The Iguazu River ( , ), also called Rio Iguassu, (from the Guaraní ''í Guazú'', literally "Big Water") is a river in

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

and

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

. It is an important tributary of the

Paraná River The Paraná River ( ; ; ) is a river in south-central South America, running through Brazil, Paraguay, and Argentina for some ."Parana River". Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica Inc., 2012. Web. ...

. The Iguazu River is long, with a

drainage basin A drainage basin is an area of land in which all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, ...

of .

Course

The Iguazu originates in the

Serra do Mar The Serra do Mar (; ) is a system of mountain ranges and escarpments in Southeast Region, Brazil, Southeastern Brazil. Geography The Serra do Mar runs parallel to the Atlantic Ocean coast from the state of Espírito Santo to southern Santa Ca ...

coastal mountains of the Brazilian state of Paraná and close to

Curitiba Curitiba () is the capital and largest city in the state of Paraná (state), Paraná in Southern Brazil. The city's population was 1,773,718 , making it the List of cities in Brazil by population, eighth most populous city in Brazil and the larg ...

. For , to its confluence with the

San Antonio River The San Antonio River is a major waterway that originates in central Texas in a cluster of springs in midtown San Antonio, about 4 miles north of downtown, and follows a roughly southeastern path through the state. It eventually feeds into the ...

, the Iguazu flows west through Paraná State, Brazil. Downriver from the confluence, the Iguazu River forms the boundary between Brazil and Argentina's

Misiones Province Misiones (, ''Missions'') is one of the Provinces of Argentina, 23 provinces of Argentina, located in the northeastern corner of the country in the Mesopotamia, Argentina, Mesopotamia region. It is surrounded by Paraguay to the northwest, Brazil ...

. Continuing west, the river drops off a plateau, forming

Iguazu Falls Iguazú Falls or Iguaçu Falls ( , ; ; Tupi: Y Ûasu "big water") are waterfalls of the Iguazu River on the border of the Argentine province of Misiones and the Brazilian state of Paraná. Together, they make up the largest waterfall sys ...

, which are accessible via the Rainforest Ecological Train. The falls are within national parks in both Brazil,

Iguaçu National Park Iguaçu National Park () is a National park (Brazil), national park in Paraná State, Brazil. It comprises a total area of and a length of about , of which are natural borders by bodies of water and the Argentine and Brazilian sides together c ...

, and Argentina, Iguazú National Park. It empties into the Paraná River at the point where the borders of Argentina, Brazil, and

Paraguay Paraguay, officially the Republic of Paraguay, is a landlocked country in South America. It is bordered by Argentina to the Argentina–Paraguay border, south and southwest, Brazil to the Brazil–Paraguay border, east and northeast, and Boli ...

join, an area known as the

Triple Frontier The Triple Frontier (, ) is a tri-border area along the junction of Argentina, Brazil and Paraguay, where the Iguazu River, Iguazú and Paraná River, Paraná rivers converge. Near the confluence are the cities of Puerto Iguazú (Argentina), ...

Ecology

Unlike tropical South American rivers, where the annual variations in temperature are relatively limited, the water in the

subtropical The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones immediately to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Ge ...

Iguazu River varies significantly depending on season. At two sites, one located just above and another just below the falls, the water at both varied from about , and average was just below .Nardelli, Bueno, Ludwig, and Guimarães (2016).
Structure and dynamics of the planktonic diatom community in the Iguassu River, Paraná State, Brazil.
' Braz. J. Biol. 76(2). The pH is typically near-neutral, ranging from 5.9 to 8.7. About 100 fish species are native to the Iguazu River, and several

undescribed species In taxonomy, an undescribed taxon is a taxon (for example, a species) that has been discovered, but not yet formally described and named. The various Nomenclature Codes specify the requirements for a new taxon to be validly described and named. U ...

are known.Daga, Debona, Abilhoa, Gubiani & Vitule (2016). ''Non-native fish invasion of Neotropical ecoregion with high endemism: a review of the Iguaçu River.'' Aquatic Invasions 11(2): 209-223.Baumgartner, Pavanelli, Baumgartner, Bifi, Debona & Frana (2012).
Peixes do baixo rio Iguaçu.
' EDUEM. DOI:10.7476/9788576285861 Most fish species in the river are

catfish Catfish (or catfishes; order (biology), order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Catfish are common name, named for their prominent barbel (anatomy), barbels, which resemble a cat's whiskers, though not ...

