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The Liquid Forest RIVERS, STREAMS, AND CREEKS RIVERS Tropical rainforest rivers are often overwhelming to the first time visitor because of their size and abundance. Even more perplexing is the knack of tropical rivers to fork into large branches, forming giant islands that can be easily confused with the mainland. It is sometimes nearly impossible to distinguish which is the main fork of the river. Overhead pictures of tropical rivers reveal another curious aspect: the meandering course. A river will twist and turn, sometimes turning almost 180¡ back on itself. The lack of slope and the clay-like soils of many tropical regions allow rivers to have virtually free reign over their direction. The volume of water flowing through tropical forests, coupled with the soils and varying water levels, can create great river cliffs over 100 feet high, even at regular water levels. These clay banks in form an important part in the local ecology in parts of the Amazon. Macaws gather by the hundreds on some of these banks to ingest minerals that bind to, and detoxify chemicals in the fruits they consume. The force of water of larger rivers like the Amazon means that bizarre objects are always floating by. It is common to see giants logs and trees passing, though sometimes natural meadow rafts, complete with trees and animals and sometimes a shack, are seen. STREAMS AND CREEKS Tropical streams and creeks are even more variable than tropical rivers, changing from a virtually dry river bed to a raging torrent 30 feet deep in a matter of hours during a heavy rain. Tropical streams, within the rainforest, are interesting because of their surprising depth despite their small width. In the Amazon, because of the clay soils, have a shape that seems to defy the laws of physics. The stream bed of a placid stream may be 15 feet wide,
Creeks are common in the rainforest and provide an important niche for certain fish, amphibian, and insect species in addition to providing an important source of water for other forest floor dwellers. THE GREAT RAINFOREST RIVERS OF THE WORLD THE AMAZON The Amazon River is the most voluminous river on Earth, eleven times the volume of the Mississippi, and drains an area equivalent in size to the United States. During the high water season, the river's mouth may be 300 miles wide and up to 500 billion cubic feet per day (5,787,037 cubic feet/sec) flow into the Atlantic. For reference, the Amazon's daily freshwater discharge into the Atlantic is enough to supply New York City's freshwater needs for nine years. The force of the current, from sheer water volume alone and virtually no gradient, causes the current to continue flowing 125 miles out to sea before mixing with Atlantic salt water. Early sailors could drink freshwater out of the ocean before sighting the South American continent. The river current carries tons of suspended sediment causing the characteristic muddy whitewater appearance. It is calculated that 106 million cubic feet of suspended sediment are swept into the ocean each day. The result from the silt deposited at the mouth of the Amazon, is Majaro island, the world's largest river island about the size of Switzerland. THE ZAIRE The Zaire or Congo River, is Africa's most powerful river and the second most voluminous river (not counting the Madeira and Negro which are considered part of the Amazon) in the world with 1,500,000 cubic feet of water passing out of it mouth every second. It is the fifth longest river in the world, draining a basin of nearly 1.5 million square miles. The river is best known for its role in history. Known as the heart of darkness by Joseph Conrad, the river and surrounding rainforest have long been known as the mysterious land of pygmies, mythical beasts, dreadful plagues, and cannibals. It is a land made famous by the rigorous adventures of Stanley and Livingstone, and known as a place of brutality and violence for its past: the days of the Arab slave and ivory trade, its long history of tribal warfare; and its present: the ethnic violence and massacres of today. The river itself is as turbulent as its history, though it begins peacefully enough in the savannas just south of Lake Tanganyika. Gradually the river widens and picks up speed until it enters the "Gates of Hell," a 75-miles long canyon of impassable rapids. The river emerges again, surrounded by lush tropical rainforest as the Lualaba or Upper Congo. During the course its journey through the foreboding rainforest, the river crosses the equator twice. Because the watershed of the Congo drains from both the Northern and Southern Hemisphere it does not have the great seasonal fluctuations in water level as other great rivers. Its flow is relatively stable because part of its watershed is always in the zone of rain. The Upper Congo abruptly ends with Stanley Falls, a 60 mile stretch of rapids. Stanley Falls gives way to the Middle Congo, a 1000 mile stretch of navigable river, nine miles wide in some parts. Along this quiet stretch of river is the city of Kinsangani, a city known for violence since Belgian colonial days. Near the end of the Middle Congo, the river slows to a virtual stand-still for 20 miles, a section known as Stanley or Malebo Pool. Here the river is 15 miles wide and flanked by the capital cities of Kinshasa and Brazzaville. The peace of the pool is suddenly shattered by Livingstone Falls, a series of rapids and cataracts 220 miles long. There are some 32 cataracts, having as much power as all the river and falls in the United States combined. The final 100 miles to the Atlantic ocean from the end of the falls is fully navigable. THE NIGER RIVER The 2590 mile (4170 km) course of Africa's third largest river was one of the great mysteries of Africa until the mid nineteenth century. From its origins in Guinea less than 150 miles (240 km) from the Atlantic, the river heads north into the Sahara desert. At Timbuktu, the legendary city of gold, the river turns east, then abruptly south back towards the Gulf of Guinea. The river splits into 23 real mouths in the coastal mangrove forests of Nigeria, some of which are only navigable by canoe. The Niger Delta is one of the world's largest wetlands, covering more than 7700 square miles (20,000 square km), and houses Africa's largest mangrove forest. It is the river's great arc and seeming lack of a mouth that made its course so elusive. It was long speculated that the river was a tributary of the Nile or Zaire (Congo) River. The river was first thoroughly explored by the Scotsman Mungo Park, who drowned in a rapid during an expedition. The mouth of the river was discovered in 1830 and by the turn of the century, had become the focus of European attentions for its rich oil deposits. Today, Nigeria depends gravely on these oil reserves to fuel its economy. |
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Rainforest Waters |
Types of Rivers Flooding, Low, and High Water Life by the River Threats to Rivers |
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