Iguazú National Park is Argentina's 677 km² (261 sq mi) protected area in the north of Misiones Province, created in 1934 around Iguazu Falls. It faces Brazil's larger Iguaçu National Park (1939, about 1,853 km²) across the Iguazu River, which forms the border between the two countries. Together the two parks protect the falls and one of the largest forest preservation areas in South America, and both are UNESCO World Heritage Sites, Argentina's since 1984 and Brazil's since 1986. The falls stretch along a 2.7 km (1.7 mile) edge, break into roughly 275 separate drops (anywhere from 150 to 300 depending on the water level) of 60 to 82 m (197 to 269 ft), and send about half the river's flow into the Devil's Throat. The average flow is about 1,746 m³ per second, and the record is 45,700 m³ per second, set on 9 June 2014.
Two Parks, One River: Iguazú (1934) and Iguaçu (1939)
The name of both the park and the river comes from Guaraní: y, "water", and guasu, "big". A Guaraní legend explains the falls themselves: a deity meant to marry a woman named Naipí, who fled in a canoe with her mortal lover Tarobá, and in his rage the god split the river, condemning the pair to fall forever. People lived here long before either park. Hunter-gatherers of the Eldoradense culture occupied the area about 10,000 years ago; the Guaraní, bringing agriculture, displaced them around 1000 CE. The Spanish conquistador Álvar Núñez Cabeza de Vaca was the first European to record the falls, in 1541 or 1542 depending on the account, and Jesuit missions followed from 1609.
The idea of a park came first from Brazil. In 1876, when Yellowstone was only four years old, the Brazilian engineer André Rebouças urged that the "magnificent Iguaçu waterfalls" be preserved for future generations in his book on the railways of Paraná. Argentina acted first, however, creating Iguazú National Park in 1934. Brazil followed with federal decree 1035 of 10 January 1939, which created Iguaçu National Park in the far west of Paraná State, 17 km (11 miles) from the centre of Foz do Iguaçu. The Brazilian park covers 185,262.5 hectares and runs for about 420 km (260 miles) around its edge, 300 km of it along rivers; it was the first park in Brazil to receive a management plan and is run today by the Chico Mendes Institute for Biodiversity Conservation (ICMBio). Combined, the two sides cover about 260,000 hectares.
The Argentine side is split in two. In 1970 law 18.801 turned the western part into the Iguazú National Reserve, where human activity is allowed; that change made room for an international airport and three hotels. To the southeast, Argentina's park adjoins the 84,000-hectare Urugua-í Provincial Park, created in 1990, and both national parks are part of a proposed Trinational Biodiversity Corridor to link forests in Brazil, Paraguay and Argentina.
The two parks offer different views of the same falls. The falls form a reversed "J", and the border runs through the Devil's Throat. Brazil holds more than 95 per cent of the Iguazu basin but just over 20 per cent of the drops, while almost 80 per cent of the falls lie on the Argentine side. Argentina therefore gets the close-up: a Rainforest Ecological Train carries visitors through the forest to the Paseo Garganta del Diablo, a 1 km walkway that ends directly above the Devil's Throat, with other trails along the upper and lower circuits, boats to San Martín Island and inflatable boats that run close to the falls. Brazil gets the panorama: a walkway along the opposite side of the canyon reaches down to the lower base of the Devil's Throat. Panoramic double-deck buses carrying 72 passengers serve the Brazilian park, and only about 0.3 per cent of its area is open to visitors. Brazil has allowed helicopter flights over the falls; Argentina bans them because of their effect on wildlife. The Brazilian park received 1,550,700 visitors in 2014.
Devil's Throat and the Basalt Steps of Iguazu Falls
The Iguazu River rises in the Serra do Mar near Curitiba and flows west for 1,205 km through Paraná State before meeting the San Antonio River, after which it forms the border. Shortly before it ends, it drops off the edge of a plateau. The falls are a two-step staircase cut into three layers of basalt, with steps of 35 and 40 m (115 and 131 ft). These lavas belong to the Serra Geral formation, about 1,000 m (3,300 ft) thick, in the Paraná Basin. Each flow is capped by 8 to 10 m of hard vesicular basalt, and the contact between hard and softer layers sets the shape of the falls, which are eroding headwards at an estimated 1.4 to 2.1 cm a year.
