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Melting Toe of Athabasca Glacier, Jasper National Park, Alberta, Canada.
The beginning of a mountain river in the Swiss Alps, Switzerland. (Reichenbach in Grosse Scheidegg)
This bridge across the Danube River links Hungary with Slovakia.
A view across the Brahmaputra from near Sukleswar ghat in Guwahati, India.
A river is a natural watercourse,[1] usually freshwater, flowing toward an ocean, a lake, a sea or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including stream, creek, brook, rivulet, and rill; there is no general rule that defines what can be called a river. An exception to this is the stream. In some countries or communities a stream may be defined by its size. Many names for small rivers are specific to geographic location; one example is Burn in Scotland and North-east England. .Sometimes a river is said to be larger than a creek,[2] but this is not always the case, because of vagueness in the language.^ Because of the difficulty of crossing rivers, they have sometimes become territorial boundaries.
  • River Systems of the World 12 January 2010 5:52 UTC www.rev.net [Source type: FILTERED WITH BAYES]

[3]
A river is part of the hydrological cycle. Water within a river is generally collected from precipitation through surface runoff, groundwater recharge, springs, and the release of stored water in natural ice and snowpacks (e.g., from glaciers).

Contents

Topography

The water in a river is usually confined to a channel, made up of a stream bed between banks. In larger rivers there is also a wider floodplain shaped by flood-waters over-topping the channel. Flood plains may be very wide in relation to the size of the river channel. This distinction between river channel and floodplain can be blurred especially in urban areas where the floodplain of a river channel can become greatly developed by housing and industry.
The term upriver refers to the direction leading to the source of the river, which is against the direction of flow. Likewise, the term downriver describes the direction towards the mouth of the river, in which the current flows.
.The river channel typically contains a single stream of water, but some rivers flow as several interconnecting streams of water, producing a braided river.^ Where possible, diverted water may be returned to the river clean and near the point of diversion; specifically, some municipal water supplies treat their sewage and return fairly clean water to the river.
  • River Systems of the World 12 January 2010 5:52 UTC www.rev.net [Source type: FILTERED WITH BAYES]

^ Because flow is not constant, many rivers produce floods and droughts.
  • River Systems of the World 12 January 2010 5:52 UTC www.rev.net [Source type: FILTERED WITH BAYES]

Extensive braided rivers are now found in only a few regions worldwide, such as the South Island of New Zealand. They also occur on peneplains and some of the larger river deltas. Anastamosing rivers are similar to braided rivers and are also quite rare. They have multiple sinuous channels carrying large volumes of sediment.
.A river flowing in its channel is a source of energy which acts on the river channel to change its shape and form.^ New Orleans sits on the delta formed where the Mississippi River flows into the Gulf of Mexico.
  • River Systems of the World 12 January 2010 5:52 UTC www.rev.net [Source type: FILTERED WITH BAYES]

^ Alluvial deposits can form deltas where the river flows into a lake or ocean.
  • River Systems of the World 12 January 2010 5:52 UTC www.rev.net [Source type: FILTERED WITH BAYES]

According to Brahm's law (sometimes called Airy's law), the mass of objects that may be flown away by a river is proportional to the sixth power of the river flow speed. Thus, when the speed of flow increases two times, it can transport 64 times larger (i.e., more massive) objects.[4] In mountainous torrential zones this can be seen as erosion channels through hard rocks and the creation of sands and gravels from the destruction of larger rocks. In U-shaped glaciated valleys, the subsequent river valley can often easily be identified by the V-shaped channel that it has carved. .In the middle reaches where the river may flow over flatter land, meanders may form through erosion of the river banks and deposition on the inside of bends.^ New Orleans sits on the delta formed where the Mississippi River flows into the Gulf of Mexico.
  • River Systems of the World 12 January 2010 5:52 UTC www.rev.net [Source type: FILTERED WITH BAYES]

^ Alluvial deposits can form deltas where the river flows into a lake or ocean.
  • River Systems of the World 12 January 2010 5:52 UTC www.rev.net [Source type: FILTERED WITH BAYES]

