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Amazon River

The Amazon River (; ; (US); (UK)) of South America is the largest river in the world by volumetric discharge, with a total river flow greater than the next ten largest rivers combined. The Amazon, which has the largest drainage basin in the world, accounts for approximately one-fifth of the world's total river flow.Tom Sterling: Der Amazonas. Time-Life Bucher 1979, 8th German Printing, p. 19

In its upper stretches the Amazon river is called Apurimac (in Peru) and Solimoes (in Brazil).

During the wet season, parts of the Amazon exceed in width. Because of its vast dimensions, it is sometimes called The River Sea. At no point is the Amazon crossed by bridges. This is not because of its huge dimensions; in fact, for most of its length, the Amazon's width is well within the capability of modern engineers to bridge. However, the bulk of the river flows through tropical rainforest, where there are few roads and even fewer cities, so there is no need for crossings.

While the Amazon is the largest river in the world by most measures, the current consensus within the geographic community holds that the Amazon is the second longest river, just slightly shorter than the Nile. However, some scientists, particularly from Brazil and Peru, dispute this (see section below).

Drainage area

The Amazon Basin, the largest drainage basin in the world, covers about 40 percent of South America, an area of approximately . It gathers its waters from 5 degrees north latitude to 20 degrees south latitude. Its most remote sources are found on the inter-Andean plateau, just a short distance from the Pacific Ocean.

The Amazon River and its tributaries more than triples over the course of a year. In an average dry season, of land are water-covered, while in the wet season, the flooded area of the Amazon Basin rises to .

The quantity of water released by the Amazon to the Atlantic Ocean is enormous: up to per second in the rainy season. The Amazon is responsible for about 20% of the total volume of freshwater entering the ocean. Potable water can be drawn from the ocean while still out of sight of the coastline, and the salinity of the ocean is notably lower out to sea.

There is a natural water union between the Amazon and the Orinoco basins, the so-called Casiquiare canal. Actually the Casiquiare is a river distributary of the upper Orinoco, which flows southward into the Rio Negro, which in turn flows into the Amazon. The Casiquiare is the largest river on the planet that links two major river systems, a so-called bifurcation..


The Amazon river has a series of major river systems in Peru and Ecuador, some of which flow into the Maranon and Ucayali, others directly into the Amazon proper. Among others, these include the following rivers: Morona, Pastaza, Nucuray, Urituyacu, Chambira, Tigre, Nanay, Napo, and Huallaga.

The most distant source of the Amazon was firmly established in 1996, 2001 and 2007 as a glacial stream on a snowcapped peak called Nevado Mismi in the Peruvian Andes, roughly west of Lake Titicaca and southeast of Lima. The waters from Nevado Mismi flow into the Quebradas Carhuasanta and Apacheta, which flow into the Rio Apurimac which is a tributary of the Ucayali which later joins the Maranon to form the Amazon proper. Soon thereafter the darkly colored waters of the Rio Negro meet the sandy colored Rio Solimoes, and for over these waters run side by side without mixing.

After the confluence of Rio Apurimac and Ucayali, the river leaves Andean terrain and is instead surrounded by floodplain. From this point to the Maranon, some , the forested banks are just out of water, and are inundated long before the river attains its maximum flood-line. The low river banks are interrupted by only a few hills, and the river enters the enormous Amazon Rainforest.

The river systems and flood plains in Brazil, Peru, Ecuador, Colombia and Venezuela whose waters drain into the Solimoes and its tributaries are called the "Upper Amazon".

The Amazon River proper runs mostly through Brazil and Peru, and it has tributaries reaching into Venezuela, Colombia, Ecuador, and Bolivia.


Not all of the Amazon's tributaries flood at the same time of the year. Many branches begin flooding in November, and may continue to rise until June. The rise of the Rio Negro starts in February or March, and it also begins to recede in June. The Madeira rises and falls two months earlier than most of the rest of the Amazon.

The average depth of the river in the height of the rainy season is and the average width can be nearly .

The main river (which is between approximately one and six miles wide) is navigable for large ocean steamers to Manaus, upriver from the mouth. Smaller ocean vessels of 3,000 tons or 9,000 tons and draft can reach as far as Iquitos, Peru, from the sea. Smaller riverboats can reach higher as far as Achual Point. Beyond that, small boats frequently ascend to the Pongo de Manseriche, just above Achual Point.


