The lakes are natural reservoirs, representing a water-filled depression in the earth’s surface with a slow water exchange. By origin, the lakes of Ukraine are subdivided into river waters; failure, karst and sagging; residuals; glacial and landslide-blockage.
River lakes were formed in the erosional depressions of the floodplain, mainly in the oxbows – its ancient sites separated from the modern bed. Nutrition of river lakes is carried out mainly during the spring floods and during heavy rain showers. A significant number of lakes were in the floodplain of the Dnieper, but now they are flooded by the reservoirs of the Dnieper cascade. There are especially many lakes in the river basin of the forest zone (in Polesie), they are also found in the river valleys of the steppe and forest-steppe zones.
The hollow, karst and subsidence lakes occupy basins caused by leaching of soluble rocks (limestone, dolomite, chalk, gypsum, rock salt) and subsidence of the earth’s surface when leaching and removing small fractions from porous insoluble rocks. This type includes the deepest lakes of Ukraine – Svityaz (58.4 m, Western Bug basin) and Somine (56.9 m, Vizhivka basin – Pripyat tributary), located in Polesye.
Residual lakes are separated parts of sea bays, bays and near-estuary stretches of rivers. They were formed during sea transgressions (the advance of the sea), when the lower land areas and the estuarine sections of river valleys were flooded by its waters. During the subsequent retreat (lowering of the level) of the sea as a result of the wave-breaking activity, the flooded areas were separated from the sea by sand-shell rock-troughs.
Glacial lakes are the result of the activity of the continental (in Polesie) and mountain (in the Carpathians) glaciers.