River 25510 225836316 2008-07-15T16:58:41Z Xenocidic 1795359 Reverted to revision 224603771 by [[Special:Contributions/Dysmorodrepanis|Dysmorodrepanis]]; restore prev good version. {{otheruses2|River}} :''"Riverine" redirects here. For the use of that term in [[maritime geography]], see there.'' [[Image:Colour patch near Blackwood mouth.jpg|thumb|[[Blackwood River]], [[Western Australia]]]] [[Image:MariaValeriaBridge.jpg|thumb|This bridge across the [[Danube River]] links [[Hungary]] with [[Slovakia]].]] [[Image:Homeward bound.jpg|thumb|A view across the [[Brahmaputra River|Brahmaputra]] from near Sukleswar ghat in [[Guwahati]].]] A '''river''' is a natural [[stream]] of [[water]], usually [[freshwater]], flowing toward an [[ocean]], a [[lake]], or another stream. In some cases a river flows into the ground or dries up completely before reaching another body of water. Usually larger streams are called rivers while smaller streams are called creeks, brooks, rivulets, rills, and many other terms, but there is no general rule that defines what can be called a river. Sometimes a river is said to be larger than a creek,<ref>[http://wordnet.princeton.edu/perl/webwn?s=river&sub=Search+WordNet&o2=&o0=1&o7=&o5=&o1=1&o6=&o4=&o3=&h= River], Wordnet</ref> but this is not always the case.<ref>[http://geonames.usgs.gov/domestic/faqs.htm USGS - U.S. Geological Survey - faqs], #17 What is the difference between [[mountain]], [[hill]], and [[peak]]; [[lake]] and [[pond]]; or [[river]] and [[creek]]?</ref> A river is a component of the [[water cycle]]. The water within a river is generally collected from [[Precipitation (meteorology)|precipitation]] through [[surface runoff]], [[groundwater]] recharge (as seen at baseflow conditions / during periods of lack of precipitation) and release of stored water in natural reservoirs, such as a [[glacier]]. ==Origins== [[Image:Tambo river.jpg|thumb|The youthful [[Tambo River (Victoria)|Tambo River]] flowing over a slight change in topography]] [[Image:ReichenbachBegin2.jpg|thumb|The beginning of a mountain river in the [[Swiss Alps]] (Reichenbach in [[Grosse Scheidegg]])]] A river may have its [[Source (river or stream)|source]] in a [[spring (hydrosphere)|spring]], lake, from damp, [[bog]]gy landscapes where the [[soil]] is [[waterlogged]], from glacial melt, or from surface runoff of precipitation. Almost all rivers are joined by other rivers and streams termed [[tributary|tributaries]], the highest of which are known as headwaters. Water may also originate from groundwater sources. Throughout the course of the river, the total volume 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 [[hyporheic zone|underlie the river and its floodplain]]. For many rivers in large valleys, this unseen component of flow may greatly exceed the visible flow. From their source, rivers flow downhill, typically terminating in a [[sea]] or in a lake, through a [[Confluence (geography)|confluence]]. In [[arid]] areas rivers sometimes end by losing water to [[evaporation]]. River water may also [[Infiltration (hydrology)|infiltrate]] into the soil or [[pervious]] rock, where it becomes groundwater. Excessive [[Water abstraction|abstraction]] of water for use in industry, irrigation, etc., can also cause a river to dry before reaching its natural terminus. The mouth, or lower end, of a river is known as its [[base level]]. The area drained by a river and its canals is called catchment, catchment basin, [[drainage basin]] or watershed. The term "watershed" is also used to mean a boundary between catchments, which is also called a [[water divide]], or in some, [[continental divide]]. ==Topography== [[Image:Mouths of amazon geocover 1990.png|thumb|left|[[Amazon River]] in [[Brazil]]]] The water in a river is usually confined to a [[channel (geography)|channel]], made up of a [[stream bed]] between [[stream bank|bank]]s. 