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{{अनुवाद}}
[[Image:Alter Strom.jpg|thumb|The Alten Strom, in the sea resort of [[Warnemünde]]]]
[[Image:IMG RoyalCanalnrKinnegad5706w.jpg|thumb|The [[Royal Canal]] in Ireland]]
'''Canals''' are artificial channels for water. There are two types of canals: [[Aqueduct|water conveyance]] canals, which are used for the conveyance and delivery of water, and [[waterways]], which are [[navigable]] [[transport]]ation canals used for passage of goods and people, often connected to existing [[lake]]s, [[river]]s, or [[ocean]]s. For canals used for water supply, see [[Aqueduct]].
==Types of artificial waterways==
Some canals are part of an existing waterway. This is usually where a river has been [[River engineering#Canalization of Rivers|canalised]]: making it navigable by widening and deepening some parts (by dredging and/or weirs), and providing locks with "cuts" around the [[weir]]s or other difficult sections. In France, these are called ''lateral canals'' and in the UK they are generally called [[navigation]]s, and the length of the artificial waterway often exceeds the natural. Smaller transportation canals can carry [[barge]]s or [[narrowboat]]s, while [[ship canal]]s allow seagoing [[ship]]s to travel to an inland port (eg [[Manchester Ship Canal]], or from one sea or ocean to another (eg [[Caledonian Canal]], [[Kiel Canal]]).
==Features==
[[Image:caen.hill.locks.in.devizes.arp.jpg|thumb|left|The flight of 16 consecutive locks at [[Caen Hill Locks|Caen Hill]] on the [[Kennet and Avon Canal]], [[Wiltshire]], [[England]]]]
[[Image:pontcysyllte aqueduct arp.jpg|thumb|left|A canal boat traverses the longest and highest aqueduct in the [[United Kingdom|UK]], at [[Pontcysyllte Aqueduct|Pontcysyllte]] in [[Denbighshire]], [[Wales]]]]
At their simplest, canals consist of a trench filled with water. Depending on the [[stratum]] the canal passes through, it may be necessary to line the cut with some form of watertight material such as clay or concrete. When this is done with clay this is known as [[Puddling (engineering)|puddling]].
Canals need to be flat, and while small irregularities in the lie of the land can be dealt with through cuttings and embankments for larger deviations, other approaches have been adopted. The most common is the pound [[canal lock|lock]] which consists of a chamber within which the water level can be raised or lowered connecting either two pieces of canal at a different level or the canal with a river or the sea. When there is a hill to be climbed, flights of many locks in short succession may be used.
Prior to the development of the pound lock in 984AD in China by Chhaio Wei-Yo<ref>{{Harvnb|Hadfield|1986|p=22.}}</ref> and later in Europe in the 15th century, either [[Canal lock#Flash locks|flash lock]]s consisting of a single gate were used, or ramps, sometimes equipped with rollers, were used to change level. Flash locks were only practical where there was plenty of water available.
Locks use a lot of water, so builders have adopted other approaches. These include [[boat lift]]s, such as the [[Falkirk wheel]], which use a [[Caisson (water transport)|caisson]] of water in which boats float while being moved between two levels; and [[canal inclined plane|inclined plane]]s where a caisson is hauled up a steep railway.
To cross a stream or road, the solution is usually to bridge with an [[aqueduct]]. To cross a wide valley (where the journey delay caused by a flight of locks at either side would be unacceptable) the centre of the valley can be spanned by an [[aqueduct]] - a famous example in Wales is the [[Pontcysyllte]] aqueduct across the valley of the River [[Dee]].
Another option when dealing with hills is to tunnel through them. An example of this approach is the [[Harecastle Tunnel]] on the [[Trent and Mersey Canal]]. Tunnels are only practical for smaller canals.
Some canals attempted to keep changes in level down to a minimum. These canals known as [[contour canal]]s would take longer winding routes, along which the land was a uniform altitude. Other generally latter canals took more direct routes requiring the use of various methods to deal with the change in level.
