground-water was found to be oversaturated with respect to calcite, aragonite and dolomite, and undersaturated with respect to gypsum, anhydrite and halite. The calculated mean value of P CO2is 5 · 10−3atm., which suggests a deep, closed environment system. The hierarchical cluster analysis shows that the ground-water is separated into geochemical provinces based on the similarity of total dissolved solids. Trace element concentrations of Pb, Ni, Cd and Zn occur at concentrations below 1·0 mg l−1, whilst high nitrate values in the Kuwait Group ground-waters (mean=123 mg l−1) indicates the impact of agricultural activity on the study area. Ground-water proved to be of rather poor quality, though it is used for irrigation due to the limited natural water resources in arid Kuwait.