Change of the ecological state of Yumaguzinskoe water reservoir after building

Phytoplankton and hydrochemical indicators of the Yumaguzinskoe water reservoir (South Urals) were studied. The chemical composition was sufficiently uniform and characterized by hydrocarbonate magnesium-calcium composition. Phytoplankton sampling and processing was carried out by standard methods. Development of the Yumaguzinskoe water reservoir is characterized by the moderate eutrophication. At present, the situation has improved and complied with our forecast of 0,95 % of the runoff. The authors identified 80 species and intraspecific taxa of algae and cyanobacteria at the highest species diversity of diatoms and green algae in 2012, 2014 and 2015. The dominant species were Chlorella vulgaris Beijer, Kirchniriella obesa (W. West) Schimidle, Synechocystis salina Sauv., Peridinum cinctum (O. Mull.) Ehr., Merismopedia minima G.Beck, Scenedesmus quandricanda (Turp.) Breb in size; Chlorella vulgaris Beijer, Chlamydomonas vulgaris Ehr., Peridinum cinctum (O. Mull.) Ehr., Euglena viridis Stein. in biomass. It has been a trend of increasing the number and biomass in 2006-2007 and a decrease in these indicators in 2012- 2015. Downstream water salinity gradually decreases. There is some dilution near the dam. The current state of the phytoplankton indicates the formation of oligotrophic conditions favorable for the formation of a satisfactory quality of water intakes located in the middle reaches of the Belaya river.