Canals have various features to tackle the problem of water supply. In some cases such as the Suez Canal the canal is simply open to the sea. Where the canal is not at sea level a number of approaches have been adopted. Taking water from existing rivers or springs was an option in some cases, sometimes supplemented by other methods to deal with seasonal variations in flow. Where such sources were unavailable, [[reservoirs]], either separate from the canal, or built into its course, and [[back pumping]] were used to provide the required water. In other cases water pumped from mines was used to feed the canal.
Where large amounts of good are loaded or unloaded such as the end of a canal a [[canal basin]] may be built. This would normally be a section of water wider than the general canal. In some cases the canal basin contain [[wharf]]s and cranes to assist with movement of goods.
==History==
===Ancient canals===
[[Image:Kaiserkanal01.jpg|thumb|right|The Grand Canal of China at Suzhou]]
The oldest known canals were built in [[Mesopotamia]] circa 4000 BC, in what is now modern day [[Iraq]] and [[Syria]]. The [[Indus Valley Civilization]] in [[Pakistan]] and [[North India]] (from circa 2600 BC) had a sophisticated canal [[irrigation]] system. Agriculture was practised on a large scale, and an extensive network of canals was used for the purpose of irrigation. Sophisticated irrigation and storage systems were developed, including the [[reservoir]]s built at [[Girnar]] in 3000 BC.<ref>{{Harvnb|Rodda|2004|p=161.}}</ref>
In [[Egypt]], canals date back at least to the time of [[Pepi I Meryre]] (reigned 2332 – 2283 BC), who ordered a canal built to bypass the [[Cataracts of the Nile|cataract]] on the Nile near [[Aswan]].<ref>{{Harvnb|Hadfield|1986|p=16.}}</ref>
In [[ancient China]], large canals for river transport were established as far back as the [[Warring States]] (481-221 BC), the longest one of that period being the Hong Gou (Canal of the Wild Geese), which according to the ancient [[historian]] [[Sima Qian]] connected the old states of Song, Zhang, Chen, Cai, Cao, and Wei.<ref>{{Harvnb|Needham|1971|p=269.}}</ref> By far the longest canal was the [[Grand Canal of China]], still the longest canal in the world today. It is {{convert|1794|km|mi}} long and was built to carry the [[Emperor Yang of Sui China|Emperor Yang Guang]] between [[Beijing]] and [[Hangzhou]]. The project began in 605 and was completed in 609, although much of the work combined older canals, the oldest section of the canal existing since at least 486 BC. Even in its narrowest urban sections it is rarely less than {{convert|30|m|ft}} wide.
===Canals in the Middle Ages===
The [[Naviglio Grande]] near [[Milan]] was the first artificial canal in Medieval Europe and the most important of the [[Lombardy|lombard]] “[[navigli]]”; started in [[1127]] and opened in [[1257]], allowing development of commerce, transport and agriculture.<ref>{{Harvnb|Calvert|1963|p=.}}</ref> Canal building was revived in this age because of commercial expansion from the 12th century AD. River navigations were improved progressively by the use of single, or [[flash lock]]s. Taking boats through these used large amounts of water leading to conflicts with [[watermill]] owners and to correct this, the [[Pound lock|pound]] or chamber lock first appeared, in 10th century AD in China and in Europe in 1373 in [[Vreeswijk]], Netherlands.<ref>{{Citation | title = The International Canal Monuments List | url = http://www.icomos.org/studies/canals.pdf | format = PDF | accessdate = 2008-10-08}}</ref> Another important development was the [[mitre gate]] which was probably introduced in Italy by Bertola da Novate in the sixteenth century. This allowed wider gates and also removed the height restriction of [[guillotine lock]]s.