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, is referred to as the beginning or source of the river flow regardless of the direction of flow. Therefore, the term down river, is referring to the direction of flow that the river continues in. The river channel typically contains a single stream of water, but some rivers flow as several interconnecting streams of water, producing a [[braided river]]. Extensive braided rivers are found in only a few regions worldwide, such as the [[South Island]] of [[New Zealand]]. They also occur on [[peneplain]]s 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. 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.<ref>{{cite book | last = Garde | first = R. J. | title = History of fluvial hydraulics | publisher = New Age Publishers | year = 1995 | url=http://books.google.com/books?lr=&hl=en&q=%22It+may+also+be+mentioned+that+criterion+for+the+beginning%22|pages=p. 19| isbn = 812240815X }}</ref> 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, [[meander]]s may form through erosion of the river banks and deposition on the inside of bends. Sometimes the river will cut off a loop, shortening the channel and forming an [[oxbow lake]] or [[billabong]]. Rivers that carry large amounts of [[sediment]] may develop conspicuous [[river delta|delta]]s at their mouths, if conditions permit. Rivers whose mouths are in saline [[tide|tidal]] waters may form [[estuary|estuaries]]. ==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. [[Image:river avon at keynsham arp.jpg|thumb|right|Leisure activities on the [[River Avon (Bristol)|River Avon]] at Avon Valley Country Park, [[Keynsham]], [[Bristol]], [[England]]. A boat giving trips to the public passes a moored private boat.]] ;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 (California)|Trinity River]], [[Ebro River]]) ;Mature river: a river with a gradient that is less steep than those of youthful rivers and flows more slowly than youthful rivers. 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 [[tectonics|tectonic]] uplift. The straight-line distance from the beginning to the end of most rivers is about one third their actual length.<ref>Hans-Henrik Stølum: "River Meandering as a Self-Organization Process", ''Science'' 271 (5256), 1710</ref><ref>Fermat's last theorem, Simon Singh, 1997</ref> The way 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 river]]s flow underground in [[cave]]s or caverns. Such rivers can be found in [[remote]] regions like Antarctica with [[limestone]] [[geologic formation]]s. 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 due to geologic conditions such as having a highly permeable river bed. ==Uses== Rivers have been used as a source of water, for food, for [[navigation|transport]], as a defensive barrier, as a source of [[hydroelctricity|power]] to drive machinery, and as a means of disposing of waste. For thousands of years rivers have been used for navigation (The earliest evidence of navigation is found in the [[Indus Valley Civilization]], which existed in northwestern [[India]] around 3300 BC). Riverine navigation provides the cheapest means of transport and is still used extensively on major rivers of the world like the [[Ganges River|Ganges]], the [[Nile]], the [[Mississippi River|Mississippi]], and the [[River Indus|Indus]]. In some heavily-forested regions like [[Scandinavia]] and [[Canada]], [[lumberjack]]s 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. Apart from being a rich source of [[fish]], rivers indirectly aid cultivation by supplying water for the crops. Rivers sustain their own [[food chain]]. They are a major source of fresh water, hence, it is no surprise to find most of the major [[city|cities]] of the world situated on the banks of rivers. Rivers help to determine the [[urban design|urban form]] of cities and neighbourhoods and their corridors often present opportunities for [[urban