Negro River

I

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.

II

or Guainía River

River, northwestern South America.

A major tributary of the Amazon River, it rises in the rainforest of eastern Colombia, where it is known as the Guainía, and forms a section of the border between Colombia and Venezuela. It crosses Brazil and joins the Amazon at Manaus. It is about 1,400 mi (2,250 km) long and is a major transport artery. Its name comes from its jet-black colour, which is caused by the decomposition of organic matter and its low silt content.

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▪ river, Argentina

Spanish  Río Negro,  

      river, southern Argentina, whose major headstreams, the Neuquén and the Limay, rise in the Andes Mountains near the Chilean border. At Neuquén city they meet to form the Negro, which flows generally east-southeastward across northern Patagonia and empties into the Atlantic Ocean southeast of Viedma and Carmen de Patagones. The length of the Negro is about 400 miles (640 km; 700 miles [1,125 km], including the Neuquén), but only the lower 250 miles (400 km) are navigable. The waters of the Negro are used for hydroelectricity and for irrigation of grains and fruit, including wine grapes and apples for export to Europe.

▪ river, South America

Portuguese  Rio Negro,  Spanish  Río Negro,  

 major tributary of the Amazon (Amazon River). It originates in several headstreams, including the Vaupés (Mapés) and the Guainía (Guainía River), which rise in the rain forest of eastern Colombia. The Guainía flows east and then arches northeast and southeast, forming the Colombian–Venezuelan border. Below its junction near San Carlos de Río Negro with the Brazo Casiquiare, a natural waterway that brings water from the Orinoco River in Venezuela, the river acquires the name Negro and enters Brazil. The Negro meanders generally east-southeastward, picking up the Branco River (q.v.) and other tributaries, to Manaus. There it joins the Solimões River (q.v.) to form the Amazon. Its length is about 1,400 mi (2,253 km), of which 850 mi are in Brazil. It is navigable for about 450 mi above its mouth.

      Although settlement along its banks is sparse, the river is a major transportation artery. The clear, jet-black colour of the Negro's water, whence comes its name, is caused by the decomposition of organic matter in marginal swamps and its low silt content; its colour contrasts dramatically with the yellowish, silt-laden waters of the Branco and with the Amazon.

▪ river, Uruguay

Spanish  Río Negro , Portuguese  Rio Negro 

      river in Uruguay, rising in the southern highlands of Brazil just east of Bagé. The Negro flows southwestward into Uruguay, where it is dammed near Paso de los Toros to create the Rincón del Bonete Reservoir (also called the Gabriel Terra Reservoir or the Rio Negro Reservoir), the largest artificial lake in South America (4,000 square miles [10,360 square km]). Downstream are two dams, the Baygorria (Rincón de Baygorria) and Palmar, which are a major source of hydroelectric power for Uruguay. Below the dams the river meanders westward past Mercedes to join the Uruguay River at Soriano. The confluence is marked by several islands, the largest of which are Vizcaíno, Lobos, and Infante. Although the Negro is approximately 500 miles (800 km) long, it is navigable for only 45 miles (72 km) upstream from its mouth.

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