Water quality monitoring has an important application in a sustainable management of river ecosystems. This is due to the fact that temporal and spatial quality of river are influenced by human activity and land use in adjacent areas. Overall evaluation of water quality is not an easy task, as there are so many different standards in use. Water quality indices (WQI) are considered as a simple and understandable tools for managers and decision maker, in determining water quality and potential for consumption. Babolrud river is one of the important rivers in northern part of Iran , and is a crucial source of water for aquacultural and agricultural purposes. However, industrial and urban development in recent years has caused a major degradation of the river water quality. In order to study the water quality of Babolrud river, monthly sampling were carried out from five stations, from September 2006 till August 2007. The water samples were analyzed to determine temperature, pH, Ec, TDS,TSS, DO, COD, BOD 5 , NO - 3 , PO - 4 , turbidity and total and fecal coliforms. Results showed a significant difference (P 0.05) between the mean values of DO, BOD 5 and COD at different month and stations. The values of these factors improved during cold seasons due to the increase in water flow. The result also indicated that the stations located downstream are more polluted than upstream one. Although, the values of turbidity, pH, TSS and TDS showed no significant differences between the stations, but it was significant (p 0.05) at different time of the year. According to indices used for water quality assessment, Babolrud river is ltr"
