Modern hydrological characteristics of the Kuibyshev reservoir as a basis for the development of water bioresources

THE PURPOSE. Consider the indicators of the operation mode of the Kuibyshev reservoir over the past 15 years, affecting the state of the fish stock; identify the main trends in changes in water volumes in the reservoir due to climate change, the features of the level regime for the ecological solution of the problem of preserving aquatic biological resources.METHODS. A comparative analysis of our own research and literature data on the hydrological characteristics of the Kuibyshev reservoir, the temperature regime of the region and the state of the ichthyofauna was carried out. In this work, to analyze the current state of the hydrological regime, data provided by the Verkhniy Byef gauging station of the branch of JSC RusHydro - Zhigulevskaya HPP and the State Committee of the Republic of Tatarstan for Biological Resources were used.RESULTS. It is shown that the average water level in the Kuibyshev reservoir for the last period ranged from 50.34 to 52.31 m at NHL - 53.00 m BS, DVL - 45.5 m. Based on the totality of characteristics in terms of average water levels and inflows, 2010, 2011, 2021 can be attributed to low-water years, 2007-2009, 2012-2020 to years with average water content, and there were no high-water years during this period.The analysis of the dynamics of changes in the maximum and minimum water levels was carried out and changes were identified: the minimum recorded water level (48.16 m) was noted in January (2011), at the end of the 20th century, the minimum levels were recorded in March - April and they were lower by 1-1, 5 m in summer drawdown and 2.5 - 3.5 m in winter, the level rise occurs in April, while earlier it was in May. The duration of the high-water period (about 53 m) increased to 4 months. The minimum volume in the reservoir was recorded in the winter period of 2010-2011 - 36.14 km3, the maximum volume is 57.66 km3 in the winter period of 2019-2020. Maximum water discharges are carried out mainly in the second half of April and early May. Minimum discharges are carried out in different periods.It is shown that the number of days with an air temperature above 15°C, which characterizes the fishery zone, varies in different years of the last period from 71 days (2017) to 133 days (2020).CONCLUSION. A relative increase in temperature was noted as the most important environmental factor for the development of aquatic bioresources; currently, the process of accelerating eutrophication of shallow areas of the Kuibyshev reservoir is observed. The regular death of fish in different parts of the reservoir, combined with factors such as low water levels and high temperatures, creates the preconditions for “local catastrophes” at the level of ichthyocenoses, the area of “local catastrophes” is expanding due to climate change. The mortality of fish is a mechanism for the release of the ecosystem from excess organic matter, and the mortality of a small particle indirectly indicates a high abundance of low-value and weedy fish, the number of which must be reduced.