Below its junction with the Ilim River the Angara is known also as the Upper Tunguska (Russian Verkhnyaya Tunguska). The Angara is navigable between Irkutsk and Bratsk; below Bratsk there are many rapids. At Bratsk there is a large dam with one of the world's largest hydroelectric power plants (ca. 4,500 MW); a smaller (660 MW) hydroelectric station is at Irkutsk. Two other dams span the river, making it one of the world's greatest sources of hydroelectric power.