The hydroecological characteristics of current state of the Zaporizhzhia (Dnipro) reservoir and its tributaries

Purpose: to determine the hydroecological condition of the different areas of the Zaporizhzhia (Dnipro) reservoir and its tributaries (Samara River, Konoplyanka River), which are under technogenic pressure. Methodology: classical methods of determining hydrochemical indicators (pH, dissolved oxygen, carbon dioxide, permanganate oxidizability, anions and cations of organic and inorganic compounds) and microbiological parameters (total count of microorganisms and count of saprophytes) were used during the study. The content of heavy metals was determined by atomic absorption spectrophotometry. Findings: The study of the current hydroecological state of the Zaporizhzhia (Dnipro) reservoir in the summer period showed that, according to most parameters, the water quality did not exceed the MAC (maximum allowable concentration) for fish farming. The exception was the reduced oxygen dissolved concentration (by 10-25%) in almost all areas of the reservoir, and the high mineralization of water in the Samara Bay (2 MAC), due to the discharge of highly mineralized waters of the Samara River. In the long-term aspect, there is an increase in the total mineralization of the Samara River (4 MAC, which is under the influence of the discharge mine waters of the coal mining industry of Western Donbas. The analysis of the content of heavy metals in the reservoir indicated an increase in the concentration of copper - from 13 MAC in the Samara Bay to 21 MAC in the lower part of the reservoir. The Samara River was characterized by a high content of cadmium (1.5 MAC), copper (13 MAC), and nickel (2.3 MAC). Indicators of the ecological state of the Konoplyanka River had significant differences in its different areas: in the upper reaches of the river, where the economic and domestic effluents of the city of Kamianske and the tailings storage facilities for radioactive waste are located, water did not meet the MAC for oxygen content, carbon dioxide, nitrites, nitrates, mineral ions (Ca2+, Mg2+, Cl’, SO4-2), general mineralization and the count of saprophytic microorganisms; at the mouth of the river, exceeding the MAC for nitrate content and saprophytic microflora was recorded. Originality: data on the hydroecological state of the Zaporizhzhia (Dnipro) reservoir and its tributaries in the conditions of the war have been obtained. Practical value: the results of the conducted study can be used to develop a strategic program for the restoration of the ecosystem of the Dnipro reservoirs in the post-war period. Key words: Zaporizhzhia (Dnipro) reservoir, tributaries, hydrochemical parameters, count of microorganisms, heavy metals.