As might be expected for a country of such vast size, Russian water resources are enormous. Its territory contains some of the world's longest rivers and largest lakes.Hydrological potentials, however, are not equally distributed.While more than two million rivers flow through Russia, some areas remain parched during summer months when water is needed for agricultural purposes in particular.When lakes are included, the number of water bodies climbs to more than six million. Lakes and rivers are unevenly distributed because of the uneven distribution of precipitation. A majority of rain falls during a few short months while snow accumulates during the long winter season.
The largest amount of runoff occurs with spring snowmelt, which accounts for about two-thirds of the cumulative runoff. Water resources do not correspond to the distribution of human settlement need.Whereas the majority of Russians live west of the Ural Mountains, two-thirds of the available freshwater is located east of this dividing range. Additionally, in European Russia, decades of heavy industrialization and urbanization contributed to a decrease in water quality for individual and commercial use. Rivers discharge into several main bodies of water—the Arctic and Pacific oceans, and the Black, Caspian, and Baltic seas. In terms of volume, the largest recipient is the Arctic Ocean, into which flow waters of the Ob-Irtysh, Yenisey, and Lena rivers. Their watersheds cover most of Asiatic Russia.
Lakes are scattered throughout the country, but most are found in northern areas. A majority of the lakes were formed during the Pleistocene (ice age) period (1.8 million to 10,000 years ago) as continental glaciers advanced and retreated across the land. Both glacial scour and the pressure exerted on Earth's crust by the mass of glacial ice formed concave features on Earth's surface that became filled with water. Another kind of lake, a reservoir, is man-made; that is, those artificial bodies of water are created by humans to fulfill certain purposes such as providing water for irrigation.