Study on Water Quality of Karoun River (Ahvaz region) Using Water Quality Index

Karoun River is one of the most important water ways and longest rivers of Iran. Because of agricultural farms, industrial units and cities in its vicinity, the Karoun River has a strategical position. Hence, its water quality monitoring is essential due to many point and non point sources of pollution. This study was carried out to evaluate Karoun River’s water quality in Ahvaz region. For water quality data's analysis in various stations, index of water quality NSF (National Sanitation Foundation) software from Wilkes University is used. Therefore Dissolved Oxygen, fecal coliform, pH, BOD5, Nitrate, Phosphate, Temperature, Turbidity and Total solids were determined on monthly basis. The monthly WQI in studied stations fluctuates from 57 to 70 that fall within medium category. Water quality index from first to last station gradually decreased. The results of WQINSF for river bank water quality computation during 1 year sampling period show that Koot-Abdollah station (lower part of the river) has the worst situation with yearly index of 62.5 and Kian-Abad station (upper section of the river) has the best quality amongst studied stations (65.25). Because of river bed and self purification, seasonal change has insignificant effects on water quality in Pol-e-Siah station. Water quality (in spring) because of the suitable conditions for growth of fecal coliforms and increased turbidity- has worst situation and in autumn season -because of the incensement of rain and decreasing of contaminations- has best situation.