The Amazon River of South America is the largest river in the world by volume, with a total river flow greater than the next eight 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. During the wet season parts of the Amazon exceed 190 kilometres (120 mi) 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.

The Amazon basin, the largest drainage basin in the world, covers about 40 percent of South America, an area of approximately 6,915,000 square kilometres (2,670,000 sq mi) . 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 area covered by the water of the Amazon River and its tributaries more than triples over the course of a year. In an average dry season 110,000 square kilometres (42,000 sq mi)of land are water-covered, while in the wet season the flooded area of the Amazon Basin rises to 350,000 square kilometres (135,000 sq mi) .

 

The quantity of water released by the Amazon to the Atlantic Ocean is enormous: up to 300,000 m³ per second in the rainy season. The Amazon is responsible for about 20% of the total volume of freshwater entering the oceans worldwide. Offshore of the mouth of the Amazon, 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 five hundred kilometres out to sea.

 

Origins
 
The Upper Amazon has a series of major river systems in Peru and Ecuador, some of which flow into the Marañón and others directly into the Amazon proper. Among others, these include the following rivers: Morona, Pastaza, Nucuray, Urituyacu, Chambira, Tigre, Nanay, Napo, Huallaga, and Ucayali. The headstreams of the Marañón—which for many years had been seen as the origin of the Amazon—flow from high above central Peru's Lake Lauricocha, from the glaciers in what is known as the Nevado de Yarupa. Rushing through waterfalls and gorges in an area of the high jungle called the pongos, the Marañón River flows about 1,600 kilometres (990 mi) from west-central to northeast Peru before it combines with the Ucayali River, just below the provincial town of Nauta, to form the Amazon River.

 

The most distant source of the Amazon was firmly established in 1996, 2001 and 2007 as a glacial stream on a snowcapped 5,597 m (18,360 ft) peak called Nevado Mismi in the Peruvian Andes, roughly 160 km (99 mi) west of Lake Titicaca and 700 km (430 mi) southeast of Lima. The waters from Nevado Mismi flow into the Quebradas Carhuasanta and Apacheta, which flow into the Río Apurímac which is a tributary of the Ucayali which later joins the Marañón to form the Amazon proper. (While this is the point at which most geographers place the beginning of the Amazon proper, in Brazil the river is known at this point as the Solimões das Águas). Soon thereafter the darkly colored waters of the Rio Negro meet the sandy colored Rio Solimões, and for over 6 km (4 mi) these waters run side by side without mixing.

 

After the confluence of Río Apurímac and Ucayali, the river leaves Andean terrain and is instead surrounded by floodplain. From this point to the Marañón, some 1,600 km (990 mi) , 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 Solimões 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.

 

 

Geography
 
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 5 metres (16 ft) 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 Óbidos, a bluff 17 m (56 ft) 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 Óbidos.

 

Only about 10% of the water discharged by the Amazon enters the mighty stream downstream of Óbidos, very little of which is from the northern slope of the valley. The drainage area of the Amazon basin above Óbidos city is about 5 million square kilometres (2,000,000 sq mi), and, below, only about 1 million square kilometres (400,000 sq mi or around 20%), exclusive of the 1.4 million square kilometres (540,000 sq mi) 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 240 kilometres (150 mi) from opposite the mouth of the Xingu as far as Monte Alegre [disambiguation needed]. 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 Santarém, in a series of gentle curves before they bend to the south-west, and, abutting upon the lower Tapajós, merge into the bluffs which form the terrace margin of the Tapajós river valley.

 

 

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 (2,100,000 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. Some estimates go as high as 5,000.

 
Along with the Orinoco, the river is one of the main habitats of the boto, also known as the Amazon river dolphin (Inia geoffrensis). The largest species of river dolphin, it can grow to lengths of up to 2.6 metres (8.5 ft). 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) is a dolphin found both in the rivers of the Amazon Basin and in the coastal waters of South America.

 

Also present in large numbers are the notorious piranha, carnivorous fish which congregate in large schools, and may attack livestock and even humans. However, only a few species attack humans, and many are solely fish-eaters, and do not school.

 

The bull shark (Carcharhinus leucas) has been reported 4,000 km (2,500 mi) up the Amazon River at Iquitos in Peru. The arapaima, known in Brazil as 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 3 m (9.8 ft) and weight up to 200 kg (440 lb). Another Amazonian freshwater fish is the arowana (or aruanã in Brazil) (Osteoglossum bicirrhosum) which is also a predator and very similar to the arapaima, but reaches a length of maximum 120 centimetres. The candirú are a number of genera of parasitic freshwater catfish in the family Trichomycteridae; all are native to the Amazon River. It sometimes attacks humans and has been known to enter the urethras of bathers. The electric eel (Electrophorus electricus) is found in the Amazon River basin.

 

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.

The river supports thousands of species of fish, as well as crabs, algae, and turtles.

 

Sources:

 

^ a b Tom Sterling: Der Amazonas. Time-Life Bücher 1979, 8th German Printing, p. 19
^ "Amazon (river)". Microsoft Encarta Online Encyclopedia. Archived from the original on 2009-10-31. http://www.webcitation.org/5kwDrOAQJ. Retrieved 2007-08-12. 
^ Source of the Amazon River Identificated (Jacek Palkiewicz)
^ Explorers Pinpoint Source of the Amazon (National Geographic News)
^ Amazon river 'longer than Nile' (BBC news) (2007-06-16)
^ Amazon uk.encarta.msn.com. Retrieved 1 October 2006. Archived 2009-10-31.
^ "Pororoca: surfing the Amazon". http://fogonazos.blogspot.com/2007/03/pororoca-surfing-amazon.html. Retrieved 2008-08-01. 
^ Amazon rainforest fact sheet
^ Megafishes Project to Size Up Real "Loch Ness Monsters". National Geographic.