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Канал - Тази статия е за изкуствените водни пътища. За телевизионния канал вижте телевизия. За други значения вижте Канал (пояснение). Каналите са изкуствени водни пътища, обикновено свързващи съществуващи езера, реки или морета. Напоителните и отводнителни канали са предназначени за транспортиране на вода и исторически предшестват плавателните канали, използвани от кораби и други плавателни съдове. Най-старите известни канали са строени в Месопотамия около 4000 пр.н.е. Големият китайски канал е най-големият канал в Древността. След 14 век мрежата от канали отводнява големи райони в Нидерландия. В началото на Индустриалната революция каналите са важно средство за транспорт преди развитието на железниците. Конкуренцията на железопътната мрежа прави каналите неудачни за масов транспорт и много от тях западат. Съвременна тенденция в някои области на Западна Европа е живописни канали от зората на индустриализацията да се обновяват и да се използват за разходки с лодки. Друго приложение на каналите в наши дни е за полагане на оптични телекомуникационни кабели. [редактиране] Исторически сведения [редактиране] В древността Най-старите известни напоителни канали са изградени в Месопотамия около 4000 г.пр.н.е. По времето на Индската цивилизация в днешните Пакистан и Северна Индия в периода около 2600 г.пр.н.е. са изградени забележителни напоителни канали и водохранилища.[1] Сведения за първите канали са от около 2300 г.пр.н.е. при управлението на Мерира Пиопи I. Тогава е изграден страничен канал на Нил, който да заобиколи един от бързеите на реката близо до Асуан.[2] В древен Китай, плаването по междуречни канали е основано в периода 481–221 г.пр.н.е. като най-дългият известен канал от това време е Хонг Гоу (известен като Канала на дивата гъска). Той е описан и от древнокитайския историк Сима Циен като според описанията му е свързвал древните китайски държави Сонг, Джан, Чен, Кай, Цао и Вей.[3] Далеч по-дълъг е каналът наречен Велик китайски канал, който и днес продължава да е най-дългия канал в света. Той е дълъг 1794 km и е изграден от император Ян като транспортна връзка между Пекин и Ханджоу. Строежът му започва през 605 година и завършва през 609 г., като за прокарването му са използвани и стари напоителни канали съществували още преди стотици години като най-старият от тях е от 486 г.пр.н.е. В най-тесните си участъци преминаващи през населени места каналът е широк не по-малко от 30 метра. Древногръцките инженери първи използват шлюзове при строежите на канали, които да регулират водното течение. Първите опити за прилагането им са от древния египетски канал между Нил и Червено море.[4][5][6] [редактиране] В Средновековието През средните векове водният транспорт се превръща в евтин и бърз начин за извършване на търговия. Причината за това е, че пътищата са неподдържани и в твърде лошо състояние след краха на Римската империя, а посредством водния транспорт превозваните товари могат да бъдат и в по-голямо количество. Първият изкуствен канал в християнска Европа е Fossa Carolina, построен в края на 8 век под личното ръководство на Карл Велики. По-трайно и икономически по-ефективно се оказало изграждането на италианския канал Naviglio Grande, построен между 1127 - 1257 г.[7] По-късно са изградени и канали в Нидерландия и Фландрия с цел отводняване на полдерите и подобряване на търговията. Строежът на канали преживява нов подем през тази епоха поради бурното развитие на търговията през 12 век. Речното корабоплаване се подобрява рязко с въвеждането на една от най-простите системи за регулиране на нивото, наречена flash lock. Поради факта, че така се затруднявала работата на мелничарската промишленост се наложило да се коригират механизмите на пропускане на водата и била въведена нова система наречена Pound lock. Първата известна е от 10 век в Китай, а в Европа е въведена през 1373 във Vreeswijk, Нидерландия.[8] Друго важно развитие настъпва с откриването на съединяващи се под ъгъл шлюзове преграждащи течението. За първи път такива са изградени в Италия в Бертола да Новате през 16 век. Следващото нововъведение били шлюзовете тип Гилотина. Първият известн канал, който съединява речни долини отделени с хълмове е Великият китайски канал. В Европа първият подобен тип канал е от Германия изграден през 1398 година. Първият канал, който използва системата „pound lock“ съединява Лоара от Сена и е изграден през 1683 г., последван от Канал дьо Миди, свързващ Атлантически океан със Средиземно море. За да функционира правилно са изградени 8 шлюза, тунел, дълъг 157 метра и три големи акведукта. Строежът на канали напредва с постоянен темп в Германия през 17-ти и 18-ти век като се свързват трите големи реки, Елба, Одер и Везер. Във Великобритания