Amazônia Basin

The Amazon basin holds as much as 1/5th of the total fresh water in the world (not including the polar caps). Although the majority of the water from rainfall stays in the forest, a huge amount flows out to eventually take the form of the world's greatest river, the Amazon. This mighty giant forms a network of water channels that permeates nearly half the continent of South America.

The Amazon River is fed by more than 1,000 tributaries, including seven that are more than 1,000 miles long, and it drains more than half of Brazil, as well as parts of Bolivia, Peru, Ecuador, Colombia and Venezuela. It discharges more fresh water into the world's oceans than any other river.

On the average, some 28 billion gallons per minute flow into the sea, about 10 times the flow of the Mississippi. The discharge is so great that it noticeably dilutes the salinity of the Atlantic's waters for more than 100 miles offshore.

On its long journey to the sea, the Amazon also varies in color. Some of its tributaries are called "white" rivers, though their color is more often a murky yellow. Others are known as "black" rivers, such as the Negro River.

The white rivers rise in the Andes, and their turbidity results from heavy loads of mud and silt. The black rivers, in contrast, rise in areas of ancient basement rock where little sediment remains to be washed away. It is dissolved organic matter that stains their clarity.

 

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