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Aqueduct
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, Portugal. It was built between 1593 and 1614, to serve the Convent of Christ ]]
An aqueduct is a water supply or navigable channel (conduit) constructed to convey water. In modern engineering, the term is used for any system of pipes, ditches, canals, tunnels, and other structures used for this purpose.
In a more restricted use, aqueduct (occasionally water bridge) applies to any bridge or viaduct that transports water —instead of a path, road or railway —across a gap.
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, Portugal. It was built between 1593 and 1614, to serve the Convent of Christ ]]
An aqueduct is a water supply or navigable channel (conduit) constructed to convey water. In modern engineering, the term is used for any system of pipes, ditches, canals, tunnels, and other structures used for this purpose.
In a more restricted use, aqueduct (occasionally water bridge) applies to any bridge or viaduct that transports water —instead of a path, road or railway —across a gap. Large navigable aqueducts are used as transport links for boats or ships. Aqueducts must span a crossing at the same level as the watercourses on each side (alternative solutions involving a change of water level are water pumps or siphons [for water transport], and Boat lift or Pound lock or Canal inclined plane [for boat movement]). The word is derived from the Latin ("water") and ("to lead").
Ancient aqueducts
Although particularly associated with the Romans, aqueducts were devised much earlier in the Near East and Indian subcontinent, where peoples such as the Egyptians and Harappans built sophisticated irrigation systems. Roman-style aqueducts were used as early as the 7th century BC, when the Assyrians built a 50 mile (80 km) long limestone aqueduct, 30 feet (10 m) high and 900 feet (300 m) wide, to carry water across a valley to their capital city, Nineveh.
In the new world, when the Aztec capital of Tenochtitlán was discovered in the middle of the second millennium, it was watered by two aqueducts.
India
The Indian subcontinent had some of the earliest aqueducts. Evidence can be found at the sites of present day Hampi. The massive aqueducts near river Tungabhadra supplying irrigation water were once long. The water ways supplied water to royal bath houses.
Persia
In Persia from early times a system of underground aqueducts called Qanat were constructed, a series of well-like vertical shafts, connected by gently sloping tunnels. This technique:
- taps into subterranean water in a manner that delivers water to the surface without need for pumping. The water drains relying on gravity, with the destination lower than the source, which is typically an upland aquifer.
- allows water to be transported long distances in hot dry climates without losing a large proportion of the source water to seepage and evaporation.
Roman
Roman aqueducts were built in all parts of the Roman Empire, from Germany to Africa, and especially in the city of Rome, where they totalled over 260 miles (416 km). The aqueducts supplied water to large cities across the empire, and set a standard of engineering that was not surpassed for more than a thousand years.
South America
Near the Peruvian town of Nazca, an ancient pre-columbian system of aqueducts called Puquios were built and are still in use today. They are made of intricately placed stones, a construction material widely used by the Nazca culture. The time period in which they were constructed is still debated, but some evidence supports circa A.D. 540-552, in response to drought periods in the region.
Modern aqueducts
In modern times, the largest aqueducts of all have been built in the United States to supply the country's biggest cities. The Catskill Aqueduct carries water to New York City over a distance of 120 miles (190 km), but is dwarfed by aqueducts in the far west of the country, most notably the Colorado River Aqueduct, which supplies the Los Angeles area with water from the Colorado River nearly 250 miles (400 km) to the east, and the 444 mile (714.5 km) California Aqueduct, which runs from the Sacramento-San Joaquin River Delta to Lake Perris.
Uses
Historically, agricultural societies have constructed aqueducts to irrigate crops. Archimedes invented the water screw to raise water for use in irrigation of croplands.
Another use for aqueducts is to supply large cities with drinking water. Some of the Roman aqueducts still supply water to Rome today. In California, USA, three large aqueducts supply water over hundreds of miles to the Los Angeles area. Two are from the Owens River area and a third is from the Colorado River.
In more recent times, aqueducts were used for transportation purposes to allow canal barges to cross ravines or valleys. During the Industrial Revolution of the 18th century, aqueducts were constructed as part of the boom in canal-building.
In modern civil engineering projects, detailed study and analysis of open channel flow is commonly required to support flood control, irrigation systems, and large water supply systems when an aqueduct rather than a pipeline is the preferred solution.
In the past, aqueducts often had channels made of earth or other porous materials but significant amounts of water are lost through such unlined aqueducts. As water gets increasingly scarce, these canals are being lined with concrete, polymers or impermeable soil. In some cases, a new aqueduct is built alongside the old one because it cannot be shut down during construction.
Notable aqueducts
Ancient Greek aqueducts
Roman aqueducts
*The Pont du Gard in southern France
- Barbegal aqueduct, France
- Eifel aqueduct, Germany
- Caesarea Maritima, Israel
- Kavala, Greece
- Patras, Greece
- Aqueduct of Segovia, Spain
- Acueducto de los Milagros, Mérida, Spain
- Tarragona, Spain
- Almuñécar, Spain (5 aqueducts - 4 still in use)
- Valens Aqueduct, Istanbul, Turkey
- Aqua Augusta, Italy
- Aqua Claudia and the Anio Novus, as part of the Porta Maggiore, Rome, Italy
- Skopje Aqueduct, Skopje, Republic of Macedonia
Other aqueducts
- Wignacourt Aqueduct, Malta. Built in the 16th century to transport water from the old capital city of Malta, Mdina to the new capital city Valletta. Today, only part is visible in the localities of Balzan, Birkirkara and Santa Venera.