.Sometimes the river will cut off a loop, shortening the channel and forming an oxbow lake or billabong.^ Alluvial deposits can form deltas where the river flows into a lake or ocean.
  • River Systems of the World 12 January 2010 5:52 UTC www.rev.net [Source type: FILTERED WITH BAYES]

.Rivers that carry large amounts of sediment may develop conspicuous deltas at their mouths, if conditions permit.^ Farms and cities have been developed on large deltas.
  • River Systems of the World 12 January 2010 5:52 UTC www.rev.net [Source type: FILTERED WITH BAYES]

.Rivers whose mouths are in saline tidal waters may form estuaries.^ Where possible, diverted water may be returned to the river clean and near the point of diversion; specifically, some municipal water supplies treat their sewage and return fairly clean water to the river.
  • River Systems of the World 12 January 2010 5:52 UTC www.rev.net [Source type: FILTERED WITH BAYES]

Throughout the course of the river, the total volume of water transported downstream will often be a combination of the free water flow together with a substantial contribution flowing through sub-surface rocks and gravels that underlie the river and its floodplain (called the hyporheic zone). .For many rivers in large valleys, this unseen component of flow may greatly exceed the visible flow.^ Because flow is not constant, many rivers produce floods and droughts.
  • River Systems of the World 12 January 2010 5:52 UTC www.rev.net [Source type: FILTERED WITH BAYES]

Classification

Although the following classes are a useful way to visualize rivers, there are many other factors at work. Gradient is controlled largely by tectonics, but discharge is controlled largely by climate, and sediment load is controlled by various factors including climate, geology in the headwaters, and the stream gradient.
Youthful river
a river with a steep gradient that has very few tributaries and flows quickly. Its channels erode deeper rather than wider. (Examples: Brazos River, Trinity River, Ebro River)
Mature river
a river with a gradient that is less steep than those of youthful rivers and flows more slowly. A mature river is fed by many tributaries and has more discharge than a youthful river. Its channels erode wider rather than deeper. (Examples: Mississippi River, St. Lawrence River, Danube River, Ohio River, River Thames)
Old river
a river with a low gradient and low erosive energy. Old rivers are characterized by flood plains. (Examples: Huang He River, Ganges River, Tigris, Euphrates River, Indus River, Nile River)
Rejuvenated river
a river with a gradient that is raised by tectonic uplift.
The straight-line distance from the beginning to the end of most rivers is about one third their actual length.[5][6]
The way in which a river's characteristics vary between the upper course and lower course of a river is summarized by the Bradshaw model.
Most rivers flow on the surface; however subterranean rivers flow underground in caves or caverns. Such rivers are frequently found in regions with limestone geologic formations.
An intermittent river (or ephemeral river) only flows occasionally and can be dry for several years at a time. These rivers are found in regions with limited or highly variable rainfall, or can occur because of geologic conditions such as having a highly permeable river bed. Some ephemeral rivers flow during the summer months but not in the winter. Such rivers are typically fed from chalk aquifers which recharge from winter rainfall. In the UK these rivers are called Bournes and give their name to place such as Bournemouth and Eastbourne

