The Rio Negro ( pt, Rio Negro, br ; es, Río Negro} "''Black River''"), or Guainía as it is known in its upper part, is the largest left
tributary
A tributary, or affluent, is a stream or river that flows into a larger stream or main stem (or parent) river or a lake. A tributary does not flow directly into a sea or ocean. Tributaries and the main stem river drain the surrounding drai ...
of the
Amazon River (accounting for about 14% of the water in the
Amazon basin
The Amazon basin is the part of South America drained by the Amazon River and its tributaries. The Amazon drainage basin covers an area of about , or about 35.5 percent of the South American continent. It is located in the countries of Boli ...
), the largest
blackwater river in the world, and one of the world's ten
largest rivers by average discharge.
Geography
Upper course
The source of the Rio Negro lies in Colombia, in the
Department of Guainía where the river is known as the ''Guainía River''.
The young river generally flows in an east-northeasterly direction through the
Puinawai National Reserve, passing several small indigenous settlements on its way, such as Cuarinuma, Brujas, Santa Rosa and Tabaquén. After roughly 400 km the river starts forming the border between Colombia's
Department of Guainía and Venezuela's
Amazonas State. After passing the Colombian community of Tonina and Macanal the river turns Southwest.
Maroa is the first Venezuelan town the river passes.
120 km further downstream the river receives the
Casiquiare canal
The Casiquiare river () is a distributary of the upper Orinoco flowing southward into the Rio Negro, in Venezuela, South America. As such, it forms a unique natural canal between the Orinoco and Amazon river systems. It is the world's largest ...
from the left (north), forming a unique link between the
Orinoco
The Orinoco () is one of the longest rivers in South America at . Its drainage basin, sometimes known as the Orinoquia, covers , with 76.3 percent of it in Venezuela and the remainder in Colombia. It is the fourth largest river in the wor ...
and the Amazon river basin. Henceforth the river is called ''Rio Negro''.
Middle course
The river now continues in a southeastern direction passing the Venezuelan town of
San Carlos de Río Negro, its largest settlement on the river, and Colombia's
San Felipe.
In this stretch the river is constantly fed with tributaries from both sides, and it quickly grows in size creating large river islands, a common feature for all rivers in the Amazon basin. After forming the border between Colombia and Venezuela for 260 km the Rio Negro reaches the
Piedra del Cocuy, an igneous rock formation from the Precambrian era, belonging to the
Guyana Shield
The Guiana Shield (french: Plateau des Guyanes, Bouclier guyanais; nl, Hoogland van Guyana, Guianaschild; pt, Planalto das Guianas, Escudo das Guianas; es, Escudo guayanés) is one of the three cratons of the South American Plate. It is a 1 ...
. Here the
Tripoint of Colombia, Venezuela and Brazil is found in the middle of the river and it now completely enters
Amazonas State, Brazil
Amazonas () is a state of Brazil, located in the North Region in the northwestern corner of the country. It is the largest Brazilian state by area and the 9th largest country subdivision in the world, and the largest in South America, bein ...
. After passing
Cucuí, the river continues south, only temporarily turning west for several kilometers. In
Missão Boa Vista the
Içana River
Içana River (río Isana/río Içana in Spanish and Portuguese) is a tributary of the Rio Negro in South America. Its source is in the Guainía Department of Colombia, where it is known as the Isana River. From its source, it flows mostly east u ...
joins the Rio Negro and in São Joaquim the
Uaupes River, the largest tributary of the Rio Negro, also enters from the right hand side. The Rio Negro now turns markedly towards the east, forming several rapids and small islets on its way. It then passes
Sao Gabriel da Cachoeira an important commercial city. After several more rapids and imposing views of the Adormecida mountain chain the river leaves the Guyana shield it traversed in its upper and middle course.
Lower course
After the
Marié River enters the Rio Negro the river continues its eastward course forming many large islands and becoming very wide at several locations. It passes local communities such as
Santa Isabel do Rio Negro. During the
wet season, the river floods the country far and wide here, sometimes to a width of , for long distances. During this season, from April until October, it is a succession of lagoons, full of long islands and intricate channels with a lot of water wildlife. Near Carvoeiro the last major tributary of the Rio Negro, the
Branco River joins the Rio Negro and the river temporarily forms the border between the state of
Roraima and
Amazonas State, Brazil
Amazonas () is a state of Brazil, located in the North Region in the northwestern corner of the country. It is the largest Brazilian state by area and the 9th largest country subdivision in the world, and the largest in South America, bein ...
