The aim of this study is evaluate water quality of the Aksu River, the main river recharging the Karacaoren-1 Dam Lake and flowing approximately 145 km from Isparta province to Mediterranean. Due to plan for obtaining drinking water from the Karacaoren-1 Dam Lake for Antalya Province, this study has great importance. In this study, physical and chemical analyses of water samples taken from 21 locations (in October 2011 and May 2012, two periods) through flow path of the river were investigated. The analysis results were compared with maximum permissible limit values recommended by World Health Organization and Turkish drinking water standards. The water quality for drinking purpose was evaluated using the water quality index (WQI) method. The computed WQI values are between 35.6133 and 337.5198 in the study. The prepared WQI map shows that Karacaoren-1 Dam Lake generally has good water quality. However, Water quality is poor and very poor in the north and south of the river basin. The effects of punctual and diffuse pollutants dominate the water quality in these regions. Furthermore, the most effective water quality parameters are COD and Mg on the determination of WQI for the present study. (C) 2017 Elsevier B.V. All rights reserved.