Uses

Leisure activities on the River Avon at Avon Valley Country Park, Keynsham, United Kingdom. A boat giving trips to the public passes a moored private boat.
Many riverbanks in Japan are used as places for playing, recreation and parties
Rivers have been used as a source of water, for obtaining food, for transport, as a defensive measure, as a source of hydropower to drive machinery, for bathing, and as a means of disposing of waste.
Rivers have been used for navigation for thousands of years. The earliest evidence of navigation is found in the Indus Valley Civilization, which existed in northwestern Pakistan around 3300 BC.[7] Riverine navigation provides a cheap means of transport, and is still used extensively on most major rivers of the world like the Amazon, the Ganges, the Nile, the Mississippi, and the Indus. Since river boats are often not regulated, they contribute a large amount to global greenhouse gas emissions, and to local cancer due to inhaling of particulates emitted by the transports.[8][9]
In some heavily-forested regions such as Scandinavia and Canada, lumberjacks use the river to float felled trees downstream to lumber camps for further processing, saving much effort and cost by transporting the huge heavy logs by natural means.
Rivers have been a source of food since pre-history.[10] They can provide a rich source of fish and other edible aquatic life, and are a major source of fresh water, which can be used for drinking and irrigation. It is therefore no surprise to find most of the major cities of the world situated on the banks of rivers. Rivers help to determine the urban form of cities and neighbourhoods and their corridors often present opportunities for urban renewal through the development of foreshoreways such as Riverwalks. Rivers also provide an easy means of disposing of waste-water and, in much of the less developed world, other wastes.
Fast flowing rivers and waterfalls are widely used as sources of energy, via watermills and hydroelectric plants. Evidence of watermills shows them in use for many hundreds of years such as in the Orkneys at Dounby click mill. Prior to the invention of steam power, water-mills for grinding cereals and for processing wool and other textiles were common across Europe. In the 1890s the first machines to generate power from river water were established at places such as Cragside in Northumberland and in recent decades there has been a significant increase in the development of large scale power generation from water, especially in wet mountainous regions such as Norway
The coarse sediments, gravel and sand, generated and moved by rivers are extensively used in construction. In parts of the world this can generate extensive new lake habitats as gravel pits re-fill with water. In other circumstances it can destabilise the river bed and the course of the river and cause severe damage to spawning fish populations which rely on stable gravel formations for egg laying.
In upland rivers, rapids with whitewater or even waterfalls occur. Rapids are often used for recreation, such as whitewater kayaking.
Rivers have been important in determining political boundaries and defending countries. For example, the Danube was a long-standing border of the Roman Empire, and today it forms most of the border between Bulgaria and Romania. The Mississippi in North America and the Rhine in Europe are major east-west boundaries in those continents. The Orange and Limpopo Rivers in southern Africa form the boundaries between provinces and countries along their routes.

Ecosystem

The flora and fauna of rivers use the aquatic habitats available, from torrential waterfalls through to lowland mires. Although many organisms are restricted to the fresh water in rivers, some, such as salmon and hilsa, have adapted to be able to survive both in rivers and in the sea. The organisms in the riparian zone respond to changes in river channel location and patterns of flow. For example, in rapidly migrating streams, ecological successions develop in accordance with the prevailing patterns of erosion and deposition.

Chemistry

The chemistry of rivers is complex and depends on inputs from the atmosphere, the geology through which it travels and the inputs from man's activities. The chemistry of the water has a large impact on the ecology of that water for both plants and animals and it also affects the uses that may be made of the river water. Understanding and characterising river water chemistry requires a well designed and managed programme of sampling and analysis
Like many other aquatic ecosystems, rivers too are under increasing threat of pollution. According to a study of the WWF's Global Freshwater Programme, the 10 most polluted rivers are: Ganges, Indus, Yangtze, Salween-Nu, Mekong-Lancang, Rio Grande/Rio Bravo, La Plata, Danube, Nile-Lake Victoria, and the Murray-Darling.[11]

Brackish water

Nile River delta, as seen from Earth orbit. The Nile is an example of a wave-dominated delta that has the classic Greek delta (Δ) shape after which River deltas were named. Photo courtesy of NASA.
Some rivers generate brackish water by having their river mouth in the ocean. This, in effect creates a unique environment in which certain species are found.

Flooding

Flooding is a natural part of a river's cycle. The majority of the erosion of river channels and the erosion and deposition on the associated floodplains occur during flood stage. In many developed areas, human activity has changed river channel form, altering different magnitudes and frequencies of flooding. Some examples of this are the building of levees, the straightening channels, and the draining of natural wetlands. In many cases human activities in rivers and floodplains have dramatically increased the risk of flooding. Straightening rivers allows water to flow more rapidly downstream increasing the risk of flooding places further downstream. Building on flood plains removes flood storage which again exacerbates downstream flooding. The building levees may only protect the area behind the levees and not those further downstream. Levees and flood-banks can also increase flooding upstream because of back-water pressure as the upstream water has to squeeze between the levees.

Flow

Direction

River meandering course
Rivers flow downhill from river source to river mouth, but they do not necessarily take the shortest path. For alluvial streams, straight and braided rivers have very low sinuosity and flow directly down hill, while meandering rivers flow from side to side across a valley. Bedrock rivers typically flow in either a fractal pattern, or a pattern that is determined by weaknesses in the bedrock, such as faults, fractures, or more erodible layers.

