evaluation of karun river water quality scenarios using simulation model results

karun river is the largest and most watery river in iran. this river is the longest river which located just inside iran and ahvaz metropolis drinking water supplied from karun river as well (fa.alalam.ir). karun river as the main source of water treatment plants in ahvaz, like most surface waters affected by various contaminants which caused changes in water quality of the river (www.aww.co.ir). causes such as constructing several dams at upstream river, withdrawal of water from the upstream to the needs of other regions of iran, exposure of various industries along the river and discharge of industrial and urban sewage into the river, seen that today this river is deteriorating rapidly, qua today is the depth of river reach to 1 m with a high concentration of pollutants (www.tasnimnews.com). in this study, considering the quality parameters, by using the qual2k model and with regard to water quality standards of defined classification, we defined various scenarios. then two parameters, bod and do were chosen as indicator parameters for assessing these scenarios. model was calibrated to data from spring 2012 and validation was performed by winter and spring 2013. then the model was used to take management decisions for critical situation. the results showed that by changing in location of entry pollutant in the river we achieved water environmental goals. this scenario is also useful for future that flow of river reduced.