Comparative Evaluation of NSFWQI and IRWQISC Indicators in River Quality Assessment

This study aimed to evaluate and compare the two water quality indicators NSFWQI and IRWQIsc on the rivers of the five basins of Khuzestan, namely Karun, Karkheh, Dez, Marun-Jarahi, and Zohreh-Hindijan using data recorded in the years of 1390 to 1396. This study shows the differences between the two methods as well as the validation of the water quality index developed in Iran. While according to the NSFWQI index, the rivers of the region are in average condition in terms of quality and there is no particular problem except for points on the Karun River, there is no particular problem; the IRWQIsc index evaluates the status of surface water quality in the province as moderate to poor. Examining the differences between the two indices, it was concluded that the use of the electrical conductivity parameter in the IRWQIsc index has led to the detection of bad areas in terms of quality. The NSFWQI index has been successful in identifying points of high pollution around Ahvaz, while the IRWQIsc index has been successful in identifying points of high salinity on the Zohreh and Jarahi rivers. In determining the spatial distribution of the indicators, three methods were used: spline, kriging, and inverse distance weighting method, which based on the evaluation of the results, the last one was selected.