Latvia has an abundant network of rivers, contributing to the visual beauty and the economy of the country. The largest river is the Daugava, which has been an important route for several thousand years. It has been used by local tribes as well as by Vikings, Russians, and other Europeans for trade, war, and conquest. With a total length of 1,020 kilometers, the Daugava (or Zapadnaya Dvina in its upper reaches) originates in the Valday Hills in Russia's Tver' Oblast, meanders through northern Belarus, and then winds through Latvia for 370 kilometers before emptying into the Gulf of Riga. It is about 200 meters wide when it enters Latvia, increasing to between 650 and 750 meters at Riga and to 1.5 kilometers at its mouth.

The river carries an average annual flow of twenty-one cubic kilometers. Its total descent within Latvia of ninety-eight meters has made it an attractive source of hydroelectric power production. The first hydroelectric station, at Kegums, was built during Latvia's independence period. The second dam, at Plavinas, aroused an unusual wave of protest in 1958. Most Latvians opposed the flooding of historical sites and a particularly scenic gorge with rare plants and natural features, such as the Staburags, a cliff comparable in cultural significance to the Lorelei in Germany. The construction of the dam was endorsed in 1959, however, after the purge of relatively liberal and nationally oriented leaders under Berklavs and their replacement by Moscow-oriented, ideologically conservative cadres led by Pelse. The third dam, just above Riga, did not provoke much protest because of the seeming hopelessness of the cause. The proposed fourth dam, at the town of Daugavpils on the Daugava River, became the rallying point for protest in 1986-87 by hundreds of thousands of Latvians. This dam was not constructed, in spite of the vast expenditures already poured into the project.

Smaller rivers include the Lielupe, in central Latvia, with an average annual flow of 3.6 cubic kilometers; the Venta, in the west, with 2.9 cubic kilometers; the Gauja, in the northeast, with 2.5 cubic kilometers; and the Aiviekste, in the east, with 2.1 cubic kilometers. Very little hydroelectric power is generated by their waters, although planners are now thinking of reactivating some of the abandoned older dams and turbines. The Gauja is one of Latvia's most attractive, relatively clean rivers and has an adjoining large national park along both of its banks as one of its notable features. Its cold waters attract trout and salmon, and its sandstone cliff and forest setting are increasingly a magnet for tourists interested in the environment.

More than 60 percent of the annual water volume of Latvia's six largest rivers comes from neighboring countries, mainly from Belarus and Lithuania. These adjoining resources create obvious needs for cooperation, especially in pollution control. The dangers from a lack of cooperation were brought home to Latvians in November 1990, when a polymer complex in Navapolatsk, Belarus, accidentally spilled 128 tons of cyanide derivatives into the Daugava River with no warning to downstream users in Latvia. Only the presence of numerous dead fish alerted Latvian inhabitants to the danger.