At some points, for long distances, the river divides into two main streams with inland and lateral channels, all connected by a complicated system of natural canals, cutting the low, flat igapo lands, which are never more than above low river, into many islands.

From the town of Canaria at the great bend of the Amazon to the Negro, only very low land is found, resembling that at the mouth of the river. Vast areas of land in this region are submerged at high water, above which only the upper part of the trees of the sombre forests appear. Near the mouth of the Rio Negro to Serpa, nearly opposite the river Madeira, the banks of the Amazon are low, until approaching Manaus, they rise to become rolling hills. At Obidos, a bluff above the river is backed by low hills. The lower Amazon seems to have once been a gulf of the Atlantic Ocean, the waters of which washed the cliffs near Obidos.

Only about 10% of the water discharged by the Amazon enters the mighty stream downstream of Obidos, very little of which is from the northern slope of the valley. The drainage area of the Amazon Basin above Obidos city is about 5 million square kilometres , and, below, only about 1 million square kilometres , exclusive of the 1.4 million square kilometres of the Tocantins basin.

In the lower reaches of the river, the north bank consists of a series of steep, table-topped hills extending for about from opposite the mouth of the Xingu as far as . These hills are cut down to a kind of terrace which lies between them and the river.

On the south bank, above the Xingu, an almost-unbroken line of low bluffs bordering the flood-plain extends nearly to Santarem, in a series of gentle curves before they bend to the south-west, and, abutting upon the lower Tapajos, merge into the bluffs which form the terrace margin of the Tapajos river valley.


The definition of what exactly and how wide is the mouth of the Amazon is a matter of dispute, because of the area's peculiar geography. Most particularly, sometimes the Para River is included, whereas sometimes it is just considered the independent lower reach of the Tocantins River. The Para river estuary alone is wide. The Para and the Amazon are connected by a series of river channels called furos near the town of Breves; between them lies Marajo, an island almost the size of Switzerland that is the world's largest combined river/sea island.

If the Para river and the Marajo island ocean frontage are included, the Amazon estuary is some wide. In this case, the width of the mouth of the river is usually measured from Cabo Norte, in the Brazilian state of Amapa, to Ponta da Tijoca near the town of Curuca, in the state of Para. By this criterion, the Amazon is wider at its mouth than the entire length of the River Thames in England.

A more conservative measurement excluding the Para river estuary, from the mouth of the Araguari River to Ponta do Navio on the northern coast of Marajo, would still give the mouth of the Amazon a width of over . If only the river's main channel is considered, between the islands of Curua (state of Amapa) and Jurupari (state of Para), the width falls to just about - but that is still impressive for any river.

Tidal bore (pororoca)

The tension between the river's strong push and the Atlantic tides causes a phenomenon called a tidal bore, a powerful tidal wave that flows rapidly inland from the sea up the Amazon mouth and nearby coastal rivers several times a year at high tide. Tidal bores also occur in other river mouths around the world, but the Amazon's are among the world's highest and fastest, probably second only to those of Qiantang River in China. In the Amazon, the phenomenon is locally known as the pororoca.

The pororoca occurs especially where depths do not exceed . It starts with a very loud roar, constantly increasing, and advances at the rate of with a breaking wall of water high that may travel violently several kilometres up the Amazon and other rivers close to its mouth. It is particularly intense in the rivers of the coast of the state of Amapa north of the mouth of the Amazon, such as the Araguari River, but can be observed in Para rivers as well.

The bore is the reason the Amazon does not have a protruding delta; the ocean rapidly carries away the vast volume of silt carried by the Amazon, making it impossible for a delta to grow past the shoreline. The region also has very high tides, sometimes reaching and has become a popular spot for river surfing.


More than one-third of all species in the world live in the Amazon Rainforest, a giant tropical forest and river basin with an area that stretches more than 5.4 million square kilometres (2.1 million sq mi), and is the richest tropical forest in the world. The Amazon River has over 3,000 recognized species of fish and that number is still growing.

Along with the Orinoco, the river is one of the main habitats of the boto, also known as the Amazon River Dolphin (Inia geoffrensis). It is the largest species of river dolphin, and it can grow to lengths of up to . The boto is the subject of a very famous legend in Brazil about a dolphin that turns into a man and seduces maidens by the riverside. The tucuxi (Sotalia fluviatilis), also a dolphin species, is found both in the rivers of the Amazon Basin and in the coastal waters of South America.

