The River Basins

The Amazon Basin, in northern and western Brazil, takes up more than a third of the whole country. This basin is plain, broadly based on the Andes and funneling narrowly to the sea, most of the drained area has an elevation of less than 250m. The rainfall is heavy, for the winds from the NE and SE lose their moisture as they approach the Andes. Some few places receive from 3,750 to 5,000 mm a year, though over most of the area is more than from 1,500 to 2,500mm. Much of the basin suffers from annual floods. The region was covered by tropical forest, with little undergrowth except along the watercourses, it is now rapidly cut down. The climate is hot and the humidity high throughout the year.
The River Plate Basin, in the southern part of Brazil, has a more varied surface and is less heavily forested than the Amazon Basin. The land is higher and the climate cooler.