To break out of the limitations caused by river valleys, the first [[summit level canal]]s were developed with the [[Grand Canal of China]] in 581-617 AD whilst in Europe the first, also using single locks, was the [[Stecknitz Canal]] in Germany in 1398. The first to use pound locks was the [[Briare Canal]] connecting the [[Loire]] and [[Seine]] catchment areas in France (1642) followed by the more ambitious [[Canal du Midi]] (1683) connecting the [[Atlantic]] to the [[Mediterranean]]. This included a staircase of 8 locks at Béziers, a {{convert|157|m|ft}} tunnel and three major [[aqueduct]]s.
Canal building progressed steadily in Germany in the 17th and 18th centuries with three great rivers, the [[Elbe]], [[Oder]] and [[Weser]] being linked by canals. In post-Roman Britain, the first canal built appears to have been the [[Exeter Canal]], which opened in 1563.
The oldest canal built for industrial purposes in North America is [[Mother Brook]] in [[Dedham, MA]]. It was constructed in 1639 to provide water power for mills. In [[Russia]], the [[Volga-Baltic Waterway]], a nationwide canal system connecting the [[Baltic Sea|Baltic]] and [[Caspian sea]]s via the [[Neva]] and [[Volga]] rivers, was opened in 1718.
The greatest stimulus to canal systems came from the [[Industrial Revolution]] with its need for cheap transport of raw materials and manufactured items.
===Industrial revolution===
[[Image:Canals USA 1825.png|thumb|right|US canals circa 1825]]
:{{see also|History of the British canal system}}
In Europe, particularly Britain and Ireland, and then in the young United States and the Canadian colonies, inland canals preceded the development of [[railroad]]s during the earliest phase of the [[Industrial Revolution]]. The opening of the [[Bridgewater Canal]] in 1761, which halved the price of coal in Manchester, triggered a period of "canal mania" in Britain so that between 1760 and 1820 over one hundred canals were built.
In the United States, navigable canals reached into isolated areas and brought them in touch with the world beyond. By 1825 the [[Erie Canal]], {{convert|363|mi|km}} long with 82 locks, opened up a connection from the populated Northeast to the fertile [[Great Plains]]. The [[Blackstone Canal]] in Massachusetts and Rhode Island fulfilled a similar role in the early industrial revolution between 1828-1848. The [[Blackstone Valley]] was considered the 'birthplace' of the American Industrial Revolution where Samuel Slater built his first mill.
In addition to their transportation purposes, parts of the United States, particularly in the [[Northeastern United States|Northeast]], had enough fast-flowing rivers that [[water power]] was the primary means of powering factories (usually textile mills) until after the [[American Civil War]]. For example, [[Lowell, Massachusetts]], considered to be "The Cradle of the American Industrial Revolution," has {{convert|6|mi|km}} of canals, built from around 1790 to 1850, that provided water power and a means of transportation for the city. The output of the system is estimated at 10,000 [[horsepower]]<ref>{{Citation | url = http://www.nps.gov/archive/lowe/loweweb/Lowell%20History/prologue.htm | title = Lowell National Historical Park - Lowell History Prologue | publisher = | accessdate = 2008-10-08}}</ref>. Other cities with extensive power canal systems include [[Lawrence, Massachusetts]], [[Holyoke, Massachusetts]], and [[Manchester, New Hampshire]].
{{-}}
===The 19th century===
Competition from the railway network from the 1830s, and later the roads, made the smaller canals obsolete for commercial transportation, and most of the British canals fell into decay. Only the [[Manchester Ship Canal]] and the [[Aire and Calder Canal]] bucked this trend. But in other countries canals grew in size as construction techniques improved. During the 19th century in the US, the length of canals grew from {{convert|100|mi|km}} to over 4,000, with a complex network making the [[Great Lakes]] navigable, in conjunction with [[Canada]], although some canals were later drained and used as railroad [[Right-of-way (railroad)|rights-of-way]].
In France, a steady linking of all the river systems—[[Rhine]], [[Rhône]], [[Saône]] and [[Seine]]—and the North Sea was boosted in 1879 by the establishment of the [[Freycinet gauge]] which specified the minimum size of locks so that canal traffic doubled in the first decades of the 20th century.<ref>{{Harvnb|Edwards|2002|p=.}}</ref>
Many notable sea canals were completed in this period, starting with the [[Suez Canal]] (1869), and the [[Kiel Canal]] (1897), which carries tonnage many times that of most other canals, though the [[Panama Canal]] was not opened until 1914.