The Amazonian Manatee is another conspicuous mammal living in the waters of the Amazonian basin.

Also present in large numbers is the notorious piranha, a carnivorous fish which congregates in large schools, and may attack livestock and even humans. However, only a few of its species are known to attack humans, most notably Pygocentrus nattereri, the Red-bellied Piranha.

The bull shark (Carcharhinus leucas) has been reported up the Amazon River at Iquitos in Peru. The arapaima, known in Brazil as the pirarucu (Arapaima gigas), is a South American tropical freshwater fish. It is one of the largest freshwater fish in the world, reportedly with a maximum length in excess of and weight up to . Megafishes Project to Size Up Real "Loch Ness Monsters". National Geographic. Another Amazonian freshwater fish is the arowana (or aruana in Portuguese), such as the Silver arowana (Osteoglossum bicirrhosum), which is also a predator and very similar to the arapaima, but only reaches a length of maximum . The candiru are a number of genera of parasitic, freshwater catfish in the family Trichomycteridae; all are native to the Amazon River. They sometimes attack humans and have been known to enter the urethras of bathers. The electric eel (Electrophorus electricus) is also found in the river.

The anaconda snake is found in shallow waters in the Amazon Basin. One of the world's largest species of snake, the anaconda spends most of its time in the water, with just its nostrils above the surface. In addition to the thousands of species of fish, the river supports crabs, algae, and turtles.

Colonial encounters with the Amazon

During what many archaeologists call the formative period, Amazonian societies were deeply involved in the emergence of South America's highland agrarian systems, and possibly contributed directly to the social and religious fabric constitutive of the Andean civilizational orders.

In 1515, Vicente Yanez Pinzon was the first European to sail into the river. Pinzon called the river flow Rio Santa Maria del Mar Dulce, later shortened to Mar Dulce . For 350 years after the first European encounter of the Amazon by Pinzon, the Portuguese portion of the basin remained an untended former food gathering and planned agricultural landscape occupied by the indigenous peoples who survived the arrival of European diseases. There is ample evidence for complex large-scale, pre-Columbian social formations, including chiefdoms, in many areas of Amazonia (particularly the inter-fluvial regions) and even large towns and cities. For instance the pre-Columbian culture on the island of Marajo may have developed social stratification and supported a population of 100,000 people. The Native Americans of the Amazon rain forest may have used Terra preta to make the land suitable for the large scale agriculture needed to support large populations and complex social formations such as chiefdoms.

One of Gonzalo Pizarro's lieutenants, Francisco de Orellana, set off in 1541 to explore east of Quito into the South American interior in search of El Dorado and the "Country of Cinnamon". He was ordered to follow the Coca River and return when the river reached its confluence. After 170 km, the Coca River joined the Napo River (at a point now known as Puerto Francisco de Orellana), and his men threatened to mutiny if he followed his orders and the expedition turned back. On 26 December 1541, he accepted to change the purpose of the expedition to the conquest of new lands in the name of the King of Spain, and the 49 men built a larger boat in which to navigate downstream. After a journey of 600 km down the Napo River, constantly threatened by the Omaguas, they reached a further major confluence, at a point near modern Iquitos, and then followed what is now known as the Amazon River for a further 1200 km to its confluence with the Negro River (near modern Manaus), which they reached on 3 June 1542. This area around the Amazon was dominated by the Icamiaba natives, who were mistaken for fierce female warriors by the members of the expedition. Orellana later narrated the belligerent victory of the Icamiaba women over the Spanish invaders to Charles V, Holy Roman Emperor, who, recalling the Amazons of Greek mythology, baptized the river Amazonas, the name by which it is still known in both Spanish and Portuguese. At the time, however, the river was referred to by the expedition as Grande Rio ("Great River"), Mar Dulce ("Freshwater Sea") or Rio de la Canela ("Cinnamon River"). Orellana claimed that he had found great cinnamon trees there, in other words a source of one of the most important spices reaching Europe from the East. In fact, true cinnamon (Cinnamomum verum) is not native to South America. Other related cinnamon-containing plants (of the family Lauraceae) do occur and Orellana must have observed some of these. The expedition continued a further 1200 km to the mouth of the Amazon, which it reached on 24 August 1542, demonstrating the practical navigability of the Great River. This was surely one of the most improbably successful voyages in known history.