characiform Characiformes is an order of Actinopterygii, ray-finned fish, comprising the characins and their allies. Grouped in 18 recognized families, more than 2000 different species are described, including the well-known piranha and tetras.; Buckup P.A ...

s and

cichlid Cichlids () are a large, diverse, and widespread family of percomorph fish in the family Cichlidae, order Cichliformes. At least 1,760 species have been scientifically described, making it one of the largest vertebrate families, with on ...

s.Piálek, Dragová, Casciotta, Almirón & Řičan (2015). ''Description of two new species of Crenicichla (Teleostei: Cichlidae) from the lower Iguazú River with a taxonomic reappraisal of C. iguassuensis, C. tesay and C. yaha.'' Historia Natural 5(2): 5-27. About 70% are

endemic Endemism is the state of a species being found only 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 foun ...

, which to a large extent is linked to the falls, serving both as a home for

rheophilic A rheophile is an animal that prefers to live in fast-moving water. Examples of rheophilic animals Insects *Many aquatic insects living in riffles require current to survive. *'' Epeorus sylvicola'', a rheophilic mayfly species ( Ephemeroptera ...

species and isolating species above and below. This also means that, except for the threatened '' Steindachneridion melanodermatum'' in the lower part, large migratory fish known from much of the Paraná River Basin are naturally absent from Iguazu. Almost 30

introduced species An introduced species, alien species, exotic species, adventive species, immigrant species, foreign species, non-indigenous species, or non-native species is a species living outside its native distributional range, but which has arrived ther ...

are found in the river where about one-third originate from other continents (such as

carp The term carp (: carp) is a generic common name for numerous species of freshwater fish from the family (biology), family Cyprinidae, a very large clade of ray-finned fish mostly native to Eurasia. While carp are prized game fish, quarries and a ...

largemouth bass The largemouth bass (''Micropterus nigricans'') is a carnivorous, freshwater fish, freshwater, ray-finned fish in the Centrarchidae (sunfish) family, native to the eastern United States, eastern and central United States, southeastern Canada an ...

tilapia Tilapia ( ) is the common name for nearly a hundred species of cichlid fish from the coelotilapine, coptodonine, heterotilapine, oreochromine, pelmatolapiine, and tilapiine tribes (formerly all were "Tilapiini"), with the economically mos ...

and African sharptooth catfish) and the remaining from elsewhere in South America (such as

dorado Dorado (, ) is a constellation in the Southern Sky. It was named in the late 16th century and is now one of the 88 modern constellations. Its name refers to the mahi-mahi (''Coryphaena hippurus''), which is known as ''dorado'' ("golden") in Sp ...

, '' Cichla kelberi'',

pacu Pacu () is a common name used to refer to several species of omnivorous South American freshwater Serrasalmidae, serrasalmid fish related to piranhas. Pacu and piranha do not have similar teeth, the main difference being jaw alignment; piranha ...

, '' Brycon hilarii'', ''

Prochilodus lineatus ''Prochilodus lineatus'', the streaked prochilod, is a species of ray-finned fish in the family Prochilodontidae. It is native to the Paraná River, Paraná—Paraguay River, Paraguay and Paraíba do Sul River, Paraíba do Sul river basins in So ...

'' and ''

Odontesthes bonariensis ''Odontesthes bonariensis'' is a species of Neotropical silverside, an euryhaline fish native to fresh, brackish and salt water in south-central and southeastern South America, but also Introduced species, introduced elsewhere. It is often known ...

''). The unusual '' Aegla'' crustacean are locally common in the Iguazu River Basin.

Environmental issues

In July 2000 more than of

crude oil Petroleum, also known as crude oil or simply oil, is a naturally occurring, yellowish-black liquid chemical mixture found in geological formations, consisting mainly of hydrocarbons. The term ''petroleum'' refers both to naturally occurring u ...

spilled into the river from a state-run oil refinery in the municipality of

Araucária Araucária is a municipality in the Brazilian state of Paraná. The population in 2020 was 146,214 inhabitants. History The first movement of the white man in today Araucaria Brazil, dating back to the year 1668,period in which Domingos Rodr ...

near

References

{{Authority control Rivers of Argentina Rivers of Brazil Tributaries of the Paraná River International rivers of South America Rivers of Paraná (state) Rivers of Misiones Province Foz do Iguaçu Border rivers Argentina–Brazil border

Course

Ecology

Environmental issues

See also

References