River, central Uruguay.
It rises in the southern highlands of Brazil. Flowing southwest across Uruguay, it is dammed at the Rincón del Bonete Reservoir, the largest artificial lake in South America, with an area of roughly 4,000 sq mi (10,400 sq km). The river joins the Uruguay River at Soriano. Although it is 434 mi (698 km) long, it is navigable for only about 45 mi (70 km) upstream from its mouth.