Geological controls on water quality in arid Kuwait

Abstract

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 CaSO4water types. Fresh water of Na2SO4, Ca(HCO3)2and NaHCO3water 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 anti-cline structure, where the total dissolved solids ranges from 10,000–115,000mgl−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 ofPCO2for the fresh and brackish water fields are 4 × 10−3and 5 × 10−3(atm), respectively, indicating that the ground-water becomes charged with CO2during infiltration processes. Generally, the salinity increases from 3000–100,000mgl−1in the direction of regional flow.