TheOrinoco (Spanish pronunciation:[oɾiˈnoko]) is one of the longestrivers inSouth America at 2,140 km (1,330 mi). Itsdrainage basin, sometimes known as theOrinoquia, covers approximately 1,000,000 km2 (390,000 sq mi), with 65% of it inVenezuela and 35% inColombia. It is thefourth largest river in the world bydischarge volume of water (39,000 m3/s (1,400,000 cu ft/s) atdelta) due to the high precipitation throughout its catchment area (2,300millimetres perare [0.084 in/sq ft]). The Orinoco River and itstributaries are the major transportation system for eastern and interior Venezuela and theLlanos of Colombia. The environment and wildlife in the Orinoco's basin are extremely diverse.[2][6][7][8][9]
The river's name is derived from theWarao term for "a place to paddle", derived from the termsgüiri (paddle) andnoko (place) i.e. a navigable place.[10][11]
The mouth of the Orinoco River at theAtlantic Ocean was documented byChristopher Columbus on 1 August 1498, during histhird voyage. The Orinoco as well as its tributaries in the easternLlanos, such as theApure andMeta, were explored in the 16th century by German expeditions underAmbrosius Ehinger and his successors. In 1531, starting at the principal outlet in the delta, the Boca de Navios,Diego de Ordaz sailed up the river to the Meta.Antonio de Berrio sailed down theCasanare to the Meta, and then down the Orinoco and back toCoro. In 1595, after capturing de Berrio to obtain information while conductingan expedition to find the fabled city ofEl Dorado, the EnglishmanSir Walter Raleigh sailed down the river, reaching the savanna country.
From April to May 1800, the Prussian-bornAlexander von Humboldt and his companion,Aime Bonpland, explored stretches of the Orinoco, supported by indigenous helpers and guided by his interest to prove that South America's waterways formed an interconnected system from theAndes to theAmazon.[12] He reported on thepink river dolphins and later published extensively on the river's flora and fauna.[13]
The source of the Orinoco River, located at Cerro Delgado–Chalbaud (2º19’05” N, 63º21’42” W), at 1,047 m (3,435 ft) above sea level, was discovered in 1951 by a French-Venezuelan expedition that explored the upper Orinoco course to theSierra Parima near the border with Brazil, headed by Venezuelan army officer Frank Risquez Iribarren.[14][15]
In 1968, an expedition was set off byThe Geographical Journal andHovercraft fromManaus, Brazil. Aboard aSR.N6 hovercraft, the expedition members followed theRio Negro upstream to where it is joined by theCasiquiare canal, on the border between Colombia and Venezuela. After following the Casiquiare to the Orinoco River they hovered through perilous rapids of Maipures and Atures. The Orinoco was then traversed down to its mouths in theGulf of Paria and then to Port of Spain. The primary purpose of the expedition was filming for theBBC seriesThe World About Us episode "The Last Great Journey on Earth from Amazon to Orinoco by Hovercraft", which aired in 1970 and demonstrated the abilities of a hovercraft, thereby promoting sales of this British invention.
The first bridge across the Orinoco River, theAngostura Bridge atCiudad Bolívar, Venezuela, was completed in 1967.[16] The first powerline crossing of the Orinoco River was completed in 1981 for an 800kVTL single span of 1,200 m (3,900 ft) using two towers 110 m (360 ft) tall.[17] In 1992, an overhead power line crossing for two 400kV-circuits was completed west of Morocure (betweenCiudad Bolívar andCiudad Guayana). It had three towers, and the two spans measured 2,161 m (7,090 ft) and 2,537 m (8,323 ft), respectively.[17][18][19][20] In 2006, theOrinoquia Bridge was completed near Ciudad Guayana.[citation needed]
The course forms a wide ellipsoidal arc, surrounding theGuiana Shield; it is divided in four stretches of unequal length that very roughly correspond to the longitudinal zonation of a typical large river:
Upper Orinoco – 286 km (178 mi) long, from its headwaters to the Raudales de Guaharibos rapids, flows through mountainous landscape in a northwesterly direction
Middle Orinoco – 805 km (500 mi) long, divided into two sectors, the first of which ca. 515 km (320 mi) long has a general westward direction down to the confluence with theAtabapo andGuaviare rivers atSan Fernando de Atabapo; the second flows northward, for about 290 km (180 mi), along theColombia–Venezuela border, flanked on both sides by the westernmost granitic upwellings of the Guiana Shield which impede the development of a flood plain, to theAtures rapids near the confluence with theMeta River atPuerto Carreño
Lower Orinoco – 959 km (596 mi) long with a well-developedalluvial plain, flows in a northeast direction, from Atures rapids down to Piacoa atBarrancas
Delta Amacuro – 200 km (120 mi) long that empties into the Gulf of Paría and the Atlantic Ocean, a very largedelta, some 22,500 km2 (8,700 sq mi) and 370 km (230 mi) at its widest.
Orinoco in Mariusa National Park (Delta Amacuro)Orinoco at its confluence with theCaroní River (lower left)[21]Rapids of the Orinoco, near Puerto Ayacucho airport, VenezuelaOrinoco inAmazonas State, VenezuelaOrinoco in Amazonas State, Venezuela
At its mouth, the Orinoco River forms a wide delta that branches off into hundreds of rivers and waterways that flow through 41,000 km2 (16,000 sq mi) of swampy forests. In the rainy season, the Orinoco River can swell to a breadth of 22 km (14 mi) and a depth of 100 m (330 ft). Thestream gradient of the entire river is 0.05% (1,047 m [3,435 ft] over 2,250 km [1,400 mi]). Downstream of Raudales de Guaharibos the gradient is 0.01% (183 m [600 ft][22] over 1,964 km [1,220 mi]), which is also the gradient from Ciudad Bolivar to the ocean (54 m [177 ft] over 435 km [270 mi]).
