To design and implement monitoring programs for Tajan river water, factors such as frequency of sampling, analytical methods, site selection and criteria for water use area, were defined accordingly. A monitoring station was selected upstream of the river, inside Sari City and downstream close to Caspian Sea (delta). Samples were collected in 500 mL sterilized bottles on a monthly basis for physical, chemical and microbiological analysis. Sampling and analyses were carried out in accordance with standard methods. The results of water quality at different sampling locations show a moderate range of 7.6-8.2 pH. Total dissolved solids (TDS) are in the range of 350-1100 mg/L and at Delta up to 10800 mg/L. Maximum values for BOD and COD are 18 and 53 mg/L; maximum value of nitrates is 2.6 mg/L. The results show that the river quality is in moderate range. However, the presence of faecal-coliforms is indicative of the presence of domestic waste in the river water.
