Chlorophyll Content as an Indicator of the Modern (2015–2016) Trophic State of Volga River Reservoirs

Data on the chlorophyll a (Chl a ) content in water of the Volga River reservoirs sampled at 64–73 sampling stations in the summer period of 2015 and 2016, analyzed using the standard spectrophotometric method, are presented. Chl a content varied from a minimum of 0.9–3.0 to a maximum of 7.6–32.1 μg/L in June 2016, from 2.1–15.5 to 9.4–86 μg/L in August 2015, and from 1.1–6.7 to 15.1–62.7 μg/L in August 2016. A local increase in Chl a occurred in the near-dam areas of the reservoirs, as well as downstream of the confluence with tributaries. The highest Chl a concentrations were constantly recorded in the highly eutrophic Shoshinskii Reach in the Ivankovo Reservoir and at the Oka River mouth in the Cheboksary Reservoir. The average values of Chl a concentrations make it possible to classify the Ivankovo, Uglich, Rybinsk, and Cheboksary reservoirs as eutrophic; the Gorky and Kuibyshev reservoirs as moderately eutrophic; and the Saratov and Volgograd reservoirs as mesotrophic.