Geological controls on water quality in arid Kuwait

The objective of the study was to assess water quality of the Kuwait Group aquifer and outline the role of geological factors and processes and the subsurface structure on controlling the trend in water quality as discharge-recharge relations. Field pH, temperature and content of Ca2+, Mg2+, K+, Na+, Cl-, SO42- and HCO3- have been determined for 167 ground-water samples of the Kuwait Group aquifer. Hydrochemical characteristics of the study fields were investigated by means of extensive data processing in the form of equivalent per million percentage, equilibrium studies, as well as multivariate statistical analyses. It is found that the Kuwait Group aquifer is mainly occupied by brackish, NaCl and CaSO4 water types. Fresh water of Na2SO4, Ca(HCO3)(2) and NaHCO3 water types occurred in the upper part of the Dibdibba Formation of the Kuwait Group. In addition, saline-brine ground-water is found in residential areas located east of Ahmadi anticline structure, where the total dissolved solids ranges from 10,000-115,000 mg l(-1). A computer program, WATEQ, was utilized to compute the saturation indices of minerals with respect to a given water composition. It is found that the ground-water is supersaturated with respect to calcite, aragonite and dolomite, and undersaturated with respect to anhydrite, gypsum and halite. Calculated mean values of PCO2 for the fresh and brackish water fields are 4 x 10(-3) and 5 x 10(-3) (atm), respectively, indicating that the ground-water becomes charged with CO2 during infiltration processes. Generally, the salinity increases from 3000-100,000 mg l(-1) in the direction of regional flow. (C) 1998 Academic Press Limited.