The Amazon 

The Amazon River

The Amazon basin (or catchment) occupies approximately 7 million square kilometers in the North Central part of South America. Most of it is in Brazil, but it also includes parts of Bolivia, Colombia, Ecuador, Guyana, and small parts of French Guiana, Surinam and Venezuela. The amazon basin covers 58.5% of the area of Brazil. It is estimated that the Amazon discharges between 34 and 121 million liters of water per second and deposits a daily average of 3 million tons of sediment near its mouth. The annual outflow from the river accounts for one-fifth of all the fresh water that drains into the oceans of the world. The outpouring of water and sediment is so vast that the salinity and color of the Atlantic Ocean are altered for a distance of about 320 km from the mouth of the river.

The major headstreams of the Amazon are the Ucayali and Maranón rivers, both of which rise in the permanent snows and glaciers of the high Andes Mountains and follow parallel courses north before joining near Nauta, Peru. From this confluence the main trunk of the Amazon flows in a generally eastern direction to the Atlantic Ocean. The Amazon enters the Atlantic through a broad estuary, roughly estimated at 240 km (about 150 mi) in width. Here delta deposits have formed a maze of islands that separate the river into branches. The mouth of the main stream is 80 km (50 mi) wide. This branch, known as the Pará, is separated from a smaller branch by Marajó Island, which has an area of more than 36,000 sq km (14,000 sq mi). During new and full moon a tidal bore, or wave front from the ocean, sweeps some 650 km (more than 400 mi) upstream at speeds in excess of 65 km/hr (40 mph). This phenomenon often causes waves up to 5 m (16 ft) in height.
 

The Amazon and its changeable Seasons 

The Amazon catchment includes the largest and wettest tropical plain in the world. Heavy rains drench much of the densely forested lowland region throughout the year but especially between January and June. The width, rate of flow, and discharge volume of the river reflect seasonal variation. During the months of maximum precipitation, broad areas crossed by the Amazon are subject to severe floods. In Brazil the width of the river ranges between 1.6 and 10 km (1 and 6 miles) at low water but expands to 48 km (30 miles) or more during the annual floods. The rate of flow ranges between 2.4 and 8 km/hr (1.5 and 5 mph); and the crest of the water at flood time often rises 15 m (50 ft) above normal. To drain the vast mass of water, the Amazon has carved a deep bed in the plain through which it flows. In one section near Óbidos, the bed is more than 91 metres (300 ft) below the average surface level of its water. 

Because of its size, annual floods, and navigability, the Amazon is often called the Ocean River. The total number of its tributaries is not yet known, but more than 200 are in Brazil alone. Seventeen of the largest tributaries are more than 1,600 km in length. The Amazon proper is navigable to ocean liners of virtually any tonnage for two-thirds of its course. Transatlantic ships call regularly at Manaus, nearly 1,600 km upstream, and ships of 3,000 tons can reach Iquitos, Peru, 3,700 km from the river's mouth, the farthest point from sea of any port serving ocean traffic. River steamers of more modest tonnage can navigate on more than 100 of the larger tributaries. 

Amazonian Fauna
 

The Amazon forest contains the largest single reserve of biological organisms in the world. No one really knows how many species there are in the Amazon forest, but scientists estimate that there are between 800,000 and 5 million species living there, amounting to 15 to 30 percent of all the species in the entire world. As naturalists catalogue new species of freshwater fish, their findings suggest that there may be as many as 3,000 kinds of fish in the Amazon's rivers and lakes. 

Piranha 

Among the specialized fish found in the area are: the pirarucu, said to be the largest freshwater fish in the world with specimens measuring over 2 meters in length and weighing 125 kilograms; the tambaqui, which have teeth that can crack seeds as hard as those of the rubber tree and the jauari palm; and the piranha. The ferocity of the meat-eating piranha has been exaggerated. Although it is true that some species in rare circumstances have killed large animals and even people, their behavior depends on the state of their habitat. In main river channels and in larger lakes with plenty of food they generally leave swimmers unmolested. They appear to become aggressive only when they do not have enough nourishment. 

Exploration and Development

Vicente Yáñez Pinzón may have discovered the delta region of the Amazon in 1500, but exploration did not begin until 1540-41, when an expedition led by Francisco de Orellana started down the Napo River, in what is now Ecuador, and reached the Atlantic Ocean. Pedro Teixeira undertook the first upstream voyage. Between October 1637 and August 1638 he ascended the Amazon to the source of the Napo River and crossed the Andes to Quito, Ecuador. Later, he returned by the same route. In modern times the river has been explored by many scientific expeditions, including that led by Theodore Roosevelt and others sponsored by the National Geographic Society and the
government of Brazil in 1914.

Native American 

Some authorities believe that the river was named after the Amazons, women warriors of Greek mythology who were thought to reside in the region; other scholars insist that the name is derived from the Native American word amassona ("boat destroyer"). Despite centuries of effort to overcome the dominance of nature, people have made little impact on the Amazon and most of its vast drainage basin. No bridge spans the river. Except near its mouth, the Amazon watershed constitutes one of the most thinly populated regions in the world. Much of the territory drained by the river system has never been thoroughly explored. One may fly for hours over the tropical forests that cover much of the river's floodplain and see no sign of human settlement. In many valleys, Native American tribes hostile to strangers continue to live much as they did before the arrival of the Europeans. Most commerce is narrowly confined to the navigable sections of the river system. The economy continues to be dominated by primitive agriculture, hunting and fishing, and the gathering of various forest products. 

Commercial farming, tourism, and industry play only a minor role in the region, but manufacturing, mining and lumbering, the principal economic activities, are increasingly important. Manaus, the largest settlement, is once again one of Brazil's major cities. In the 1980's Brazil, under pressure from international conservation groups, started to ensure that efforts to develop the Amazon did not irrevocably compromise the nation's forest resources. Recent discoveries of oil and gas place further pressures. However, the Brazilian government is active in promoting sustainable exploitation of the huge resources in the Amazon. Environmental monitoring and licensing systems have been set up. National Parks conserve the flora and fauna. The rights of Indians are now recognized and their ways of life are protected in reserves.