Hydrochemical characterization of the Silifke Plain coastal aquifer was accomplished in this research in order to investigate the water quality of groundwater. The aquifer is located along the Mediterranean coast and forms one of the most productive aquifers in Turkey Groundwater samples were collected from the aquifer as monthly between December 2007 and November 2008 for 12 months. Twenty one artesian wells were chosen and water sampling was made once a month The values of electrical conductivity (EC) and pH as well as main anions and cations were determined twice for each month Based oil the observations in the water wells, the EC, sodium adsorption rate (SAR). and chloride (Cl-) concentrations varied between 437 and 3480 mu S/cm, 0 13 and 23 1. and 25 and 1661 mg Cl-/L, respectively Deterioration of water quality was observed ill some areas very close to the sea due to seawater intrusion and intense use of groundwater for irrigation Crown Copyright (C) 2009 Published by Elsevier B V. All rights reserved