Qualification Zoning of the Dohezar River according to NSFWQI and Using GIS

Background and Using water quality indices is one of the methods for checking river’s water quality. NSFWQI, is the most widely used among water quality indices. This study aimed to evaluate the water quality in Dohezar river, Tonekabon, using NSFWQI. In this study, sampling was performed during 6 months 3 month with low level of water and 3 months with high level of water) in 6 selected stations along the river. Quality parameters included temperature, dissolved oxygen, biological oxygen demand, PH, nitrate, phosphate, total dissolved solids, turbidity, opacity, and excremental coliform. Data was analysed applying NSFWQI and finally river route was zoned in different sections using GIS. Compared to drinking water and surface water quality standards, apart from opacity parameter, which was not in permitted range in up-stream and mid-stream, the other measured parameters in both low and high-level of water periods in all stations, were in acceptable range. According to the results obtained from NFSWQI in Dohezar river, on low-level of water periods, water quality in up-stream, mid-stream, and down-stream were in acceptable range (71- 90). In high-level of water periods, water quality was in good range just in up-stream butmid-stream and down-stream water qualities were in average range (51-70). Due to the river’s high flow and limited influx of contaminants, most contaminators were associated with aquaculture farms.