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The aim of the analysis was to compare physicochemical parameters and chemical composition of two groups of artificial reservoirs, mountain and lowland ones, characterised by different parameters and functions. Three mountain artificial reservoirs (Klimkówka, Dobczyce, Czorsztyn) located in the Upper Vistula basin (Carpathian Mountains in Poland) and three lowland reservoirs (Ivankovo, Verhnevolzhskoye, Vyshnevolotzkoye) located in the Upper Volga basin (Eastern European Lowland in Russia) were selected for the study. Data for the summer season in 2009-2013 were used in the analysis. Mountain reservoirs display high water concentrations of sulphates, chlorides and biogenic nitrates, and lower concentrations of ammonium and oxygen indicator in relation to lowland reservoirs. Similar concentrations of phosphates were noticed in both the mountain and the lowland reservoirs. The hydrochemical differentiation between the individual mountain reservoirs was small, and statistically significant differences only occurred for SEC. Greater differentiation of the hydrochemical parameters was found among the lowland reservoirs. Statistically significant differences were demonstrated with regard to SEC, Cl- and NO3-.

Conditions of formation, distribution, and accumulation of bottom sediments and chemical pollutants in the Ivankovo Reservoir and their impact on water quality have been considered on the basis of the long-term observation data. According to the monitoring results, it has been stated that current bottom sediments are composed of coarse-grained alluvium (38%), fine-dispersed sediments (38%), and soil (15%). Sediment accumulation decreased two folds under Transformation of the suspended matter balances caused two times decrease of sediment accumulation resulted in the increase of the amount of suspended solids saturated with pollutants. Considerable changes occurred in deposited macrophytes; their proportion increased from 16.7 to 26 – 28%, swamped soils constituted 14% of the reservoir area. The decrease in the rate of sedimentation and changes in the area of the reservoir caused a two-fold decrease in the rate of nutrient accumulation. Re-suspension of sediments and trans-sedimentation causing a secondary pollution of water with nutrients and toxic elements occur in the presence of vast shallow zones up to 3 m depth constituting about 53% of all area of the reservoir. As a result, the water quality is of a fluctuating character. This is especially distinctly manifested during the flood period when the maximum input of pollutants of natural and anthropogenic origin from residential territories, with atmospheric precipitation, ground and river runoff is observed upon filling the reservoir to the designed level and intensive hydrodynamic pressure. The results of hydrochemical surveys performed in 2012 and in the following years confirmed insignificant changes in physical and chemical parameters of elements of the ecosystem in the Ivankovo Reservoir. Since the construction of the reservoir permanganate oxidation, total iron, manganese, water mineralization and the content of the main ions are stable and depend on hydrometeorological conditions of the year. Interannual and seasonal dynamics of these parameters is observed. Despite the spatial and temporal variations, bottom sediments are the most conservative components in the environment.