ORINOCO RIVER

Spanish Ro Orinoco, major river of South America, rising on the western slopes of the Sierra Parima along the Venezuela-Brazil border and flowing in a giant arc through Venezuela for 1,700 miles (2,740 km) to enter the Atlantic Ocean near the island of Trinidad. The river flows mostly through Venezuela, except where it forms part of the border between Colombia and Venezuela. With its tributaries (including the Caron, Mavaca, Apura, Vichada, Meta, and Gurico rivers), the Orinoco is the northernmost of South America's four major river systems (the others are the Amazon, the ParanParaguayla Plata, and the So Francisco). Fed mainly by snow, its average annual rate of flow is about 1,060,000 cubic feet per second (30,000 cubic m per second), but because of seasonal variation in rainfall the flow fluctuates widely. The river carries immense amounts of sediments, and its vast delta is rapidly expanding into the Atlantic. Much of the river's drainage basin of 366,000 square miles (948,000 square km) consists of the broad grassland region of the Llanos; dense tropical rain forests are found on the eastern and southern highlands. The water fauna includes the carnivorous piranha; the laulao, a catfish that can attain a weight of over 200 pounds (90 kg); and the Orinoco crocodile, which is the longest of its kind in the world, reaching a length of more than 20 feet (6 m). The Macagua and the Guri dams on the Caron River are among the world's largest hydroelectric plants. The Guiana Highlands in the southeast have rich iron-ore and bauxite reserves. The river basin is largely inhabited by indigenous Indian groups. The Orinoco is navigable by large oceangoing vessels from its mouth to its confluence with the Caron (a distance of about 225 miles ). Ciudad Bolvar and Ciudad Guayana are the major port cities and centres of economic development along the river. The Northern Andes and the Orinoco River basin and its drainage network. Spanish Ro Orinoco, major river of South America that flows in a giant arc for some 1,700 miles (2,740 kilometres) from its source in the Guiana Highlands to its mouth on the Atlantic Ocean. Throughout most of its course it flows through Venezuela, except for a section that forms part of the frontier between Venezuela and Colombia. The name Orinoco is derived from Guarauno words meaning a place to paddlei.e., a navigable place. The Orinoco and its tributaries constitute the northernmost of South America's four major river systems. Bordered by the Andes Mountains to the west and the north, the Guiana Highlands to the east, and the Amazon watershed to the south, the river basin covers an area of about 366,000 square miles (948,000 square kilometres). It encompasses approximately four-fifths of Venezuela and one-fourth of Colombia. For most of its length, the Orinoco flows through impenetrable rain forest or through the vast grassland (savanna) region of the Llanos (Spanish: Plains), which occupies three-fifths of the Orinoco basin north of the Guaviare River and west of the lower Orinoco River and the Guiana Highlands. The savanna was given its name by the Spaniards in the 16th century and long has been used as a vast cattle range. Since the 1930s this region has been developing into one of the most industrialized areas of South America. Additional reading Detailed studies in Spanish of the physical and human geography of the Orinoco River basin include Rafael Gmez Picn, Orinoco, ro de libertad, 2nd rev. ed. (1978); and Francisco Tamayo, Los Llanos de Venezuela, 2nd ed. (1987). The most useful English-language description of the basin still is found in the essays by Alexander von Humboldt, Personal Narrative of Travels to the Equinoctial Regions of the New Continent, During the Years 17991804, trans. from French, 7 vol. (181429), available also in later editions. Specialized studies include Carl F. Nordin, Jr., and David Perez-Hernandez, Sand Waves, Bars, and Wind-Blown Sands of the Ro Orinoco, Venezuela and Colombia (1989); and Edwin D. McKee, Sedimentary Structures and Textures of the Ro Orinoco Channel Sands, Venezuela and Colombia (1989). Among the works on the people of the basin are Johannes Wilbert and Miguel Layrisse (eds.), Demographic and Biological Studies of the Warao Indians (1980); and Johannes Wilbert, Geography and Telluric Lore of the Orinoco Delta, Journal of Latin American Lore, 5(1):129150 (Summer 1979), also on the Warao Indians. The settlement of the Llanos is described in Jane M. Rausch, A Tropical Plains Frontier: The Llanos of Colombia, 15311831 (1984), and The Llanos Frontier in Colombian History, 18301930 (1993). The Editors of the Encyclopdia Britannica