Aqueduct
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An aqueduct is an artificial channel that is constructed to convey water from one location to another. The word is derived from the Latin aqua, "water," and ducere, "to lead." The word is also used for any bridge that carries water, similar to viaducts, though they carry water instead of a road or railway. Sufficiently large aqueducts may also be usable by boats or ships. While a road bridge often carries the roadway at a more elevated level than the rest of the road, such a variation of height is not possible for an aqueduct.
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[edit] Ancient aqueducts
Although famously 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 limestone aqueduct 30 feet (10 m) high and 900 feet (300 m) long to carry water across a valley to their capital city, Nineveh. The full length of the aqueduct ran for 50 miles (80 km).
In the new world, the Aztec capital of Tenochtitlán was watered by two aqueducts in the middle of the second millennium.
[edit] Roman aqueducts
Roman aqueducts were built in all parts of the Roman Empire, from Germany to Africa, and especially in the city of Rome itself, where they totaled over 260 miles (416 km). The aqueducts were important for supplying water to large cities across the empire, and they set a high standard of engineering that was not surpassed for more than a thousand years. No mortar was needed to build these structures as the stones fit together so precisely.
[edit] Modern aqueducts
Much of the expertise of the Roman engineers was lost in the Dark Ages, and in Europe the construction of aqueducts largely ceased until the High Middle Ages. An example of an extant small scale aqueduct system built in 1202 by Cistercian monks is the Spanish Real Monasterio de Nuestra Señora de Rueda, whose central heating and waste disposal system relied upon a series of aqueducts originating from a diversion of the Ebro River. Through most of the Middle Ages and even up to the 19th century, water was instead usually supplied through the digging of wells, though this could cause serious public health problems when local water supplies became contaminated. One notable exception was the New River, a man-made waterway in England, opened in 1613 to supply London with fresh drinking water over a distance of 38 miles (62 km). The development of canals provided another spur to aqueduct building.
The 19th century saw aqueduct building resume on a large scale to supply fast-growing cities and water-hungry industries. The developments of new materials (such as cast iron) and new technologies (such as steam power) enabled significant improvements to be made. For instance, cast iron permitted the construction of larger, more highly pressurised inverted siphons, while steam- and electrically powered pumps enabled a major increase in the quantity and speed of water flow. England led the world in aqueduct construction, with notable examples being built to convey water to Birmingham, Liverpool and Manchester.
In modern times the largest aqueducts of all have been built in the United States to supply that country's biggest cities. The Catskill Aqueduct carries water to New York over a distance of 120 miles (190 km), but it 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 Delta to Lake Perris.
[edit] Uses of aqueducts
Historically, many agricultural societies have constructed aqueducts to irrigate crops. Archimedes invented the water screw to raise water for use in irrigation of croplands.
Another widespread use for aqueducts is to supply large cities with clean drinking water. Some of the famed 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, many aqueducts were constructed as part of the general 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. The aqueduct is a simple way to get water to other ends of a field.
In the past, aqueducts often had channels made of earth or other porous materials. 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.
[edit] Notable aqueducts
[edit] Ancient Greek aqueducts
- The Eupalinian aqueduct on the Greek island of Samos.
[edit] 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
See also: List of aqueducts in the Roman Empire
[edit] Other aqueducts
- Wignacourt Aqueduct, Malta. This aqueduct was 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 of this aqueduct 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 is 120 kilometers 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, 1350 miles of 17th century aqueducts on the Portuguese island of Madeira.
- Espada Aqueduct, built 1735, in San Antonio, Texas, United States.
- Quabbin Aqueduct, 24.6 miles long tunnel, in Massachusetts, United States.
- Chicopee Valley Aqueduct, 13.1 miles 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.
[edit] 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 18.3m 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 57m 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 307m. Other cast iron aqueducts followed such as the single span Stanley Ferry aqueduct on the Calder and Hebble Navigation in 1839 with its innovative 50m 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 2 substantial arch aqueducts on the higher stretches of the Loire, the longest being 470m 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 662m 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.
[edit] 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 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 234ft 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.
[edit] See also
- Aztec the Aztec Empire also used aqueducts
- Drought
- Flow
- Goldfields Water Supply Scheme
- Irrigation
- Leat
- Pipeline - some used to carry water
- Roman aqueduct
- Roman architecture
- Roman engineering
- Sanitation in Ancient Rome
- Viaduct - a similar structure to carry a road or a railway
- Water resources
[edit] References
- Sextus Julius Frontinus, De Aquaeductu Urbis Romae (On the water management of the city of Rome), Translated by R. H. Rodgers, 2003, University of Vermont
- Aqueduct entry from Encyclopædia Britannica Eleventh Edition
- Chanson, H. (2002). Certains Aspects de la Conception hydrauliques des Aqueducs Romains. ('Some Aspect on the Hydraulic Design of Roman Aqueducts.') Journal La Houille Blanche, No. 6/7, pp. 43-57 (ISSN 0018-6368)
- Chanson, H. (2008). "The Hydraulics of Roman Aqueducts: What do we know? Why should we learn ?" in Proceedings of World Environmental and Water Resources Congress 2008 Ahupua'a, ASCE-EWRI Education, Research and History Symposium, Hawaii, USA, Invited Keynote lecture, 13-16 May, R.W. BADCOCK Jr and R. WALTON Eds., 16 pages (ISBN-13: 978-0-7844-0976-3)
[edit] External links
