2018 Springer Nature B.V. The main purpose of this study was to evaluate the water quality of the Karoon river, which is a main river in Iran country. For this purpose, hydrochemical analyses of a database that maintained by the Water Resources Authority of Khuzestan Province, Irans Ministry of Energy, were carried out. These data were compared with the maximum permissible limit values recommended by World Health Organization and Food and Agriculture Organization water standards for drinking and agricultural purposes, respectively. Also in this regard, multiple indices of water quality were utilized. However, not all indices gave similar rankings for water quality. According to the USSL diagram and Kelly ratio, Karoons water quality is not suitable for irrigation purposes due to high salinity and moderate alkalinity. However, the results of the magnesium hazard analysis suggested that water quality for irrigation is acceptable. A Piper diagram illustrated that the most dominant water types during the 15 years of the study were NaCl and NaSO4. The mineral saturation index also indicated that NaCl is the dominant water type. The water quality for drinking purpose was evaluated using a Schoeller diagram and water quality index (WQI). According to the computed WQI ranging from 111.9 to 194.0, the Karoons water in the Khuzestan plain can be categorized as poor water for drinking purposes. Based on hydrochemical characteristics, years 20002007 and 20082014 were categorized into two clusters illustrating a decline in water quality between the two time periods.