- Aqueduct St-Clément, Montpellier, France - 17th century
- Águas Livres Aqueduct, in Lisbon, Portugal (built 1731-1748)
- Carioca Aqueduct in Rio de Janeiro, Brazil (built 1744-1750)
- Aqueduct of Teruel, Spain
- Roquefavour aqueduct, France - built between 1842 and 1847
- Winnipeg Aqueduct, Manitoba, Canada - built between 1915 and 1919
- Canal de l'Aqueduc, Quebec, Canada
- Päijänne Water Tunnel, a 120 kilometer long underground aqueduct (continuous tunnel) connecting lake Päijänne to Greater Helsinki.
- Wan Mat Saman Aqueduct, Kedah, Malaysia - built between 1900 and 1909
- Mathur Aqueduct in Tamilnadu state, India
- Surviving Spanish aqueducts in Mexico:
- Levadas, of 17th century aqueducts on the Portuguese island of Madeira.
- Espada Aqueduct, built 1735, in San Antonio, Texas, United States.
- Quabbin Aqueduct, long tunnel, in Massachusetts, United States.
- Chicopee Valley Aqueduct, long, in Massachusetts, United States.
- Central Arizona Project Aqueduct
- California Aqueduct, a 444 miles (approx. 714.5 kilometers) long combination of canals, pipelines and tunnels, United States.
- Delaware Aqueduct, in New York State, United States - at 85 miles (137 km) long, the world's longest continuous underground tunnel.
- High Bridge, part of the former Croton Aqueduct, built in 1848, is the oldest surviving bridge in New York City.
Navigable aqueducts
Navigable aqueducts are bridge structures which carry canals over other rivers, valleys or railways or roads. They are primarily distinguished by their size, carrying a larger cross-section of water than most water-supply aqueducts. Although Roman aqueducts were sometimes used for transport, aqueducts were not generally used until the 17th century when the problems of summit level canals had been solved and the modern canal system started to appear.
Early aqueducts such as the three on the Canal du Midi (1683) were stone or brick arches, the longest span being 18.3 m on the Cesse Aqueduct (1686). However the weight of the construction to support the trough with the clay or other lining to make it waterproof made these structures clumsy and it was not until 1796 that the first large cast iron aqueduct was built at Longdon-on-Tern by Thomas Telford on the Shrewsbury Canal. It has a total length of 57 m with 3 intermediate piers. Within 10 years he had completed the far more ambitious Pontcysyllte Aqueduct over the Dee valley on the Llangollen Canal which has a total length of 307 m. Other cast iron aqueducts followed such as the single span Stanley Ferry Aqueduct on the Calder and Hebble Navigation in 1839 with its innovative 50 m through arch design.
The impact of new materials can be seen in the experience of the Canal latéral à la Loire in France. It had two substantial arch aqueducts on the higher stretches of the Loire, the longest being 470 m completed in 1838, but a river-level crossing was used to cross the Loire to the Canal de Briare because the consequent obstruction to the river during flooding was considered unacceptable. This proved troublesome until the 662 m long steel Briare aqueduct was built in 1896, which remained the longest aqueduct in the world until the 21st century when the Magdeburg Water Bridge in Germany took the title.
Notable navigable aqueducts
- Benjamin Outram's 44ft-long single-span Holmes Aqueduct on the Derby Canal in Derby was the world's first navigable cast iron aqueduct, narrowly predating Thomas Telford's 186ft-long Longdon-on-Tern Aqueduct on the Shrewsbury Canal, sometimes described as the world's first large-scale navigable cast iron aqueduct.
- Chirk Aqueduct, Wales - built between 1796 and 1801
- Pontcysyllte Aqueduct carries the Llangollen Canal over the River Dee valley in north Wales, and was designed by Thomas Telford and opened in 1805. The same canal, which includes a tunnelled section crosses a second valley on the Chirk Aqueduct. This navigable canal also supplies water to the borough of Crewe and Nantwich.
- Union Canal in Scotland has many aqueducts, including the Slateford Aqueduct that takes the canal over the Water of Leith, the Almond Aqueduct over the River Almond at Ratho and the very impressive Avon Aqueduct over the River Avon. This is the second longest aqueduct in the United Kingdom.
- In recent years the building of the Lichfield Canal Aqueduct prompted the UK government to pass legislation preventing a road being built in the path of a canal being renovated without providing a tunnel or aqueduct for it to pass.
- Barton Swing Aqueduct - a form of swing bridge that carries the Bridgewater Canal across the lower Manchester Ship Canal. A section of the aqueduct rotates through 90 degrees to allow vessels to pass along the Ship Canal.
- Aqueduct near Roelofarendsveen, Netherlands (1961) : carries the Ringvaart canal over the A4 highway and the HSL Zuid being constructed, which are situated on land below the level of the canal (and below sea level)
- Gouwe aqueduct, near Gouda, Netherlands: carries the Gouwe river over the A12 highway, which is on land below the level of the river
- The Ash Aqueduct (1995) carries the Basingstoke Canal over the River Blackwater and Blackwater Valley Relief Road (A331).
- The Magdeburg Water Bridge in Germany (2003) connects the important Mittellandkanal over the river Elbe to the Elbe-Havel canal . Nearly 1 km long, it is the longest aqueduct in Europe.
See also
External links
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