вероятно първият построен канал е Ексетър, открит през 1563 година. Най-старият канал, построен за промишлени цели в Северна Америка е „Mother Brook“ в Дедам, Масачузетс. Той е изграден през 1639 г. с цел осигуряването на вода за задвижването на мелници. В Русия, Волго-Балтийския канал, е част от националната система от канали в страната. Пуснат е в експлоатация през 1718 г. и свързва Балтийско море с Каспийско, посредством връзката между реките Нева и Волга. [редактиране] Индустриална революция Каналите стават още по-важни с развитието на промишлеността. Най-големият стимул за изграждане на каналната система идва през Индустриалната революция с необходимостта от осигуряването на евтин транспорт на големи количества суровини и произведени стоки. В Европа, особено Великобритания и Ирландия, а по-късно и в нововъзникналите колонии в Северна Америка, изграждането на канали предшества развитието на железниците по време на ранната фаза на Индустриалната революция. След откриването на каналите „Санки“ (1757) и „Бриджуотър“ (1761) цената на въглищата в Ливърпул и Манчестър успява да падне наполовина. Това от своя страна е причината за манията да бъдат изграждани канали във Великобритания. В периода между 1760 и 1820 година в страната са открити над сто канала. Освен за нуждите на промишлеността, Кралския военен канал в Ромни Марш е изграден за да служи като бариера против нашественици и да осигури сигурна защита на бретанската армия по време на Наполеоновите войни.[9] Каналът „Блакстоун“ в Масачузетс и Роуд Айлънд изпълнява подобна роля в началото на Индустриалната революция в периода между 1828 –1848 г. Долината Блекстоун се превръща в голям износител на стоки по време на Американската индустриална революция. Като допълнение на транспортните цели на САЩ, части от страната, предимно на североизток, където има голям брой бързотечащи реки, водната енергия се превръща в основно средство за захранване с енергия на заводите (най-вече текстилни фабрики), особено в периода след Гражданската война в Америка. Като пример за това в Лоуъл, който се смята за „Люлката на американската индустриална революция“ са изградени 9,7 km канали, построени от 1790 до 1850 година.[10] [редактиране] Вижте още [редактиране] Източници - ↑ Hadfield 1986, с. 16. - ↑ Needham 1971, с. 269. - ↑ Moore, Frank Gardner (1950): "Three Canal Projects, Roman and Byzantine", American Journal of Archaeology, Vol. 54, No. 2, pp. 97–111 (99–101) - ↑ Froriep, Siegfried (1986): "Ein Wasserweg in Bithynien. Bemühungen der Römer, Byzantiner und Osmanen", Antike Welt, 2nd Special Edition, pp. 39–50 (46) - ↑ Schörner, Hadwiga (2000): "Künstliche Schiffahrtskanäle in der Antike. Der sogenannte antike Suez-Kanal", Skyllis, Vol. 3, No. 1, pp. 28–43 (33–35) - ↑ Calvert 1963, с. - ↑ (PDF) The International Canal Monuments List, http://www.icomos.org/studies/canals.pdf, посетен 2008-10-08 - ↑ History. // The Royal Military Canal, 1909-12-15. - ↑ Lowell National Historical Park — Lowell History Prologue, http://www.nps.gov/archive/lowe/loweweb/Lowell%20History/prologue.htm, посетен 2008-10-08
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नहर Canals are artificial channels for water. There are two types of canals: water conveyance canals, which are used for the conveyance and delivery of water, and waterways, which are navigable transportation canals used for passage of goods and people, often connected to existing lakes, rivers, or oceans. For canals used for water supply, see Aqueduct. धलः Types of artificial waterways[सम्पादन] Some canals are part of an existing waterway. This is usually where a river has been canalised: making it navigable by widening and deepening some parts (by dredging and/or weirs), and providing locks with "cuts" around the weirs or other difficult sections. In France, these are called lateral canals and in the UK they are generally called navigations, and the length of the artificial waterway often exceeds the natural. Smaller transportation canals can carry barges or narrowboats, while ship canals allow seagoing ships to travel to an inland port (eg Manchester Ship Canal, or from one sea or ocean to another (eg Caledonian Canal, Kiel Canal). Features[सम्पादन] 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. 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 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[१] and later in Europe in the 15th century, either flash locks 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 lifts, such as the Falkirk wheel, which use a caisson of water in which boats float while being moved between two levels; and inclined planes 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 canals 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 wharfs and cranes to assist with movement of goods. History[सम्पादन] Ancient canals[सम्पादन] 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 reservoirs built at Girnar in 3000 BC.