In 1560 another Spanish conquistador, Lope de Aguirre, made the second descent of the Amazon.

In 163747 the Portuguese explorer Pedro Teixeira was the first European to ascend the river from Belem (near the mouth of the Amazon) to Quito, part of the Spanish Viceroyalty of Peru, and then to return the same way. Teixeira's expedition was massive - some 2000 people in 37 large canoes. From 1648 to 1652, Antonio Raposo Tavares lead one of the longest known expeditions from Sao Paulo to the mouth of the Amazon, investigating many of its tributaries, including the Rio Negro, and covering a distance of more than .

In what is currently Brazil, Ecuador, Bolivia, Colombia, Peru, and Venezuela, a number of colonial and religious settlements were established along the banks of primary rivers and tributaries for the purpose of trade, slaving and evangelization among the indigenous peoples of the vast rain forest. Father Fritz, apostle of the Omaguas, established some forty mission villages. Charles Marie de La Condamine accomplished the first scientific exploration of the Amazon River.

The Cabanagem, one of the bloodiest regional wars ever in Brazil, which was chiefly directed against the white ruling class, reduced the population of Para from about 100,000 to 60,000.

The total population of the Brazilian portion of the Amazon Basin in 1850 was perhaps 300,000, of whom about two-thirds comprised by Europeans and slaves, the slaves amounting to about 25,000. The Brazilian Amazon's principal commercial city, Para (now Belem), had from 10,000 to 12,000 inhabitants, including slaves. The town of Manaos, now Manaus, at the mouth of the Rio Negro, had a population between 1,000 to 1,500. All the remaining villages, as far up as Tabatinga, on the Brazilian frontier of Peru, were relatively small.

Post-colonial history

On 6 September 1850, the emperor, Pedro II, sanctioned a law authorizing steam navigation on the Amazon, and gave the Viscount of Maua (Irineu Evangelista de Sousa) the task of putting it into effect. He organized the "Companhia de Navegacao e Comercio do Amazonas" in Rio de Janeiro in 1852; and in the following year it commenced operations with three small steamers, the Monarch, the Marajo and Rio Negro.

At first, navigation was principally confined to the main river; and even in 1857 a modification of the government contract only obliged the company to a monthly service between Para and Manaus, with steamers of 200 tons cargo capacity, a second line to make six round voyages a year between Manaus and Tabatinga, and a third, two trips a month between Para and Cameta. This was the first step in opening up the vast interior.

The success of the venture called attention to the opportunities for economic exploitation of the Amazon, and a second company soon opened commerce on the Madeira, Purus and Negro; a third established a line between Para and Manaus; and a fourth found it profitable to navigate some of the smaller streams. In that same period, the Amazonas Company was increasing its fleet. Meanwhile, private individuals were building and running small steam craft of their own on the main river as well as on many of its tributaries.

On 31 July 1867 the government of Brazil, constantly pressed by the maritime powers and by the countries encircling the upper Amazon basin, especially Peru, decreed the opening of the Amazon to all flags; but limited this to certain defined points: Tabatinga — on the Amazon; Cameta — on the Tocantins; Santarem — on the Tapajos; Borba — on the Madeira, and Manaus — on the Rio Negro. The Brazilian decree took effect on 7 September 1867.

Thanks in part to the mercantile development associated with steamboat navigation, coupled with the internationally driven demand for natural rubber (18801920), Manaos (now Manaus) and Para (now Belem) in (Brazil), and Iquitos, Peru became thriving, cosmopolitan centers of commerce and spectacular — albeit illusory — "modern" "urban growth". This was particularly the case for Iquitos during its late 19th and early 20th century Rubber Bonanza zenith when this dynamic boomtown was known abroad as the St. Louis of the Amazon.

The first direct foreign trade with Manaus was commenced around 1874. Local trade along the river was carried on by the English successors to the Amazonas Company — the Amazon Steam Navigation Company — as well as numerous small steamboats, belonging to companies and firms engaged in the rubber trade, navigating the Negro, Madeira, Purus and many other tributaries, such as the Maranon to ports as distant as Nauta, Peru. The Amazon Steam Navigation Company had 38 vessels.

