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| The Liquid Forest |
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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 ability 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 degrees back on itself. The lack of slope and the clay-like soils of many tropical regions allow rivers to have virtually free rein over their direction.
With their huge volume, large rivers like the Amazon transport tremendous quantities of wood and debris. It is common to see giant logs and trees passing, though sometimes natural meadow rafts, complete with trees and animals and sometimes a shack, are seen floating downstream. Often river navigation is complicated by massive logjams that form in river channels. The Rio Madeira, a sizeable tributary of the Amazon, gets its name from the large amounts of wood that pass down the river. These logjams, along with sunken wood, provide a critical habitat for fish and other aquatic animals. STREAMS AND CREEKS
Some of these creeks, especially in lowland Amazonia, can be surprisingly deep with a U-shaped riverbed. The clay substrate helps these creeks keep their form and seemingly defy the laws of physics. 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) may 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 fresh water 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 its 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 is known as a place of brutality and violence in the days of the Arab slave and ivory trade, its long history of tribal warfare, and the ethnic violence and massacres of today.
Stanley Falls gives way to the Middle Congo, a 1,000-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 standstill 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
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 attention for its rich oil deposits. Today, Nigeria depends on these oil reserves to fuel its economy. The forests of the Niger River delta and Nigeria overall are fast declining. According to the Food and Agriculture Organization of the United Nations (FAO), Nigeria has the world's highest deforestation rate of primary forests. Between 2000 and 2005 the country lost 55.7 percent of its primary forests—defined as forests with no visible signs of past or present human activities. Review questions:
[full photo version] Continued: Flooding, Low Water, High Water Bibliographic citation for this page Other pages in this section: |
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