Influence of the mass development of cyanobacteria on the formation of the water quality of the Kuibyshev reservoir (problem and solutions)

The process of mass development of cyanobacteria has a negative impact on the ecological state and water quality of the reservoirs of the Volga-Kama cascade, which are used for drinking water supply, fisheries and recreation. The main goal of the research is to assess the impact of the mass development of cyanobacteria on the formation of water quality using the example of the Kuibyshev reservoir in the context of global warming. Comprehensive observations were carried out in the period 2001-2021. on the largest in Europe Kuibyshev reservoir with seasonal, weekly and daily regime of water line regulation. The research results show that during the period of “water bloom” organic water pollution increases. So permanganate oxidation in summer exceeds the permissible value by 1.5-2.0 times, which creates problems in providing the population with high-quality drinking water. The mass development of cyanobacteria disrupts the oxygen regime of the reservoir. The seasonal variability of the dissolved oxygen concentration includes four periods, which differ in the different directions of the processes of formation of the oxygen regime. Within the year, two minima of the dissolved oxygen content are observed: winter and summer. In the summer minimum, the concentration of dissolved oxygen decreases to critical values, and is 4-5 mg/dm3. The mass development of cyanobacteria has a significant influence on the formation of the summer oxygen minimum. As a result of photosynthetic aeration, a thin surface layer of water supersaturated with oxygen is formed, which disrupts the process of oxygen absorption from the atmosphere in a significant part of the reservoir water area. Under conditions of growing nutrient load and global climate warming, the intensity and scale of the process of mass development of cyanobacteria in the Kuibyshev reservoir will only increase, which will lead to a further increase in oxygen deficiency, deterioration of water quality and the emergence of water use risks.