Simulating the Water Quality of Qarasu River Using the QUAL2Kw Model

The aim of this research is evaluating the ability of the QUAL2Kw model in simulating the water quality parameters of Qarasu-River. The Qarasu-River is the main water supplier of the Sabalan reservoir dam which will be used for the drinking water consumption of Meshginshahr city in the near future. Therefore, it is very important to closely monitor the quality of the mentioned river for formulating policies and management plans.A section of 71.5 km was chosen as the study route. The field measurements were carried out in six stations in November 5, 2021 and 2022, for calibration and validation of the model. The value of the root mean square error (RMSE) for the parameters of flow rate, electrical conductivity, biological oxygen demand, nitrate, pH, dissolved oxygen, alkalinity and water temperature in the calibration stage were obtained 1.17, 505.8, 9.2, 0.22, 0.35, 109.85, 2.54 and in the validation stage were obtained 0.51, 212.88, 86.11, 10.79, 0.89, 5.11, 35/54 ,4/8 respectively. The results showed that the trend of changes in quality parameters along the studied route due to the discharge of wastewater treatment plant of Ardabil Industrial Town, discharge of wastewater from the Ardabil sewage treatment plant, the discharge of the effluent from the Samian Poultry Slaughterhouse, and the discharge of the effluent from the Ardabil Industrial Slaughterhouse into the Qarasu River were accompanied with extreme fluctuations. Nevertheless, due to the high power of self-purification of the river, the quality parameters of the river improved significantly in the downstream sections of the studied route. Also, two scenarios were defined with the conditions close to the reality. The results of the scenarios showed that the performance of the model is reasonable and the quality of the river water decreases with increasing the temperature of the point pollutant sources.