Background: Unsustainable development of agriculture and aquaculture has reduced the water quality of rivers. The most important aim of this study is assessing of water quality in the Ghezel Özan basin in Zanjan province.
Method: 18 sites were selected based on standard criteria including land use, geology, biodiversity points, accessibility and standard distributions. Content of Dissolved Oxygen, Temperature, Turbidity and Electrical Conductivity were measured in-situ while number of Fecal Coliform, amount of BOD, COD, Phosphate, Nitrate, Nitrite, Ammonia, Sulfate and Chlorine were measured at laboratory.
Results: One-sample T.test showed a significant difference between the Coliform and its standard. Results have illustrated the remarkable impacts of agricultural and aquaculture activities on the river health. Also, among all quality parameters, Nitrate and Fecal Coliform show a significant difference in two regions, Tarom and Mahneshan. There is the best water quality in site 7 (upstream site) located far from human access. IRWQI index (Iranian water quality index for surface water) shows the best results because of more overlap with land-uses and the trend of variables.
Conclusion: Olive cultivation and unsustainable aquaculture development in Tarom and Mahneshan, respectively, are main reasons for decreasing of water quality. So, integrated water resources management, training local people, assessing environmental impacts and determining the ecological potential are highly recommended to improve the water quality of the studied river.