The Amazon river has by far the greatest total flow of any river, carrying more than the Mississippi, Nile, and Yangtze rivers combined. Scientists say that is also the longest (4250 miles) after the recent studies. Its drainage area, called the Amazon Basin, is the largest of any river system.
The Amazon River (occasionally River Amazon; Spanish: Río Amazonas, Portuguese: Rio Amazonas) of South America is one of the two longest rivers on Earth, the other being the Nile in Africa. The Amazon has by far the greatest total flow of any river, carrying more than the Mississippi, Nile, and Yangtze rivers combined — so while it may not be the longest river, it is undoubtedly the largest; it is also known as The River Sea. Its drainage area, called the Amazon Basin, is the largest of any river system.
The quantity of fresh water released to the Atlantic Ocean is enormous: up to 300,000 m³ per second in the rainy season. Indeed, the Amazon is responsible for a fifth of the total volume of fresh water entering the oceans worldwide. It is said that 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 a hundred miles out to sea.
The main river (which is usually between one and six miles wide) is navigable for large ocean steamers to Manaus, 1,500 km (more than 900 miles) upriver from the mouth. Smaller ocean vessels of 3,000 tons and 5.5 m (18 ft) draft can reach as far as Iquitos, 3,600 km (2,250 miles) from the sea. Smaller riverboats can reach 780 km (486 mi) higher as far as Achual Point. Beyond that, small boats frequently ascend to the Pongo de Manseriche, just above Achual Point.
The Amazon drains an area of some 6,915,000km² (2,722,000 mile²), or some 40 percent of South America. 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; and, after a course of about 6,400 km (4,000 mi) through the interior of Peru and across Brazil, it enters the Atlantic Ocean at the equator.
The Amazon has changed its drainage several times, from westward in the early Cenozoic to its present eastward locomotion following the uplift of the Andes.