[२] 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 cataract on the Nile near Aswan.[३] 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.[४] By far the longest canal was the Grand Canal of China, still the longest canal in the world today. It is १,७९४ kilometres (० mi) long and was built to carry the 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 ३० metres (० ft) wide. Canals in the Middle Ages[सम्पादन] The Naviglio Grande near Milan was the first artificial canal in Medieval Europe and the most important of the lombard “navigli”; started in 1127 and opened in 1257, allowing development of commerce, transport and agriculture.[५] 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 locks. Taking boats through these used large amounts of water leading to conflicts with watermill owners and to correct this, the pound or chamber lock first appeared, in 10th century AD in China and in Europe in 1373 in Vreeswijk, Netherlands.[६] 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 locks. To break out of the limitations caused by river valleys, the first summit level canals 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 १५७ metres (० ft) tunnel and three major aqueducts. 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 and Caspian seas 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[सम्पादन] - स्वयादिसँ: 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 railroads 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, ३६३ miles (० 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 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 ६ miles (९.७ 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[७]. Other cities with extensive power canal systems include Lawrence, Massachusetts, Holyoke, Massachusetts, and Manchester, New Hampshire. The 19th century[सम्पादन] 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 १०० miles (० 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 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.[८] 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.[९] Modern uses[सम्पादन] 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 wayleaves along the towing paths for fibre optic telecommunications networks. Cities on water[सम्पादन] 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 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.[पुष्टि(साइटेसन) मागु] Boats[सम्पादन] Inland canals have often have had boats specifically built for them. An example of this is the British narrowboat which is up to ७२ feet (० m) long and ७ feet (२.१ 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 Suezmaxes 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[सम्पादन] Small canal - Venice.jpg Rio della Verona: a rio or small canal in Venice The Pawtucket Canal during a flood of the Merrimack River at Lowell, Massachusetts Map of Lowell's power canal system TucCanal.JPG Irrigation canal outside Tucumcari, New Mexico Bridges over Canal, Amsterdam A stretch on the Calder and Hebble Navigation, England Lists of Canals[सम्पादन] - List of waterways - Americas - Europe See also[सम्पादन] - Barge (includes canal boats) - Canal tunnel - Channel - Horse-drawn boat - List of navigation authorities in the United Kingdom - List of waterway societies in the United Kingdom - Lock - Navigation authority - Volumetric flow rate - Water bridge - Waterway restoration - Water transportation - Weigh lock Notes[सम्पादन] - ↑ Hadfield 1986, p. 22. - ↑ Hadfield 1986, p. 16. - ↑ Needham 1971, p. 269. - ↑ Calvert 1963, p. - ↑ The International Canal Monuments List,  . Retrieved on ८ अक्टोबर २००८ - ↑ Lowell National Historical Park - Lowell History Prologue,  . Retrieved on ८ अक्टोबर २००८ - ↑ Edwards 2002, p. - ↑ Hadfield 1986, p. 191. Bibliography[सम्पादन] - Calvert, Roger (1963), Inland Waterways of Europe, George Allen and Unwin - Edwards-May, David (2002), European Waterways - map and concise directory, Euromapping - Hadfield, Charles (1986), World Canals: Inland Navigation Past and Present, David and Charles, ISBN 0-7153-8555-0 - Needham, J (1971), Science and Civilisation in China, C.U.P. Cambridge - Rodda, J. C. (2004), The Basis of Civilization - Water Science?, International Association of Hydrological Sciences External links[सम्पादन] - Leeds Liverpool Canal Photographic Guide - Information and Boater's Guide to the New York State Canal System - "Canals and Navigable Rivers" by James S. Aber, Emporia State University - National Canal Museum (USA) - Canals in Amsterdam - Canal du Midi - Canal des Deux Mers - Canal flow measurement using a sensor.