Dynamics of Water Quality of the Tsimlyansk Reservoir over the 1979-2014 Period.

Analysis of many-year hydro/chemical information of the Rosgidroment state observation network that enables to assess the changes in the pollutants typical for the Tsimlyansk reservoir over the 1979–2014 period has been carried on the basis of a single methodological/methodical framework. The easily oxidizable organic substances dynamics (by BOD5) and organic substances (by COD), as well as changing of many-year season concentrations of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen and phosphates has been studied as they are the most active substances contributing to aquatic organisms vital functions in view of the cyanobacteriae-caused “blooming” typical for the Tsimlyansk reservoir. These biogenic elements’ concentration in water mostly depends on activity of the biological processes occurring within water bodies. It has been demonstrated that seasonal variations are characteristic for the organic matter, nitrogen and phosphorous mineral forms content in the Tsimlyansk reservoir water, and increase in their content can promote its euthrophication.Comparison of the observed data with the maximal permissible concentration values were used for the water quality assessment. An integrated assessment of the Tsimlyansk reservoir water quality dynamics has been accomplished at the most human affected ranges. Some trends of the Tsimlyansk reservoir monitoring system improvement in the conditions of the complicated hydrological situation caused by the 2010-2014 low-water period in the Don basin have been outlined: in particular, joint functioning of hydro/chemical and hydro/biological observation stations with hydrological stations. Bearing in mind that the in-reservoir processes of chemical substances transformation and redistribution are critical for the reservoir aquatic ecosystem functioning and sustainability it is very important to study exchange processes within the water-bottom sediments system.