Changes in the quality of karstic water resources affected by the proximity to sources of salinity such as evaporate formations and oil brine pose major challenges to such water resources, especially in Khuzestan province, Iran. The karstic water resources of the Kamarderaz anticline plunge in Izeh city in Khuzestan province have hampered water supply management in the region. To determine water quality and the causes of water salinity in the study area, the hydrochemical parameters of the existing water resources were accordingly evaluated. To conduct hydrochemical studies, 21 samples were collected from different water sources of Kamarderaz anticline plunge in 2017–2018. To analyze the garnered data, Piper and Durov diagrams, composite graphs, ion exchange graphs, ion correlation diagrams, salinity source diagrams and ion ratios were used. The results showed that SO42−, Cl−, and Ca2+ in the water resources of the study area were likely due to several sources including carbonate minerals, gypsum dissolution, anhydrite, halite as well as oil brine. Besides, Br/Cl, I/Cl ion ratios as well as Br-Cl and SO4-Cl diagrams revealed the mixing of karstic freshwater with oil brine in the region. The result of TOC analysis also showed that hydrocarbon materials were present in the well of Atabaki (WT). Moreover, elemental sulfur and sulfur isotope analysis showed that the process of thermochemical sulfate reduction or bacterial sulfate reduction in the presence of hydrocarbons produced H2S gas, and eventually penetrated the WT and WH1.