The Devil's Throat (Garganta del Diablo in Spanish, Garganta do Diabo in Portuguese) is a narrow chasm 80 to 90 m wide and 70 to 80 m deep. To its left, the river forms another 160 to 200 individual falls that merge into a single front in flood; the largest are named San Martín, Adam and Eva, Penoni and Bergano. Islands break the 2.7 km edge into separate cataracts, and about 900 m of it has no water flowing over it at all. The whole Iguazu basin covers about 62,000 km², and below the falls the lower Iguazu runs through a canyon to the Paraná River, 23 km downstream according to the Argentine park, after a total course of 1,320 km. Inside the park the river widens to as much as 1,500 m.
Flow at Iguazu: 1,746 m³ a Second, From the 2006 Drought to the 2014 Flood
Iguazu is often compared with Victoria Falls on the Zambezi. Iguazu is wider, but Victoria has the largest single curtain of water in the world, more than 1,600 m wide and over 100 m high, while Niagara is about 50 m (165 ft) high, a third shorter than Iguazu; on seeing Iguazu, Eleanor Roosevelt is reported to have said "Poor Niagara!" On average flow, though, Iguazu is not the leader. Since the Guaíra Falls upstream on the Paraná were flooded by the Itaipu reservoir in 1982, Iguazu has had the sixth-greatest average annual flow of any waterfall, at 1,746 m³ per second, behind Niagara's 2,400. Its extremes are far larger than Niagara's, however.
The maximum recorded flow at Iguazu, 45,700 m³ per second on 9 June 2014, was more than five times Niagara's record of 8,300. At the other extreme, a severe drought in 2006 cut the flow to 300 m³ per second until early December, unusually long when dry spells normally last only a few weeks. The climate is humid subtropical, with rain all year, and the greatest volumes usually come between December and February. The river's water also swings widely in temperature, from about 15.5 to 29 °C, unlike tropical South American rivers. Our ranking of the most powerful waterfalls puts these flows in a world context.
Jaguars, Coatis and Swifts in the Alto Paraná Atlantic Forest
Both parks lie in the Alto Paraná Atlantic forests ecoregion, and the spray from the falls keeps the forest close to the water especially lush. The Argentine park lists rare and threatened species including the jaguar, jaguarundi, South American tapir, ocelot, anteater, harpy eagle, black-fronted piping guan and yacare caiman, as well as toucans, the vinaceous amazon parrot and a great diversity of butterflies. The Brazilian park adds the giant otter. Trees include the ceibo, or cockspur coral tree, whose flower is Argentina's national flower, along with lapacho trees, palmito palms and the palo rosa, which grows to 40 m.
The South American coati, a ring-tailed member of the raccoon family weighing 2 to 7.2 kg, lives in the forests on both sides of the river. The bird most tied to the falls is the great dusky swift, which roosts around waterfalls, nests in colonies on cliffs beside or behind them, and is known for flying through the curtains of water at Iguazu. The river itself has about 100 native fish species, around 70 per cent of them endemic, partly because the falls isolate the fish above them from those below.
Where the Iguazu Meets the Paraná: The Triple Frontier
Downstream of the falls, the Iguazu joins the Paraná at the tripoint of Argentina, Brazil and Paraguay, known as the Triple Frontier. Each country has put up an obelisk in its national colours at the confluence, and all three countries can be seen from each one. Around it sit three cities: Puerto Iguazú in Argentina, the smallest, with about 82,000 people; Foz do Iguaçu in Brazil, with about 258,000 in 2020; and Ciudad del Este in Paraguay, with 299,255 in 2018. With about 950,000 people in all, it is the most populous tripoint in the world. The Tancredo Neves Bridge links Puerto Iguazú with Foz do Iguaçu, and the Friendship Bridge links Foz do Iguaçu with Ciudad del Este.
Just upstream on the Paraná stands the Itaipu Dam, built by Brazil and Paraguay under a 1973 treaty and completed in 1984, with an installed capacity of 14 GW. Its reservoir, which began filling on 13 October 1982, drowned the Guaíra Falls, which is why Iguazu rose in the world flow rankings. Visitors who want to compare Iguazu with its main rival can read our guide to Victoria Falls, or go deeper into the cataracts themselves in our feature on Iguazu Falls.