The Soviet Union's water resources are both scarce and abundant. With about 3 million rivers and approximately 4 million inland bodies of water, the Soviet Union holds the largest fresh, surface-water resources of any country. Unfortunately, most of these resources (84 percent), as with so much of the Soviet resource base, are at a great distance from consumers; they flow through sparsely populated territory and into the Arctic and Pacific oceans. In contrast, areas with the highest concentrations of population, and therefore the highest demand for water supplies, tend to have the warmest climates and highest rates of evaporation. The result is barely adequate (or in some cases inadequate) water resources where they are needed most.

Nonetheless, as in many other countries, the earliest settlements sprang up on the rivers, and that is where the majority of the urban population prefers to live. The Volga, Europe's longest river, is by far the Soviet Union's most important commercial waterway. Three of the country's twenty-three cities with more than 1 million inhabitants are located on its banks: Gor'kiy, Kazan', and Kuybyshev.

The European part of the Soviet Union has extensive, highly developed, and heavily used water resources, among them the key hydrosystems of the Volga, Kama, Dnepr, Dnestr, and Don rivers. As is the case with fuels, however, the greatest water resources are found east of the Urals, deep in Siberia. Of the sixty-three rivers in the Soviet Union longer than 1,000 kilometers, forty are east of the Urals, including the four mighty rivers that drain Siberia as they flow northward to the Arctic Ocean: the Irtysh, Ob', Yenisey, and Lena rivers. The Amur River forms part of the winding and sometimes tense boundary between the Soviet Union and China. Taming and exploiting the hydroelectric potential of these systems has been a monumental and highly publicized national project. Some of the world's largest hydroelectric stations operate on these rivers. Hundreds of smaller hydroelectric power plants and associated reservoirs have also been constructed on the rivers. Thousands of kilometers of canals link river and lake systems and provide essential sources of irrigation for farmland.

The Soviet Union's 4 million inland bodies of water are chiefly a legacy of extensive glaciation. Most prominent among them are the Caspian Sea, the world's largest inland sea, and Lake Baykal, the world's deepest and most capacious freshwater lake. Lake Baykal alone holds 85 percent of the freshwater resources of the lakes in the Soviet Union and 20 percent of the world's total. Other water resources include swampland, a sizable portion of territory (10 percent), and glaciers in the northern areas.