Dissolved oxygen concentration and eutrophication evaluation in Yamchi dam reservoir, Ardabil, Iran

Abstract

One of the essential issues in the quality management of water resources is the determination of the level of eutrophication and dissolved oxygen in dam reservoirs and other water bodies. It is possible to study changes in dissolved oxygen concentration using qualitative models. In this study, CE-QUAL-W2, a two-dimensional model of hydrodynamics and water quality capable of predicting the behavior of aquatic ecosystems, has been used to simulate dissolved oxygen concentration and eutrophication. As a case study, the water quality of the Yamchi dam reservoir, located in Ardabil Province, has been qualitatively investigated using the CE-QUAL-W2 model. Based on the geographical location of the Yamchi dam reservoir, it includes warm monomictic basins. According to the results, the dissolved oxygen concentration in the simulation period varied between 0 and 12 mg/L. In autumn and winter, this concentration was almost uniform at various depths. However, in summer, a sharp decrease in dissolved oxygen concentration, to less than 2 mg/L in the bottom layers, was observed, which is due to the presence of nutrients. Regarding eutrophication, the Yamchi dam reservoir is one of the eutrophic reservoirs, and practical strategies should be employed to improve these conditions. Recommended strategies include reducing the retention time of water in the reservoir, dewatering from the underlying layers during the thermal stratification period, and preventing the entry of agricultural drains into the inlet tributaries of the reservoir.