São Francisco (souN frəsēshˈkŏ) [key], river, c.1,800 mi (2,900 km) long, rising in the Serra de Canastra, SW Minas Gerais state, Brazil, and flowing northeast, then southeast through the sertão region of E Brazil to the Atlantic Ocean. The river's flow varies with the season. The São Francisco, an ancient river that is embedded in the Brazilian Plateau, probably once entered the sea near Cape São Roque, northeast of its great bend. The near right-angle bend near Cabrobó is believed to be caused by stream piracy (see river). Paulo Afonso Falls (275 ft/84 m high), east of the great bend, blocks navigation into the interior; a railroad circumvents the falls. The river is navigable along c.900 mi (1,450 km) of its middle course. The São Francisco valley, linking Brazil's northeastern and southeastern regions, is the object of a large-scale river development and control scheme. The harnessing of Paulo Afonso Falls and the building of several dams have improved economic conditions in the potentially rich but drought-ridden and sparsely settled region.