Effect of salt domes on hydrochemical characteristics and water quality deterioration of Firuzabad River, Iran

This study was performed to investigate the impact of Jahani, Konarsiah, and Khurab salt domes on the hydrochemical characteristics together with the water quality of Firozabad River. For this purpose, the results of physicochemical parameters of two hydrometric stations before (Dehroud) and after (Dehram) salt domes over a period of 25 years were used. Statistical analysis revealed that there was a significant difference between the hydrochemical characteristics of two stations. Results showed a possible influence of watershed lithology on river hydrochemistry in Dehroud station. While the water samples show a strong tendency to reach seawater chemical composition in Dehram station. This is clearly seen in bivariate plots and stiff diagrams where water samples are mainly grouped into two zones representing their chemical composition. Piper and Durov diagrams indicated the prevailing facies of Ca–Mg–HCO 3 and Na–Cl in Dehroud and Dehram stations, respectively. Simpson ratio results showed that Dehram samples distributed in a severely saline region causing a reverse ion-exchange process in Dehram station. In comparison with Dehram station, Dehroud water samples fall between slightly saline to moderate saline zones resulting in both ion-exchange and reverse ion-exchange processes. Saturation index (SI) results revealed that the SI of evaporative minerals in Dehram station was increased significantly, so that these minerals tend to reach equilibrium. Dehroud station water quality for irrigation purposes was good to excellent. While it was drastically diminished in Dehram station. Similarly, for irrigation purposes, river water quality changes from potable at Dehroud station to non-potable at Dehram station.