Encompassing the states ofAnzoategui-Guarico andMonagas states, the Interior Range forms the northern boundary and theGuayana Shield the southern boundary.[23]: 155 Maturin forms the eastern subbasin and Guarico forms the western subbasin.[23]: 156 The El Furrial oil field was discovered in 1978, producing from lateOligocene shallow marinesandstones in anoverthrustedforeland basin.[23]: 155
Most of the important Venezuelan rivers are tributaries of the Orinoco, the largest being theCaroní, which joins it atPuerto Ordaz, close to theLlovizna Falls. A peculiarity of the river system is theCasiquiare canal, which starts as an arm of the Orinoco, and finds its way to the Rio Negro, a tributary of the Amazon River, thus forming adistributary and 'natural canal' between the Orinoco and the Amazon.
Theboto and thegiant otter inhabit the river system.[29] TheOrinoco crocodile is one of the rarest reptiles in the world; its range in the wild is restricted to the middle and lower Orinoco River basin.[30]
More than 1,000 fish species have been recorded in the river basin, and about 15% areendemic.[31] By far the largest orders areCharaciformes andSiluriformes, which together account for more than 80% of the fresh water species.[32] Some of the more famous are theblack spot piranha and thecardinal tetra.[33] Because the Casiquiare canal includes bothblackwater andclear- towhitewater sections, only relatively adaptable species are able to pass through it between the two river systems, such as the cardinal tetra.[34]
The river is navigable for most of its length, anddredging enables ocean ships to go as far as Ciudad Bolívar, at the confluence of the Caroní River, 435 km (270 mi) upstream. River steamers carry cargo as far asPuerto Ayacucho and the Atures Rapids.
In 1926, a Venezuelan mining inspector found one of the richestiron ore deposits near the Orinoco delta, south of the city of San Felix on a mountain namedEl Florero. Full-scale mining of the ore deposits began afterWorld War II, by a conglomerate of Venezuelan firms and US steel companies. In the early 1950s, about 10,000 tons of ore-bearing soil was mined per day.[35]
The river deposits contain extensivetar sands in theOrinoco oil belt, which may be a source of future oil production.[36]
Since 1973, the Civil Association Nuestros Rios son Navegables organize the Internacional RallyNuestros Rios son Navegables, a motonautical round trip of over 1,200 kilometers through the Orinoco, Meta and Apure Rivers. Starting out from Ciudad Bolívar or San Fernando de Apure, is the longest fluvial rally in the world with the participation of worldwide competitors, more than 30 support boats, logistics teams, thousands of tourists and fans travel. The boats had an average speed of 120 miles per hour.
Since 1988, the local government of Ciudad Guayana has conducted a swim race in the Orinoco and Caroní, with up to 1,000 competitors. Since 1991, thePaso a Nado Internacional de los Rios Orinoco–Caroní has been celebrated every year in April. Worldwide, this swim meet has grown in importance, and it has a large number of competitors.[37][38]
^"Orinoquia, Orinoquía".Diccionario panhispánico de dudas. Royal Spanish Academy. 2005. Retrieved2023-01-07.
^"Orinoco River".Encyclopaedia Britannica. Retrieved11 April 2020.
^"Orinoco".Diccionario Etimológico Español en Línea. Retrieved11 April 2020.
^Daum, Andreas W. (2024).Alexander von Humboldt: A Concise Biography. Trans. Robert Savage. Princeton, N.J.: Princeton University Press. pp. 68‒70.ISBN978-0-691-24736-6.
^Helferich, Gerard (2004)Humboldt's Cosmos: Alexander von Humboldt and the Latin American Journey that Changed the Way We See the World, Gotham Books, New York;ISBN1-59240-052-3.
^Alberto Contramaestre Torres. Expedición a las fuentes del Orinoco. Caracas, 1954.
^Pablo J. Anduce.Shailili-Ko. Descubrimiento de las fuentes del Orinoco. Caracas: Talleres Gráficos Ilustraciones S.A., 1960.
^abcPrieto, R., Valdes, G., 1992, El Furrial Oil Field, In Giant Oil and Gas Fields of the Decade, 1978–1988, AAPG Memoir 54, Halbouty, M.T., editor, Tulsa: American Association of Petroleum Geologists,ISBN0891813330
^Thorbjarnarson, John B.; Hernández, Gustavo (1993). "Reproductive ecology of the Orinoco crocodile (Crocodylus intermedius) in Venezuela. I. Nesting ecology and egg and clutch relationships".Journal of Herpetology.27 (4):363–370.doi:10.2307/1564821.JSTOR1564821.
Stark, James H. 1897.Stark's Guide-Book and History of Trinidad including Tobago, Granada, and St. Vincent; also a trip up the Orinoco and a description of the great Venezuelan Pitch Lake. Boston, James H. Stark, publisher; London, Sampson Low, Marston & Company. (This book has an excellent description of a trip up the Orinoco as far asCiudad Bolívar and a detailed description of the VenezuelanPitch Lake situated on the western side of the Gulf of Paria opposite.)
MacKee, E.D., Nordin, C.F. and D. Perez-Hernandez (1998). "The Waters and Sediments of the Rio Orinoco and its major Tributaries, Venezuela and Colombia." United States Geological Survey water-supply paper,ISSN0886-9308 /A-B. Washington: United States Government Printing Office.
Rawlins, C.B. (1999).The Orinoco River. New York: Franklin Watts.
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