renewal]] through the development of [[foreshoreway]]s such as [[Riverwalk]]s. Rivers also provide an easy means of disposing of waste. [[Image:Hanami party, sakura and koi nobori.jpg|left|thumb|Most riverbanks in Japan are used as places for playing, recreation and parties]] The rocks and gravel generated and moved by rivers are used in construction. The beauty of rivers and their surroundings contributes to tourist income. In upland rivers, [[rapid]]s with [[whitewater]] or even [[waterfall]]s occur. Rapids are often used for recreational purposes, such as [[whitewater kayaking]]. Fast flowing rivers and waterfalls are harnessed as sources of energy, via [[watermill]]s and [[hydroelectric plant]]s. Rivers have been important in determining political boundaries and defending countries. For example, the [[Danube]] was a longstanding 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 River|Orange]] and [[Limpopo River|Limpopo]] Rivers in southern [[Africa]] form the boundaries between provinces and countries along their routes. [[Ancient Greece|Ancient Greek]] historian [[Megasthenes]] mentions about [[Ganges River|River Ganga]] several times in his work Indika: ''"India, again, possesses many rivers both large and navigable, which, having their sources in the mountains which stretch along the northern frontier, traverse the level country, and not a few of these, after uniting with each other, fall into the river called the Ganges. Now this river, which at its source is 30 [[stadia]] broad, flows from north to south, and empties its waters into the ocean forming the eastern boundary of the Gangaridai, a nation which possesses a vast force of the largest-sized elephants."'' (Diodorus II.37.) ==Biology== {{main|Aquatic 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. ==Flooding== [[Flood]]ing 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 [[floodplain]]s occur during flood stage. Human activity, however, has upset the natural way flooding occurs by walling off rivers, straightening their courses and by draining of natural [[wetland]]s. == Flow == ===Direction=== [[Image:RiverMeanderingCourse.jpg|right|]] Some people think that most rivers flow from north to south.<ref>{{cite web|title=Children's Misconceptions about Science|publisher=Operation Physics, American Institute of Physics|date=September 1998|url=http://amasci.com/miscon/opphys.html}}</ref><ref>{{cite web|title=Earth Science Misconceptions|author=William C. Philips|date=February 1991|url=http://k12s.phast.umass.edu/~nasa/misconceptions.html}}</ref> Rivers in fact flow downhill regardless of direction, often in a complex [[meander]]ing path involving all directions of the compass.<ref>{{cite web|author=Matt Rosenberg|title=Do All Rivers Flow South?|date=[[2006-06-08]]|url=http://geography.about.com/b/a/257582.htm}}</ref><ref>{{cite web|title=Rivers Flowing North: Rivers Only Flow Downhill; Rivers Do Not Prefer to Flow South|author=Matt Rosenberg|url=http://geography.about.com/od/learnabouttheearth/a/northrivers.htm}}</ref><ref>{{cite web|title=Re: What determines the direction of river flow? Elevation, Topography, Gravity??|work=Earth Sciences|author=Nezette Rydell|date=[[1997-03-16]]|url=http://www.madsci.org/posts/archives/mar97/858609276.Es.r.html}}</ref> Few major rivers in the continental U.S. flow north since most of the country is located in the watershed of the [[Pacific Ocean|Pacific]] or [[Atlantic Ocean|Atlantic]] oceans or the [[Gulf of Mexico]], with very few rivers flowing northward toward the [[Arctic Ocean]], [[Great Lakes]], or [[Hudson Bay]]. However, thousands of north-flowing rivers exist elsewhere, including such major watercourses as the [[Nile]], [[Mackenzie River|Mackenzie]], [[Rhine]], [[Yenisei]], [[Nelson River|Nelson]], and [[Lena River|Lena]]. Four of the ten [[List of rivers by length|longest river systems of the world]] flow mainly north. === Rate === [[Volumetric flow rate]], also called volume flow rate and rate of water flow, is the volume of water which passes through a given volume per unit time, measured in [[cubic meters per second]] (1 m³/s = 35.51 ft³/s) or [[cubic feet per second]], sometimes [[gallon]]s per second. == Management == {{main|River engineering}} Rivers are often managed or controlled to make them more useful, or less disruptive, to human activity. *[[Dam]]s or [[weir]]s may be built to control the flow, store water, or extract energy. *[[Levee]]s, known as dikes in Europe, may be built to prevent river water from flowing on floodplains or floodways. *[[Canal]]s 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. ==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> Image:Río Peralonso 2.jpg| Río Peralonso - [[El Zulia]] ([[Norte de Santander]]), [[Colombia]] Image:River_gambia_Niokolokoba_National_Park.gif| [[River Gambia]] flowing through Niokolokoba National Park Image:Howrah Bridge 01.jpg| [[Bridge]]s are a common way of crossing rivers ([[Hooghly River]], [[Kolkata]], [[India]]) Image:Victoria5.jpg| [[Zambezi]] and [[Victoria Falls]] ([[Zambia]]/[[Zimbabwe]], Africa) Image:Hooghly River 02.jpg| [[Hooghly River]] ([[Kolkata]], [[India]]) Image:Chosen5.JPG|[[Heathcote National Park]] Image:Chosen4.JPG|This river flows from [[Woronora Dam]], Sydney. </gallery> ==See also== {{seealso|geography|water cycle|drainage basin}} {{wiktionary}} {{Commons|River}} *[[Aqueduct]] *[[Baer's law]] *[[Canal]] *[[Drought]] *[[Hydrology]] *[[List of river name etymologies]] *[[List of rivers by average discharge]] *[[List of rivers by length]] *[[List of rivers of Africa]] *[[List of rivers of Asia]] *[[List of rivers of Europe]] *[[List of rivers of Oceania]] *[[List of rivers of the Americas]] *[[List of waterways]] *[[Mainstem (hydrology)]] *[[River cruise]] *[[Rock-cut basin]] *[[Water dispute]] ===Crossings=== *[[Bridge]]s *[[Ferry|Ferries]] *[[Ford (crossing)|Fords]] *[[Tunnel]]s ===Transport=== * [[Barge]] * [[Riverboat]] * [[Sailing]] * [[Towpath]] == References == <references /> ==Further reading== *Beyond the Bridges Life on American Rivers told by Riverlorian, Jerry Hay. [http://www.indianawaterways.com]for more information * {{cite encyclopedia|encyclopedia=Water Encyclopaedia|article=Rivers, Major World|author=Jeffrey W. Jacobs|url=http://www.waterencyclopedia.com/Re-St/Rivers-Major-World.html}} *{{cite book|authorlink=Luna Leopold|author=Luna B. Leopold|title=A View of the River|publisher=Harvard University Press|date=1994|id=ISBN}} &mdash; a non-technical primer on the [[geomorphology]] and [[hydraulics]] of water.......................=] =] =] [[Category:Rivers| ]] {{Link FA|he}} [[ar:نهر]] [[an:Río]] [[arc:ܢܗܪܐ]] [[ast:Ríu]] [[gn:Ysyry]] [[ay:Jawira]] [[zh-min-nan:Khe]] [[be:Рака]] [[be-x-old:Рака]] [[bar:Fluss]] [[bs:Rijeka (vodotok)]] [[br:Stêr]] [[bg:Река]] [[ca:Riu]] [[cv:Юханшыв]] [[cs:Řeka]] [[cy:Afon]] [[da:Flod]] [[pdc:Rewwer]] [[de:Fluss]] [[et:Jõgi]] [[el:Ποταμός]] [[eml:Fiòmm]] [[myv:Лей]] [[es:Río]] [[eo:Rivero]] [[eu:Ibai]] [[fa:رود]] [[fr:Rivière]] [[fur:Flum]] [[gd:Abhainn]] [[gl:Río]] [[ko:강]] [[hi:नदी]] [[hr:Rijeka (vodotok)]] [[id:Sungai]] [[is:Á (landform)]] [[it:Fiume]] [[he:נהר]] [[kk:Өзен]] [[sw:Mto]] [[kg:Mubu]] [[ht:Rivyè]] [[ku:Çem]] [[la:Flumen]] [[lv:Upe]] [[lb:Floss]] [[lt:Upė]] [[jbo:rirxe]] [[hu:Folyó]] [[mk:Река]] [[ml:നദി]] [[ms:Sungai]] [[mn:Гол]] [[nah:Ātōyātl]] [[nl:Rivier]] [[cr:ᓰᐲ]] [[ja:川]] [[nap:Sciummo]] [[no:Elv]] [[nn:Elv]] [[nrm:Riviéthe]] [[oc:Riu]] [[nds:Stroom (Water)]] [[pl:Rzeka]] [[pt:Rio]] [[ro:Râu]] [[qu:Mayu]] [[ru:Река]] [[sq:Lumi]] [[simple:River]] [[sk:Rieka]] [[sl:Reka]] [[szl:Řyka]] [[so:Webiyada]] [[sr:Река]] [[sh:Rijeka (vodotok)]] [[fi:Joki]] [[sv:Flod]] [[tl:Ilog]] [[ta:ஆறு]] [[th:แม่น้ำ]] [[vi:Sông]] [[tr:Nehir]] [[uk:Ріка]] [[vec:Fiume]] [[yi:טייך]] [[yo:Odò]] [[zh-yue:河]] [[bat-smg:Opė]] [[zh:河流]]