Rio Grande do Sul, state (1996 pop. 9,445,000), 108,951 sq mi (282,183 sq km), S Brazil, bordering on Argentina and Uruguay and on the Atlantic Ocean. Pôrto Alegre is the capital.

Rio Grande do Norte, state (1996 pop. 2,415,567), 20,469 sq mi (53,015 sq km), NE Brazil, on the Atlantic Ocean. Natal is the capital.

Rio Grande, city (1991 pop. 172,422), Rio Grande do Sul state, S Brazil, on the Rio Grande River at the outlet of the Lagoa dos Patos (a tidal lagoon) to the Atlantic Ocean. It is an important outport for the city of Pôrto Alegre on the northern end of the lagoon. Rio Grande has oil refineries and factories producing foodstuffs, leather, and tires. The city was founded in 1737.

Rio Grande, name of several rivers of Brazil. The largest rises in S Minas Gerais state, SE Brazil, and flows c.650 mi (1,050 km) NW to the Paranaíba River, with which it forms the Paraná River. Its lower course forms part of São Paulo's northern boundary. The huge Furnas Dam with its reservoir near Passos, Minas Gerais, serves the industrial heart of Brazil with hydroelectricity.

Rio Grande, river, c.1,885 mi (3,000 km) long, rising in SW Colo. in the San Juan Mts. and flowing south through the middle of N.Mex., past Albuquerque, then coursing generally southeast as the border between Texas and Mexico, making a big bend (see Big Bend National Park), and eventually emptying into the Gulf of Mexico at Brownsville, Tex., and Matamoros, Mex. Other paired towns along the river are Laredo, Tex., and Nuevo Laredo, Mex. and El Paso, Tex., and Juárez, Mex. The river, known in Mexico as Río Bravo del Norte, is unnavigable except near its mouth, but is now often reduced to a trickle there by drought and the drawing off of water upstream.

The Rio Grande is an important source of internationally regulated irrigation, a use it has long been put to. Pueblos were thriving on its banks N of Las Cruces, N.Mex., and the Native Americans were practicing irrigation of the arid country, when Spanish explorer Francisco Vásquez de Coronado arrived (1540). Today, dams on the Rio Grande are used for irrigation, flood control, and regulation of the river flow. Elephant Butte Dam (completed 1916) and Caballo Dam (completed 1938) in New Mexico create reservoirs that serve large areas. Further downstream N of Del Rio, Tex., is the Amistad Dam (completed 1969); it is 6 mi (9.7 km) long and impounds a huge reservoir; Amistad National Recreation Area is there. Below Laredo are Falcon Dam (completed 1954) and its large reservoir. Near the mouth of the Rio Grande is the irrigation-dependent citrus-fruit and truck-farm region commonly called the Rio Grande Valley and developed principally in the 1920s. An agreement between the United States and Mexico in 1944 provided for future distribution of the river's water, but in drought years the amount reaching the United States is often less than what is called for under the treaty.

Shifts in the river's channel have led to border disputes between the United States and Mexico. Parts of its bed have been stabilized by canalization, and an international border commission mediates disputes. The 114-year controversy over the location of the border at El Paso was finally settled in 1968 when the water of the Rio Grande was diverted into a concrete channel. A 191-mi (307-km) section of the river on the American shore below Big Bend National Park is protected as the Rio Grande Wild and Scenic River (see National Parks and Monuments, table).

in Mexico Río Bravo

River, North America. One of the longest rivers of North America, it flows 1,900 mi (3,000 km) from its sources in the Rocky Mountains of southwestern Colorado, U.S., to the Gulf of Mexico. It rises high in the San Juan Mountains and flows generally south, passing southeast and forming the entire border between Texas and Mexico. The earliest European settlements were along the lower course of the river in the 16th century, but many of the Pueblo Indian settlements of New Mexico date from before the Spanish conquest. During the Spanish period, the middle and upper portions were called the Río del Norte, and the lower course was called the Río Bravo. It is a major source of irrigation. At the U.S.-Mexican border, it defines the edge of Big Bend National Park, Texas.

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