. The river now takes a more southeastern course, becoming again very wide in many stretches before reaching the biggest city on its course
Manaus.
The
Anavilhanas National Park
Anavilhanas National Park ( pt, Parque Nacional de Anavilhanas) is a national park that encompasses a huge river archipelago in the Rio Negro in the state of Amazonas, Brazil. It is part of a World Heritage Site.
Location
The park is in the mu ...
, a conservation unit that was originally an ecological station created in 1981, protects part of the Anavilhanas river archipelago in this part of the river.
Below the archipelago, it meets the
Solimões River to form the
Amazon River, creating a phenomenon known as the
Meeting of Waters
The Meeting of Waters ( pt, Encontro das Águas) is the confluence between the dark ( blackwater) Rio Negro and the pale sandy-colored ( whitewater) Amazon River, referred to as the Solimões River in Brazil upriver of this confluence. For th ...
.
History
The river was named by the Spanish explorer
Francisco de Orellana, who first came upon it in 1541. By the middle of the 17th century, Jesuits had settled along its banks in the midst of numerous tribes: Manau, Aruák, and Trumá Indians. After 1700 slaving along the river was common, and
Native American populations were greatly diminished after contact with Eurasian diseases.
This area was the filming location for Survivor:The Amazon in 2003.
Fauna and Flora
While the name ''Rio Negro'' means ''Black River'', its waters are similar in color to strong
tea, which is typical of
blackwater rivers. The dark color comes from
humic acid due to an incomplete breakdown of phenol-containing vegetation from sandy clearings. The river was named because it looks black from a distance.
Much has been written on the productivity of the Rio Negro and other blackwater rivers. The older idea that these are "hunger rivers" is giving way, with new research, to the recognition that the Rio Negro, for example, supports a large fishing industry and has numerous turtle beaches. If explorers did not find many
Indigenous peoples
Indigenous peoples are culturally distinct ethnic groups whose members are directly descended from the earliest known inhabitants of a particular geographic region and, to some extent, maintain the language and culture of those original people ...
along the Rio Negro during the 17th century, it is likely that their populations were reduced because of new infectious diseases and warfare rather than low river productivity.
Rio Negro has a very high
species richness. About 700 fish species have been documented in the river basin, and it is estimated that the total is 800–900 fish species, including almost 100
endemics
Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...
and several
undescribed species.
[Hales, J., and P. Petry (2013). ]
Rio Negro
'. Freshwater Ecoregions of the World. Retrieved 12 February 2013 Among these are many that are important in the
aquarium
An aquarium (plural: ''aquariums'' or ''aquaria'') is a vivarium of any size having at least one transparent side in which aquatic plants or animals are kept and displayed. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, aq ...
trade, including the
cardinal tetra.
[ As a result of the ]Casiquiare canal
The Casiquiare river () is a distributary of the upper Orinoco flowing southward into the Rio Negro, in Venezuela, South America. As such, it forms a unique natural canal between the Orinoco and Amazon river systems. It is the world's largest ...
, many aquatic species are found both in the Rio Negro and Orinoco. Because the Casiquiare includes both blackwater and clear- to whitewater sections, only relatively adaptable species are able to pass through it between the two river systems.
Notes
References
* Goulding, M., Carvalho, M. L., & Ferreira, E. J. G. (1988). ''Rio Negro, Rich Life in Poor Water : Amazonian Diversity and Foodchain Ecology as seen through Fish Communities''. The Hague: SPB Academic Publishing.
* Saint-Paul, U., Berger, U., Zuanon, J., Villacorta Correa, M. A., García, M., Fabré, N. N., et al. (2000). "Fish communities in central Amazonian white- and blackwater floodplains," ''Environmental Biology of Fishes, 57''(3), 235–250.
* Sioli, H. (1955). "Beiträge zur regionalen Limnologie des Amazonasgebietes. III. Über einige Gewässer des oberen Rio Negro-Gebietes." ''Arch. Hydrobiol., 50''(1), 1-32.
* Wallace, A. R. (1853). ''A narrative of travels on the Amazon and Rio Negro, with an account of the native tribes, and observations on the climate, geology, and natural history of the Amazon Valley''. London: Reeve.
* Wright, R. (2005). ''História indígena e do indigenismo no Alto Rio Negro''. São Paulo, Brazil: UNICAMP & Instituto Socioambiental. .
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Negro, Rio
Negro, Rio
Negro, Rio
Negro, Rio
Colombia–Venezuela border
International rivers of South America
Amazon basin
Ramsar sites in Brazil
Border rivers