River

A river is a big, natural waterway. Passage via a river is the usual way rainfall finds its way to an ocean or other large body of water such as a lake.

Table of contents 1 Topography 2 Biology 3 Pollution 4 Dams 5 Flooding 6 Transport 7 River list 8 Fiction

Topography

A river conducts water by constantly flowing perpendicular to the elevation curve of its bed, thereby converting the positional energy of the water into kinetic energy. As a river flows over relatively flat areas, the river will often meander: start to form loops and snake through the plain through erosion of the river banks. Loops of the river occasionally are cut off, forming a shorter riverbed and leaving an oxbow lake[?]. Erosion caused by rivers often cause them to develop deltas at their mouths, consisting of mazes of river arms and islands made up of the silt deposited as the river loses speed, eventually fading into the ocean or lake.

Where a river descends quickly, rapids with whitewater or even waterfalls may occur. Rapids are often used for recreational purposes, see Whitewater canoeing[?] and kayaking. Waterfalls are commonly used as sources of energy, via watermills and hydroelectric plants.

Biology

The flora and fauna of rivers are much different from those of the oceans because the water is sweet (non-salty). All living things in a river must be adapted to the current of the moving water.

Pollution

Human pollution of rivers is very common, and very few rivers in the world today are clean of artificial substances. Most common is unfiltered sewage being piped into rivers, but chemical pollution is also common, and industrial accidents (and/or negligence) account for much of the destructon of riparian biomes. Heat dumped into rivers by power plants[?] and factories also affects river life.

Dams

In places where the elevation changes of a river are great, dams for hydroelectric plants and other purposes are often built. This disrupts the natural flow of the river, and creates a lake behind the dam. Often the building of dams affects the whole of the river, even the part above the dam, as migrating fish are hindered and waterflow is no longer bounded by seasonal changes. One very famous, and problematic, dam is the Aswan High Dam in the Nile.

Flooding

Flooding is a natural part of a river's cycles. Human activity, however, has upset the natural way flooding occurs by walling off rivers and straightening their courses. Removal of bogs, swamps and other wetlands in order to produce farmland has reduced the absorption zones for excess water and made floods into sudden disasters rather than gradual increases in water flow. In ancient Egypt, life was made possible through the floods of the Nile and the accompanying silt and sediment which enriched the fields with fresh nutrients. Nowadays, floods are disasters, causing untold property loss each year.

Transport

• Sailing
• barge
• riverboat[?] (with swallow hull and paddle wheel)
• river ferry[?]
• towpath

River list

See: List of waterways

The world´s ten longest rivers:

• Nile (6,690 Km).
• Amazon (6,280 Km).
• Mississipi-Missouri (6,270 Km).
• Ob-Irtysh (5,570 Km).
• Zaire (4,670 Km).
• Amur (4,410 Km).
• Huang Ho (Yellow) (4,350 Km).
• Lena (4,260 Km).
• Yangtze (4,090 Km).
• Mackenzie (4,040 Km).

Well-known rivers (in alphabetic order) include:

• Aa - multiple rivers in Europe
• Amazon - largest river in South America
• American
• Amu Darya
• Amur - principal river of eastern Siberia
• Arno - river through Florence
• Chang Jiang (Yangtse)
• Chao Phraya - principal river of Thailand
• Colorado (Argentina)
• Colorado (U.S.) - principal river of American Southwest[?]
• Columbia - principal river of Pacific Northwest
• Congo - principal river of central Africa
• Danube - principal river of southeastern Europe
• Euphrates - twin principal river of Mesopotamia
• Ganges - principal river of India
• Hari Rud
• Huang He (Yellow) - principal river of China
• Hudson - principal river of New York
• Indus - principal river of Pakistan
• Lena - principal river of northeastern Siberia
• Magdalena[?] - principal river of Colombia
• Mekong - principal river of Southeast Asia
• Main
• Mississippi - principal river of central United States
• Missouri - principal river of the Great Plains
• Murray - principal river of southeastern Australia
• Niger - principal river of west Africa
• Nile - longest river in the world
• Ob - large river of Siberia
• Odra
• Ohio - largest river between Mississippi and Appalachians
• Orinoco - principal river of Venezuela
• Rhine - principal river of northwestern Europe
• Rhône - principal river of southern France
• Rio Grande - border between United States and Mexico
• Seine - river of Paris
• Saint Lawrence - drains Great Lakes
• Tay - largest river in Scotland
• Thames - river of London
• Tigris - twin principal river of Mesopotamia
• Vistula - principal river of Poland
• Volga - principal river of Russia
• Yenisei - large river of Siberia
• Zambezi - principal river of southeastern Africa

See also:

• Physical geography
• Rivers of Europe
• Rivers of Asia
• Rivers of Africa
• Rivers of the Americas
• Basin[?]

Fiction

Chocolate river in Willy Wonka and the Chocolate Factory.