Rate

Volumetric flow rate, also called discharge, volume flow rate, and rate of water flow, is the volume of water which passes through a given cross-section of the river channel per unit time. It is typically measured in cubic meters per second (cumec) or cubic feet per second (cfs), where 1 m³/s = 35.51 ft³/s; it is sometimes also measured in litres or gallons per second.
Volumetric flow rate can be thought of as the mean velocity of the flow through a given cross-section, times that cross-sectional area. Mean velocity can be approximated through the use of the Law of the Wall. In general, velocity increases with the depth (or hydraulic radius) and slope of the river channel, while the cross-sectional area scales with the depth and the width: the double-counting of depth shows the importance of this variable in determining the discharge through the channel.

Management

Rivers are often managed or controlled to make them more useful, or less disruptive, to human activity.
  • Dams or weirs may be built to control the flow, store water, or extract energy.
  • Levees, known as dikes in Europe, may be built to prevent river water from flowing on floodplains or floodways.
  • Canals connect rivers to one another for water transfer or navigation.
  • River courses may be modified to improve navigation, or straightened to increase the flow rate.
River management is a continuous activity as rivers tend to 'undo' the modifications made by people. Dredged channels silt up, sluice mechanisms deteriorate with age, levees and dams may suffer seepage or catastrophic failure. The benefits sought through managing rivers may often be offset by the social and economic costs of mitigating the bad effects of such management. As an example, in parts of the developed world, rivers have been confined within channels to free up flat flood-plain land for development. Floods can inundate such development at high financial cost and often with loss of life.
Rivers are increasingly managed for habitat conservation, as they are critical for many aquatic and riparian plants, resident and migratory fishes, waterfowl, birds of prey, migrating birds, and many mammals.

Rating systems

  • International Scale of River Difficulty – The scale is used to rate the challenges of navigation—particularly those with rapids. Class I is the easiest and Class VI is the hardest.
  • Strahler Stream Order – The Strahler Stream Order ranks rivers based on the connectivity and hierarchy of contributing tributaries. Headwaters are first order while the Amazon River is twelfth order. Approximately 80% of the rivers and streams in the world are of the first and second order.

Gallery

See also

Crossings

Transport

References

  1. ^ River {definition} from Merriam-Webster. Accessed February 2010.
  2. ^ "WordNet Search: River". The Trustees of Princeton University. http://wordnetweb.princeton.edu/perl/webwn?s=river&sub=Search+WordNet&o2=&o0=1&o7=&o5=&o1=1&o6=&o4=&o3=&h=. Retrieved 2009-10-02. 
  3. ^ "Domestic Names: Frequently Asked Question (FAQs), #17". United States Geological Survey. http://geonames.usgs.gov/domestic/faqs.htm. Retrieved 2009-10-02. 
  4. ^ Garde, R. J. (1995). History of fluvial hydraulics. New Age Publishers. pp. 19. ISBN 812240815X. OCLC 34628134. http://books.google.com/books?lr=&hl=en&q=%22It+may+also+be+mentioned+that+criterion+for+the+beginning%22. 
  5. ^ Hans-Henrik Stølum: "River Meandering as a Self-Organization Process", Science 271 (5256), 1710
  6. ^ Fermat's last theorem, Simon Singh, 1997
  7. ^ Panda.org
  8. ^ DOI.org
  9. ^ DOI.org
  10. ^ NMP.org
  11. ^ Top 10 most polluted rivers

