Quality assessment of Zarrinehroud River Using Qual2k Simulation Model

Background& objectives: Zarrinehrud River is one of the most important permanent and water-rich rivers in West Azerbaijan province located in the catchment area of Lake Urmia. In this study, to evaluate the quality of the Zarrinehrud River, with a length of 57.5 kilometers from the outlet of Noroozlou to the drainage dam to the Lake Urmia, QUAL2K computer simulation model was used. Methods: The selected parameters of the model included: flow, dissolved oxygen (DO) and biochemically required oxygen. The selected time for the simulation was May 2016. Model calibration was performed by determining the oxidation coefficients of carbonaceous materials and the re-aeration coefficient of the river, using the mean square root of error (RMSE) method Results: The results show that the water quality of the river downstream of the Noruzlu regulatory dam has caused significant changes in the quality parameters of the river due to receiving wastewater from slaughterhouses, sugar factories, urban, rural and agricultural drains. Conclusion: Due to the high self-purification capacity of the river, the amount of dissolved oxygen is appropriate and the amount of BOD has reached an acceptable level despite a sudden increase. In terms of matching the observational data with the output diagram of the model, there was a good fit in other parameters except flow rate. In the case of non-compliance of the observed flow data with the simulation diagram, it may be due to unauthorized withdrawals from the river for agricultural purposes.