Investigation of Daily Waste Load Allocation in Zarrineh-Rud River for Environmental Management of Cold-Water Fish Species

A critical aspect of qualitative management of water resources is the optimal waste load allocation in a river system. Zarrineh Rud is one of the crucial, permanent, waterrich rivers in West Azerbaijan province in the northwest of Iran and the Urmia lake basin. The present study investigates the effects of daily waste load on environmental management of cold-water fish species in a portion of Zarrineh Rud with a length of 57.5 km using the QUAL2K simulation model. The selective parameters of the model were flow rate, dissolved oxygen (DO), biochemical oxygen demand (BOD). Simulations were conducted for May 2019. The model was calibrated by determining the oxidation coefficient of carbonic materials and the reaeration coefficient of the river, based on the root-mean-square-error (RMSE) measure. To determine the susceptible and critical points in Zarrineh Rud, the dissolved oxygen (DO) was considered the most critical indicator based on standards associated with cold-water fish farming and maintaining the aquatic life in the river ecosystem. Results showed that the concentration of dissolved oxygen in the river is variable between 7-8 mg/L, which exceeds the maximum standard value required for aquatic life. The output data of the simulation model revealed that the maximum allowable value of dissolved oxygen deficit is 2 mg/L based on cold-water fish species standard and 1.35 mg/L based on aquatic life preservation standard. The station S5 at the river downstream with 3.53 mg/L dissolved oxygen deficit was the most critical point for cold-water fish farming, and the 26th kilometer of the river with a dissolved oxygen deficit of 2.05mg/L was the most critical point for maintaining the aquatic life; therefore, some scenario must be developed for waste load reduction at this station.