Background: Water quality is increasingly threatened by human activities and the impact of climate change. In this study, the water quality of the Haraz, Tajan, and Cheshmeh Kileh Rivers in Mazandaran Province was evaluated using three widely recognized and reliable water quality indices. Methods: Physicochemical data obtained from samples collected at specified stations during ۲۰۲۱ and ۲۰۲۳ were analyzed. The evaluated parameters included dissolved oxygen, biochemical oxygen demand, pH, turbidity, nitrate, phosphate, temperature, total coliforms, and total dissolved solids. Results: The results demonstrated that the National Sanitation Foundation Water Quality Index (NSFWQI) and Iranian Water Quality Index (IRWQI) generally classified the water quality of the Haraz, Tajan, and Cheshmeh Kileh Rivers as Moderate to Good, whereas the British Columbia Water Quality Index (BCWQI) categorized several stations as falling within the Poor category. This outcome is consistent with findings from national and international studies, which indicate that the BCWQI tends to be more stringent and sensitive to deviations from established water quality standards. Conclusion: A comparison of the present study with domestic and international research validates the reliability of the results and confirms that the observed differences among the indices (especially the greater sensitivity of BCWQI) are fully consistent with global observations. These similarities indicate that the use of the Water Quality Index (WQI) in surface water studies can well reflect spatial and temporal changes in river water quality in humid regions with a temperate climate, such as Mazandaran Province.

کلیدواژه ها:

Physicochemical water quality parameters ، Environmental monitoring of rivers ، Northern Iran water quality monitoring ، WQI