In the 19th century, a number of canals were built in Japan including the [[Biwako canal]] and the [[Tone canal]]. These canals were partially built with the help of engineers from the Netherlands and other countries.<ref>{{Harvnb|Hadfield|1986|p=191.}}</ref>
===Modern uses===
Large scale ship canals such as the [[Panama Canal]] and [[Suez Canal]] continue to operate for cargo transportation; as do European barge canals. Due to [[globalization]], they are becoming increasingly important, resulting in expansion projects such as the [[Panama Canal expansion project]].
The narrow early industrial canals however have ceased to carry significant amounts of trade and many have been abandoned to navigation, but may still be used as a system for transportation of untreated water. In some cases railways have been built along the canal route, an example being the [[Croydon Canal]].
A movement that began in Britain and France to use the early industrial canals for pleasure boats has spurred rehabilitation of stretches of historic canals. In some cased abandoned canals such as the [[Kennet and Avon Canal]] have been restored and are now used by pleasure boaters. In Britain canalside housing has also proven popular in recent years.
The [[Seine-Nord Europe Canal]] is being developed into a major transportation waterway, linking [[France]] with [[Belgium]], [[Germany]] and the [[Netherlands]].
Canals have found another use in the 21st century, as [[wayleave]]s along the towing paths for [[fibre optic]] [[telecommunications]] networks.
==Cities on water==
[[Image:KeizersgrachtReguliersgrachtAmsterdam.jpg|thumb|left|An intersection of two canals in [[Amsterdam]], [[The Netherlands]].]]
Canals are so deeply identified with [[Venice]] that many canal cities have been nicknamed "the Venice of..." The city is built on marshy islands, with wooden piles supporting the buildings, so that the land is man-made rather than the waterways. The islands have a long history of settlement; by the 12th century, Venice was a powerful [[city state]].
[[Amsterdam]] was built in a similar way, with buildings on wooden piles. The pace of draining of [[fenland]] and [[polder]] in the [[Low Countries]] quickened in the 14th century and canalization made the village of Amsterdam a port. It became a city around 1300.
Other cities with extensive canal networks include: [[Brugge]] in [[Flanders]], [[Birmingham]] in [[England]], [[Saint Petersburg]] in [[Russia]], [[Hamburg]] in [[Germany]], and [[Fort Lauderdale, Florida]] in the [[United States]].
Canal estates are a form of [[Subdivision (land)|subdivision]] popular in cities like [[Miami, Florida]] and the [[Gold Coast, Queensland]]; the Gold Coast has over 700 km of residential canals. [[Wetlands]] are difficult areas upon which to build housing estates, so [[dredging]] part of the wetland down to a [[navigable]] channel provides fill to build up another part of the wetland above the flood level for houses. Land is built up in a finger pattern that provides a suburban street layout of waterfront housing blocks. This practice is not popular with [[environmentalists]].{{Fact|date=October 2008}}
{{-}}
==Boats==
[[Image:Panama Canal Miraflores Locks.jpg|thumb|right|Two [[Panamax]] in the [[Miraflores (Panama)|Miraflores Locks]] on the [[Panama Canal]]]]
Inland canals have often have had boats specifically built for them. An example of this is the British [[narrowboat]] which is up to {{convert|72|ft|m}} long and {{convert|7|ft|m}} wide and was primarily built for British Midland canals. In this case the limiting factor was the size of the locks. This is also the limiting factor on the Panama canal where [[Panamax]] boats are limited to a length of 294.1 metres and a width of 32.3 metres. For the lockless [[Suez Canal]] the limiting factor for [[Suezmax]]es is generally draft which is limited to 16 metres. At the other end of the scale, tub-boat canals such as the [[Bude Canal]] were limited to boats of under 10 tons for much of their length due to the capacity of their inclined planes or boat lifts. Most canals have a limit on height imposed either by bridges or tunnels.