Further reading


Source material

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From BibleWiki

  1. Heb. 'aphik, properly the channel or ravine that holds water (2 Sam 22:16), translated "brook," "river," "stream," but not necessarily a perennial stream (Ezek 6:3; 31:12; 32:6; 34:13).
  2. Heb. nahal, in winter a "torrent," in summer a "wady" or valley (Gen 32:23; Deut 2:24; 3:16; Isa 30:28; Lam 2:18; Ezek 47:9). These winter torrents sometimes come down with great suddenness and with desolating force. A distinguished traveller thus describes his experience in this matter:, "I was encamped in Wady Feiran, near the base of Jebel Serbal, when a tremendous thunderstorm burst upon us. .After little more than an hour's rain, the water rose so rapidly in the previously dry wady that I had to run for my life, and with great difficulty succeeded in saving my tent and goods; my boots, which I had not time to pick up, were washed away.^ I couldn't see the bottom near the launch, so I wasn't certain if I could have gotten in dry (I wouldn't have wanted that water on/in my booties).
    • Chicago River Paddling/Fishing 12 January 2010 5:52 UTC pages.ripco.net [Source type: FILTERED WITH BAYES]

    .In less than two hours a dry desert wady upwards of 300 yards broad was turned into a foaming torrent from 8 to 10 feet deep, roaring and tearing down and bearing everything upon it, tangled masses of tamarisks, hundreds of beautiful palmtrees, scores of sheep and goats, camels and donkeys, and even men, women, and children, for a whole encampment of Arabs was washed away a few miles above me.^ One area of the river that was interesting paddling thru was down near where the South Fork narrowed (on the map it's the area that is 19 feet deep).
    • Chicago River Paddling/Fishing 12 January 2010 5:52 UTC pages.ripco.net [Source type: FILTERED WITH BAYES]

    The storm commenced at five in the evening; at half-past nine the waters were rapidly subsiding, and it was evident that the flood had spent its force." (Comp. Mt 7:27; Lk 6:49.)
  3. Nahar, a "river" continuous and full, a perennial stream, as the Jordan, the Euphrates (Gen 2:10; 15:18; Deut 1:7; Ps 666; Ezek 10:15).
  4. Tel'alah, a conduit, or water-course (1 Kg 18:32; 2Kg 18:17; 20:20; Job 38:25; Ezek 31:4).
  5. Peleg, properly "waters divided", i.e., streams divided, throughout the land (Ps 13); "the rivers [i.e., 'divisions'] of waters" (Job 20:17; 29:6; Prov 5:16).
  6. Ye'or, i.e., "great river", probably from an Egyptian word (Aur), commonly applied to the Nile (Gen 41:1-3), but also to other rivers (Job 28:10; Isa 33:21).
  7. Yubhal, "a river" (Jer 17:8), a full flowing stream.
  8. 'Ubhal, "a river" (Dan 8:2).
This entry includes text from Easton's Bible Dictionary, 1897.
what mentions this? (please help by turning references to this page into wiki links)

Simple English

File:River Thames - Isle of Dogs to
The River Thames in London, England. People have lived along the banks of this river for thousands of years.

A river is a stream of water that flows through a "channel" (or passage) in the surface of the ground. The passage where the river flows is called the riverbed and the earth on each side is called a riverbank. A river begins on high ground or in hills or mountains and flows down from the high ground to the lower ground, because of gravity. A river begins as a small stream and gets bigger, the farther that it flows.

The water in a river is called "fresh water". It comes from rain or snow and it can usually be drunk safely, unless it has been polluted. The water in a sea cannot be drunk safely because it is "salt water". Both people and animals often live near rivers, because they need water to survive.

Contents

About rivers

The beginning of a river

The beginning of a river is called its "source" or its "headwaters". The part of the river that is near the source is called a "young" or "youthful river".[1] A young river is often in a V-shaped river bed, and flows quickly downhill over stones, and around big rocks. Young rivers often have lots of small waterfalls and rapids.

  • The source of a river may be a spring, often on a hill, mountain, or another high place. A spring is water that flows out from under the ground.
  • The source of a river may be a lake where lots of water from small streams gathers when it rains or snows.
  • A river may begin in mountains where there is snow. The melting snow runs together to form a small stream that runs down the mountain. As more little streams run in, the main stream gets bigger, until it forms a river.
  • Some rivers flow from hills where there is no snow, but lots of rain.
  • Some rivers only flow after there has been rain at the "headwaters".

