Water quality index as a simple indicator of watersheds pollution in southwestern part of Iran

The K arun R iver is the most important watershed in the southwestern region of I ran. Water quality parameters were sampled from O ctober 2006 through J uly 2007 at three sites along a 4 km gradient, covering both the wet and the dry season. Surface water was collected at three different stations per site (close to the banks and in the middle of the river) and analysed for 14 parameters and heavy metals. The values of 1300, 196.8 and 4042.9 ppm for chemical oxygen demand, biochemical oxygen demand and chloride, respectively, were higher than the standards limits. water quality index ( WQI ) values were very useful for the classification of the waters monitored. The averaged WQI was low (47%), and quality declined significantly during the dry season [analysis of variance ( ANOVA , P < 0.05)]. The annual WQI values of 54.60, 40.29 and 45.71 from sites 1, 2 and 3 correspond to medium, bad and bad water qualities, respectively.