The Amazon River in South America is the second longest river in the world and by far the largest by waterflow with an average discharge greater than the next seven largest rivers combined (not including Madeira and Rio Negro, which are tributaries of the Amazon). The Amazon, which has the largest drainage basin in the world, about 7,050,000 square kilometres, accounts for approximately one-fifth of the world’s total river flow.
The Amazon Basin, the largest in the world, covers about 30% of South America, an area of approximately 7,050,000 square kilometres. It flows from west to east from Iquitos in Peru to all the way across Brazil to the Atlantic. 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 width of the Amazon varies between 1.6 and 10 kilometres at low stage, but expands during the wet season to 48 kilometres or more. The river enters the Atlantic Ocean in a broad estuary about 240 kilometres wide. The mouth of the main stem is 80 kilometres. Because of its vast dimensions, it is sometimes called The River Sea. At no point is the Amazon crossed by a bridge. This is not because of its huge dimensions; in fact, for most of its length (which is 4,080 miles), 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 or cities, limiting the need for crossings.
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 5,400,000 square kilometres. It is the richest tropical forest in the world in terms of biodiversity. There are over 2,100 species of fish currently recognized in the Amazon Basin, with more being discovered every year.
The Amazon is one of the main habitats of the boto, also known as the Amazon River Dolphin. It is the largest species of river dolphin, and it can grow to lengths of up to 2.6 metres. The color of its skin changes with age. It varies from gray when it is young, to pink and white as it matures. The dolphins use sonar to navigate and hunt in the river’s tricky depths. 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 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.
The Amazonian fish fauna is the center of diversity for Neotropical fishes, of which more than 5,600 species are currently known.The bull shark has been reported 4,000 kilometres 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 fresh water fish in the world, reportedly with a maximum length in excess of 4.5 metres and weight up to 200 kilograms.Another Amazonian fresh water fish is the arowana, such as the Silver arowana , which is also a predator and very similar to the arapaima, but only reaches a length of maximum 120 centimetres . Also present in large numbers is the notorious piranha, a carnivorous fish which congregates in large schools, and may attack livestock and even humans. There are approximately from 30 to 60 species of piranha. However, only a few of its species are known to attack humans, most notably Pygocentrus nattereri, the Red-bellied Piranha. The candirú are a number of general parasitic, fresh water catfish in the family Trichomycteridae; all are native to the Amazon River.The strongly electric electric eel and more than 100 species of weakly-electric fishes Gymnotiformes also inhabit the Amazon Basin.