{{-}}
==Gallery==
<gallery>
Image:Small canal - Venice.jpg|Rio della Verona: a ''rio'' or small canal in [[Venice]]
Image:Brugge-CanalRozenhoedkaai.JPG|[[Bruges]]
Image:Strépy-Braquegnies JPG003.jpg|[[Canal du Centre (Belgium)]]
Image:Pawtucket Canal Flood.jpg|The [[Pawtucket Canal]] during a flood of the [[Merrimack River]] at [[Lowell, Massachusetts|Lowell]], [[Massachusetts]]
Image:Canal_system_in_Lowell,_Massachusetts.jpg|Map of [[Lowell, Massachusetts|Lowell]]'s power canal system
Image:TucCanal.JPG|Irrigation canal outside [[Tucumcari, New Mexico]]
Image:Bridges over Canal, Amsterdam.JPG|Bridges over Canal, [[Amsterdam]]
Image:Calder and hebble.jpg|A stretch on the [[Calder and Hebble Navigation]], [[England]]
</gallery>
==Lists of Canals==
[[Image:Amsterdamcannel333.JPG|thumb|right|Amsterdam ''gracht'']]
*[[List of waterways]]
*'''Americas'''
**[[Canals of Canada]]
**[[List of canals in the United States]]
*'''Europe'''
**[[List of canals in France]]
**[[List of canals in Germany]]
**[[Canals of Ireland]]
**[[Canals of Great Britain]]
==See also==
* [[Barge]] (includes canal boats)
* [[Canal tunnel]]
* [[Channel (geography)|Channel]]
* [[Horse-drawn boat]]
* [[List of navigation authorities in the United Kingdom]]
* [[List of waterway societies in the United Kingdom]]
* [[Lock (water transport)|Lock]]
* [[Navigation authority]]
* [[Volumetric flow rate]]
* [[Water bridge]]
* [[Waterway restoration]]
* [[Water transportation]]
* [[Weigh lock]]
==Notes==
{{reflist}}
===Bibliography===
{{refbegin}}
*{{Citation | first = Roger | last = Calvert | title = Inland Waterways of Europe | publisher=George Allen and Unwin | year = 1963}}
*{{Citation | first = David | last = Edwards-May | title = European Waterways - map and concise directory | publisher = Euromapping | year = 2002}}
*{{Citation | first = Charles | last = Hadfield | authorlink = Charles Hadfield | title = World Canals: Inland Navigation Past and Present | publisher = David and Charles | year = 1986 | ISBN = 0-7153-8555-0}}
*{{Citation | first = J | last = Needham | title = Science and Civilisation in China | publisher = C.U.P. Cambridge | year = 1971}}
*{{Citation | first = J. C. | last = Rodda | title = The Basis of Civilization - Water Science? | publisher = International Association of Hydrological Sciences | year = 2004}}
{{refend}}
==External links==
{{Commonscat|canals}}
* [http://www.towpathtreks.co.uk/ Leeds Liverpool Canal Photographic Guide]
* [http://www.nycanals.com/ Information and Boater's Guide to the New York State Canal System]
* [http://academic.emporia.edu/aberjame/wetland/canal/canals.htm "Canals and Navigable Rivers" by James S. Aber, Emporia State University]
* [http://www.canals.org/ National Canal Museum (USA)]
* [http://www.world-city-photos.org/Amsterdam/photos/Canals_and_Bridges/ Canals in Amsterdam]
* [http://www.canaldumidi.com Canal du Midi]
* [http://www.canaldumidi.com/Canal-des-Deux-Mers.php Canal des Deux Mers]
* [http://www.usbr.gov/pmts/hydraulics_lab/water/bubbler/index.htm Canal flow measurement using a sensor].
[[Category:नहर| ]]
[[Category:Coastal construction]]
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