In the Central Anatolia region where precipitation decreases and agricultural and industrial activities are increasing, the pressure on water resources is increasing day by day. The quality and quantity of water resources are important for biological needs, integrated environmental management and sustainable development goals. It is both complicated and costly to determine the water quality by interpreting many parameters affecting water quality at the same time. For this reason, water quality index models are used to provide a better understanding of the water quality. In this study, the water quality of Karasu River, which is one of the important drinking water resources of Aksaray Province, was monitored between December 2015 and November 2016 for one year and the overall water quality of the river was evaluated with 3 different water quality index models. It was determined that NH4-N, BOD5, Co, fecal coliform, Ba, Cu, Zn and dissolved oxygen parameters exceed the limit values of the regulation of drinking water obtained or planned surface water quality and the main parameters affecting the quality of water. In addition, the surface water quality class of water source was determined to be “IV” depending on NO2, B, Cd and Zn parameters. According to the model results, the water quality of the Karasu River was “moderate” according to the National Sanitation Foundation Water Quality Index, “bad” according to the Canadian Council of Ministers of the Environment, and “bad” according to the Oregon Water Quality Index.