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 million km2, with 65% of it inVenezuela and 35% inColombia. It is thefourth largest river in the world bydischarge volume of water (39,000 m3/s atdelta) due to the high precipitation throughout its catchment area (ca 2,300 mm/a). The Orinoco River and its tributaries 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", itself derived from the termsgüiri (paddle) andnoko (place) i.e. a navigable place.[10][11]
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 River and back toCoro. In 1595, after capturing de Berrio to obtain information while conducting an expedition to find the fabled city ofEl Dorado, the EnglishmanSir Walter Raleigh sailed down the river, reaching thesavanna 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 the Andes to the Amazon.[12] He reported on thepink river dolphins and later published extensively on the river's flora and fauna.[13]
The sources of the Orinoco River, located at CerroCarlos Delgado Chalbaud (2º19’05” N, 63º21’42” W), were discovered in 1951 by the French-Venezuelan expedition that went back and 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) to Port of Spain (Trinidad). Aboard aSR.N6 hovercraft, the expedition members followed the Negro river 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 thru perilous rapids of the rivers Maipures and Atures. The Orinoco was then traversed down to its mouths in the Gulf 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 powerline crossing of the Orinoco River was completed in 1981 for an 800kVTL single span of 1,200 metres (3,900 ft) using two towers 110 metres (360 ft) tall.[17]
In 1992, an overhead power line crossing for two 400kV-circuits was completed just west of Morocure (between the cities ofCiudad Bolívar andCiudad Guayana), north of the confluence of Routes1 and 19. It had three towers, and the two spans measured 2,161 metres (7,090 ft) and 2,537 metres (8,323 ft), respectively.[17][18][19][20]
The course of the Orinoco 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 kilometres (178 mi) long, from its headwaters to the Raudales de Guaharibos rapids, flows through mountainous landscape in a northwesterly direction
Middle Orinoco – 805 kilometres (500 mi) long, divided into two sectors, the first of which ca. 515 kilometres (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 kilometres (180 mi), along the Venezuelan–Colombian 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 kilometres (596 mi) long with a well-developed alluvial plain, flows in a northeast direction, from Atures rapids down to Piacoa in front ofBarrancas
Delta Amacuro – 200 kilometres (120 mi) long that empties into theGulf of Paría and the Atlantic Ocean, a very largedelta, some 22,500 km2 (8,700 sq mi) and 370 kilometres (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 kilometres (14 mi) and a depth of 100 metres (330 ft).
Most of the important Venezuelan rivers are tributaries of the Orinoco River, the largest being theCaroní, which joins it atPuerto Ordaz, close to theLlovizna Falls. A peculiarity of the Orinoco river system is theCasiquiare canal, which starts as an arm of the Orinoco, and finds its way to theRio Negro, a tributary of theAmazon, thus forming a 'natural canal' between Orinoco and Amazon.
Thestream gradient of the entire river is 0.05% (1,047 m over 2,250 km). Downstream of Raudales de Guaharibos the gradient is 0.01% (183[22]/1,964), which is also the gradient from Ciudad Bolivar to the ocean (54/435).
Theboto and thegiant otter inhabit the Orinoco 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 1000 fish species have been recorded in the river basin and about 15% areendemic.[31] Among the fish in the river are species found inbrackish or salt water in the Orinocoestuary, but also many restricted to fresh water. 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. The latter species, which is important in the aquarium industry, is also found in theRio Negro, revealing the connection between this river and the Orinoco through theCasiquiare canal.[33] Because the Casiquiare includes bothblackwater andclear- towhitewater sections, only relatively adaptable species are able to pass through it between the two river systems.[34]
The river is navigable for most of its length, anddredging enables ocean ships to go as far asCiudad Bolívar, at the confluence of theCaroní River, 435 kilometres (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. At the start in the early 1950s, about 10,000 tons of ore-bearing soil was mined per day.[35]
Encompassing the states ofAnzoategui-Guarico andMonagas states, the Interior Range forms the northern boundary and theGuayana Shield the southern boundary.[37]: 155 Maturin forms the eastern subbasin and Guarico forms the western subbasin.[37]: 156 The El Furrial oil field was discovered in 1978, producing from lateOligocene shallow marinesandstones in anoverthrustedforeland basin.[37]: 155
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 ofCiudad Guayana has conducted a swim race in the rivers Orinoco andCaroní, with up to 1,000 competitors. Since 1991, thePaso a Nado Internacional de los Rios Orinoco–Caroní has been celebrated every year, on a Sunday close to 19 April. Worldwide, this swim-meet has grown in importance, and it has a large number of competitors.[38] The 26th meet was held in 2016.[39]
The Irish singer and songwriter Enya wrote and sang the song "Orinoco Flow", which she released in 1988.[40]Jules Verne's novel Superbe Orénoque has the river as its central theme.
^"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.
^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.
^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
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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