The middle part of a river

The middle part of a river is called a "mature river". A mature river makes a riverbed that is U-shaped. It might be very deep and run fast. It sweeps over small rocks and boulders, and makes big turns around hills and mountains. It is much wider than a "young river", but not as wide as an "old river". To cross over a mature river, people use bridges. Many cities and towns are built on the banks of mature rivers. Many farms that keep animals such as dairy cows, horses and sheep are found along mature rivers because the animals can drink from the river every day.

The last part of a river

A river usually ends by flowing into an ocean, a lake or a bigger river. The place where the river flows out into a bigger body of water is called the "mouth" of the river.

As a river flows towards its mouth, the countryside around the river often changes from hilly to flat. As it flows over the flat land the river becomes wider and slower. A wide slow river is called an "old river". An "old river" often floods across the land after there is lots of rain at the "headwaters". An "old river" slowly builds up its banks on either side; the high banks are called "levees". An old river often "meanders" (twists and turns), and sometimes, after a flood, it leaves lakes behind which are called "ox-bows" or "billabongs". Old rivers are the most useful type of river for growing crops. Corn, rice, fruit, cotton, hay, tobacco and sugar are some of the crops that are grown near old rivers.

The shape of the mouth depends on the conditions of the sea where it flows. If there is a strong tide where the river meets the sea, the river forms an estuary. An estuary is a wide, funnel-like mouth of the river. The fresh water of the river mixes slowly with the salt water, becoming brackish water - a "break" between fresh and salty water. Many kinds of fish, clams, mollusks and other sealife live at estuaries. Many of the world's largest cities and harbours are located at estuaries.

Where a river flows out to the sea, it sometimes flows very slowly through sandy or muddy land, making lots of little islands as it flows. The main stream of the river gets broken into many parts that spread out into a triangle shape like the Greek letter "Delta". When this happens, it is called the "delta" of the river. Deltas are often places that are not good for towns or farms but are very good for birds and other wildlife and fishing. Deltas are often made into wildlife reserves. Not all rivers have deltas. There are famous deltas on the Nile River, the Amazon River, the Mekong River, the Mississippi River and the Danube River.

Underground rivers

Some rivers flow underground through caves. Underground rivers form in places where there are lots of cracks in the rocks above, so that in rainy weather, the water runs downs and collects in small underground streams. Sometimes the underground water trickles or gushes out of the ground to form a small "spring" of water. In other places, where there are caves, the small underground streams run together to form a river. The river can sometimes run through deep wide underground caverns. While many underground rivers flow gently, some underground rivers flow fast and have rapids, particularly after heavy rain. Many underground rivers flow out through a cave mouth to become an ordinary river.

Using rivers

The water in rivers is "fresh water" that has come from rain, snow and from underground streams. It can usually be drunk safely by people unless it is too dirty because of mud or human pollution. People and animals need fresh water to drink, so they often live by the side of a river.

  • Rivers give water for drinking, bathing and washing clothes.
  • Rivers give water for cattle and other animals to drink and for people to grow plants.
  • Rivers give products that are useful to people such as fish for food, clay for bricks and reeds to make the roofs of houses.
  • Rivers can be used for transporting people, crops and other goods by boat.
  • Rivers can be used to give power to turn machinery such as water mills.
  • Rivers give water for factories that make cloth, steel and many other products.
  • Rivers sometimes have dams to hold the water for people to drink, or to make electricity.
  • Rivers can be used for leisure and sports such as swimming, boating, fishing and just walking by the river.
  • Rivers often have beautiful scenery. Many painters, story-tellers and poets have painted or written about rivers.

Water for living

Water for industry

Water for fun

Rivers in art, literature and music

  • Mark Twain, The Adventures of Tom Sawyer, (novel)
  • Kenneth Grahame, The Wind in the Willows, (novel)

Rivers in photography

Important rivers

Other types of rivers

  • A submarine river is a stream of water that flows along under the surface of an ocean. One of them, named the Cromwell current, was found in 1952. ("Sub marine" means "under sea".)
  • A subterranean river is a river which flows under the surface of the earth. One of them was found in August 1958 under the Nile River. ("Sub terranean" means "under ground".)

Other pages

References


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Citable sentences

Up to date as of December 16, 2010

Here are sentences from other pages on River, which are similar to those in the above article.








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