By the turn of the 20th century, the principal exports of the Amazon Basin were India-rubber, cacao beans, Brazil nuts and a few other products of minor importance, such as pelts and exotic forest produce and extracted goods .

20th century concerns

Four centuries after the European discovery of the Amazon river, the total cultivated area in its basin was probably less than , excluding the limited and crudely cultivated areas among the mountains at its extreme headwaters. This situation changed dramatically during the 20th century.

Wary of foreign exploitation of the nation's resources, Brazilian governments in the 1940s set out to develop the interior, away from the seaboard, where foreigners owned large tracts of land. The original architect of this expansion was President Getulio Vargas, with the demand for rubber from the Allied forces in World War II providing funding for the drive.

In 1960, the construction of the new capital city of Brasilia in the interior also contributed to the opening up of the Amazon Basin. A large-scale colonization program saw families from Northeastern Brazil relocated to the forests, encouraged by promises of cheap land. Many settlements grew along the road from Brasilia to Belem, but rainforest soil proved difficult to cultivate.

Still, long-term development plans continued. Roads were cut through the forests, and in 1970, the work on the Trans-Amazonian highway (Transamazonica) network began. The network's three pioneering highways were completed within ten years, but never fulfilled their promise. Large portions of the Trans-Amazonian and its accessory roads, such as BR-319 (Manaus-Porto Velho), are derelict and impassable in the rainy season.

With a current population of 1.8 million people, Manaus is the Amazons largest city. Manaus alone represents approximately 50% of the population of the Brazilian state of Amazonas, which is the largest state. The racial makeup of the city is 64% Pardo (Mulatto and mestizo) and 32% White.

Dispute regarding length

While debate as to whether the Amazon or the Nile is the world's longest river has gone on for many years, the historic consensus of geographic authorities has been to regard the Amazon as the second longest river in the world, with the Nile being the longest. However, the Amazon has been measured by different geographers as being anywhere between 6,259 and 6,800 kilometres long. The Nile is reported to be anywhere from 5,499 to 6,690 kilometres The differences in these measurements often result from the use of different definitions.

A study by Brazilian scientists claimed that the Amazon is actually longer than the Nile. Using Nevado Mismi, which in 2001 was labeled by the National Geographic Society as the Amazon's source, these scientists have made new calculations of the Amazon's length. They now estimate that the Amazon is longer than the Nile, and Guido Gelli, director of science at the Brazilian Institute of Geography and Statistics (IBGE), told the Brazilian TV network Globo in June 2007 that it could be considered as a fact that the Amazon was the longest river in the world. However, other geographers have had access to the same data since 2001, and a consensus has yet to emerge to support the claims of these Brazilian scientists.

Major tributaries

The Amazon has over 1,100 tributaries in total, 17 of which are over .Tom Sterling: Der Amazonas. Time-Life Bucher 1979, 8th German Printing, p. 20 Some of the more notable ones are:


Casiquiare canal

Caqueta River


Putumayo (or Ica River)



















Longest rivers in the Amazon system

- Amazon, South America

- Purus, Peru / Brazil,

- Madeira, Bolivia / Brazil

- Yapura, Colombia / Brazil

- Tocantins, Brazil,

- Araguaia, Brazil (tributary of Tocantins)

- Jurua, Peru / Brazil

- Rio Negro, Brazil / Venezuela / Colombia

- Xingu, Brazil

- Tapajos, Brazil

- Guapore, Brazil / Bolivia (tributary of Madeira)

- Ucayali River, Peru

- Ica (Putumayo), South America

- Maranon, Peru

- Teles Pires, Brazil (tributary of Tapajos)

- Iriri, Brazil (tributary of Xingu)

- Juruena, Brazil (tributary of Tapajos)

- Madre de Dios, Peru / Bolivia (tributary of Madeira)

- Huallaga, Peru (tributary of Maranon)

External links

Amazon dries up Youtube (31 July 2006)

Amazon Rainforest Fund

Bibliography on Water Resources and International Law Peace Palace Library

Information on the Amazon from Extreme Science

Pictures of the Amazon River

Information and a map of the Amazon's watershed

Amazon Alive: Light & Shadow documentary film about the Amazon river

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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article Amazon River

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