Hydrogeochemical processes operating within the main aquifers of Kuwait

The study area, Al-Wafra, is located in the extreme south of Kuwait and occ upies an area of 325 km(2). The objective of this study was to develop an i nterpretation and understanding of the geochemical processes and characteri stics of the Kuwait Group and Dammam limestone aquifers. Therefore, hydroch emical data comprising the mean values and standard deviations of the major ion concentrations, pH, PCO2 and 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 irriga tion has been studied through the determination of exchangeable sodium perc entage (ESP), boron, adjusted sodium adsorption ratio (adj. SAR), nitrate a nd 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 d issolution models involving carbonate, sulphate and chloride minerals. The cation concentrations have probably been modified by exchange processes inv olving clay minerals. The ground-water was found to be oversaturated with r espect to calcite, aragonite and dolomite, and undersaturated with respect to gypsum, anhydrite and halite. The calculated mean value of PCO2 is 5 .10 (-3) atm., which suggests a deep, closed environment system. The hierarchic al cluster analysis shows that the ground-water is separated into geochemic al provinces based on the similarity of total dissolved solids. Trace eleme nt concentrations of Pb, Ni, Cd and Zn occur at concentrations below 1.0 mg l(-l), whilst high nitrate values in the Kuwait Group ground-waters (mean = 123 mgl(-1)) indicates the impact of agricultural activity on the study ar ea. 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. (C) 1999 Academic Press