Dissolved Oxygen Content in the Reservoirs of the Volga River

Abstract

Dissolved oxygen content determined by the Winkler method and water saturation by oxygen were studied in the reservoirs of the Volga River in summer 2015 and 2016 in the surface and near bottom layers of water. In the reservoirs of the upper reaches of the Volga River, including the Uglich and Ivankovo reservoirs, oxygen content in the water rather often was lower than its limiting permissible concentration for water bodies used for fishery. Significant oxygen deficiency was observed in hypolimnion at all stations of the Uglich Reservoir. Rather often (in 10-45% of cases) its content was lower than 2 mg/L, whereas in the Ivankovo Reservoir - in 75% of cases. In the reservoirs of the middle and lower reaches of the Volga River, dissolved oxygen content was within the normal range favorable to the development of hydrobionts, which was conditioned by intensive wind stirring and high current velocity, especially in the lower reaches of the river. During the period of investigations in the surface layer of water of the lake section of the Gorky Reservoir, dissolved oxygen content was higher than that in its river section. In the other studied reservoirs, the distribution of dissolved oxygen over their area of water was rather uniform.