Modeling of Dissolved Oxygen in Ekbatan Reservoir Using CE-QUAL-W2 Model

This research, using the CE-QUAL-W2 hydrodynamic model, investigates and simulates the dissolved oxygen (DO) parameter in the Ekbatan dam reservoir under the influence of thermal stratification and temperature changes. Ekbatan Reservoir plays an important role in providing drinking and agriculture water in Hamedan city, so checking its water quality seems essential. The results show that the CE-QUAL-W2 model simulates well the temperature changes of the reservoir by considering the volume and geometry of the reservoir and meteorological parameters. Due to the fact that dissolved oxygen is affected by thermal stratification, the relationship between these two parameters has been investigated and the possibility of evaluating water quality through thermal stratification of the reservoir has been presented. The results show that thermal stratification in Ekbatan reservoir has periods of thermal stratification change and is complete in summer, while complete mixing occurs in autumn and early winter. These changes also affect the DO stratification in the reservoir. With a 68 percent increase in temperature, the DO concentration decreases by about 37.5 percent, and with a decrease in temperature, the DO concentration increases in the same proportion. In addition, the research results show that changes in air temperature have a significant effect on the concentration of DO in the reservoir. The change in temperature leads to a decrease in the density of water and a decrease in the solubility of oxygen in water, which in turn leads to a decrease in the concentration of DO in the reservoir water, and this issue is widely considered in environmental studies and water resources management.