Rio Grande

River of the USA and Mexico, rising in the Rocky Mountains in southern Colorado, it flows southeast, through New Mexico and Texas, to the Gulf of Mexico near Brownsville; length 3,050 km/1,900 mi. From El Paso, the river forms the US-Mexican border for the last 2,400 km/1,500 mi of its course. Insufficient water is carried for the demands of irrigation both sides of the border, and the Rio Grande is eventually reduced to a trickle in its lower reaches. Its rate of flow is subject to international agreements.

Irrigation dams have been constructed at Del Rio and south of Laredo in Texas. The Del Rio reservoir is called the Amistad Reservoir and is shared by both countries. The Laredo dam on the Texan border is known as the Falcon lake in the USA and Presa Falcón in Mexico. The Elephant Butte and Caballo reservoirs are in New Mexico. Excessive water consumption, pollution, and diversification of water away from the river channel, led to the river being listed as a ‘most endangered river’ in 2000.

Rio Grande (do Sul)

Seaport in southern Brazil, in the state of Rio Grande do Sul; population (1996) 178,256. Situated on the strait leading from the Atlantic Ocean to the Lagoa dos Patos, it has a large deep-water harbour and is one of Brazil's most important ports. Rio Grande is the main distribution centre for the southern part of the state and exports dried meat, wool, hides, and tobacco. There are cotton, wool, and jute factories, an oil refinery, and fisheries here.