Aqueduct (water supply)

The Central Arizona Project allows passage of water from the Colorado River to central and southern Arizona. At 336 miles (541 km), it is the largest aqueduct ever constructed in the United States.

An aqueduct is a watercourse constructed to convey water. In modern engineering, the term aqueduct is used for any system of pipes, ditches, canals, tunnels, and other structures used for this purpose. The term aqueduct also often refers specifically to a bridge on an artificial watercourse. The word is derived from the Latin aqua ("water") and ducere ("to lead"). Aqueducts were used in ancient Greece, ancient Egypt, and ancient Rome. In modern times, the largest aqueducts of all have been built in the United States to supply the country's biggest cities. The simplest aqueducts are small ditches cut into the earth. Much larger channels may be used in modern aqueducts. Aqueducts sometimes run for some or all of their path through tunnels constructed underground. Modern aqueducts may also use pipelines. Historically, agricultural societies have constructed aqueducts to irrigate crops and supply large cities with drinking water.

Ancient aqueducts

Further information: History of water supply and sanitation

Although particularly associated with the Romans, aqueducts were devised much earlier in Greece and 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 an 80 km long limestone aqueduct, which included a 10 m high section to cross a 300 m wide valley, to carry water to their capital city, Nineveh.

India

Ancient Indian aqueduct in Hampi

The Indian subcontinent is believed to have some of the earliest aqueducts. Evidence can be found at the sites of present-day Hampi, Karnataka. The massive aqueducts near river Tungabhadra supplying irrigation water were once 15 miles (24 km) long. The waterways supplied water to royal bath tubs.

Oman

Main article: Falaj

In Oman from the Iron Age, in Salut, Bat, and other sites, a system of underground aqueducts called falaj or qanāts were constructed, a series of well-like vertical shafts, connected by gently sloping horizontal tunnels.

There are three types of falaj:

• Daudi (داوودية) with underground aqueducts
• Ghaili (الغيلية ) requiring a dam to collect the water
• Aini (العينية ) whose source is a water spring

These enabled large scale agriculture to flourish in a dry land environment.

Persia

Main article: Qanat

In Persia from early times a system of underground aqueducts called qanāts 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.

Petra, Jordan

Nabataean aqueduct in Petra, Jordan

Throughout Petra, Jordan, the Nabataean engineers took advantage of every natural spring and every winter downpour to channel water where it was needed. They constructed aqueducts and piping systems that allowed water to flow across mountains, through gorges and into the temples, homes, and gardens of Petra's citizens. Walking through the Siq, one can easily spot the remains of channels that directed water to the city center, as well as durable retention dams that kept powerful flood waters at bay.

Greece

On the island of Samos, the Tunnel of Eupalinos was built during the reign of Polycrates (538-522 BC). It is considered an underground aqueduct and brought fresh water to Pythagoreion for roughly a thousand years.

Roman

The multiple arches of the Pont du Gard, in Roman Gaul. Its lower tiers carry a road across the river, and the upper tiers support an aqueduct conduit that carried water to Nimes

Main article: Roman aqueduct

Roman aqueducts were built in all parts of the Roman Empire, from Germany to Africa, and especially in the city of Rome, where they totaled over 415 km. The aqueducts supplied fresh water to public baths and for drinking water, in large cities across the empire, and set a standard of engineering that was not surpassed for more than a thousand years. Bridges, built in stone with multiple arches, were a distinctive feature of Roman aqueducts and hence the term aqueduct is often applied specifically to a bridge for carrying water.

South America

Underground aqueducts of Cantalloc, Nazca, Peru

Near the Peruvian town of Nazca, an ancient pre-Columbian system of aqueducts called Puquios were built and are still in use today. They were 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.

The Guayabo National Monument of Costa Rica, a park covering the largest archaeological site in the country, contains a system of aqueducts. The complex network of uncovered and covered aqueducts still functions well. The aqueducts are constructed from rounded river stones, which are mostly made of volcanic rock. The civilization that constructed the aqueduct system remains a mystery to archaeologists; it is suspected that Guayabo's aqueducts sat at a point of ancient cultural confluence between Aztecs, Mayans, and Incas.

North America

When Europeans saw the Aztec capital Tenochtitlán, early in the 16th century, the city was watered by two aqueducts. One of these, Chapultepec Aqueduct, built circa 1420, was rebuilt by the Spanish almost three hundred years later. Originally tracing part of its path over now-gone Lake Texcoco, only a fragment remains in Mexico City today.

Sri Lanka

Extensive usage of elaborate aqueducts have been found to have been used in ancient Sri Lanka.The best example is the Yoda Ela or Jaya Ganga, an 87 km long water canal carrying excess water between two artificial reservoirs with a gradient of 10 to 20 cm per kilometer during the fifth century AD. However, the ancient engineering methods in calculating the exact elevation between the two reservoirs and the exact gradient of the canal to such fine precision had been lost with the fall of the civilization in 13th Century.

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 400 km to the east and the 701.5 mi (1,129 km) California Aqueduct, which runs from the Sacramento-San Joaquin River Delta to Lake Perris. The Central Arizona Project is the largest and most expensive aqueduct constructed in the United States. It stretches 336 miles from its source near Parker, Arizona to the metropolitan areas of Phoenix and Tucson. An aqueduct in New Zealand, "the Oamaru Borough Race" was constructed in the late 19th century to deliver water (and water-power) about 50 km from the Waitaki River at Kurow to the coastal town of Oamaru.

In Spain, the Tagus-Segura Water Transfer system of aqueducts opened in 1979 and transports water 286 kilometres (178 mi) from north to south.

Design

Open channels

The simplest aqueducts are small ditches cut into the earth. Much larger channels may be used in modern aqueducts, for instance the Central Arizona Project uses 7.3 m (24 ft) wide channels. A major factor in the design of all open channels is its gradient. A higher gradient allows a smaller channel to carry the same amount of water as a larger channel with a lower gradient, but increases the potential of the water to damage the aqueduct's structure. A typical Roman aqueduct had a gradient of about 1:4800.

Underground tunnels

Aqueducts sometimes run for some or all of their path through tunnels constructed underground. A version of this common in North Africa and Central Asia that has vertical wells at regular intervals is called a qanat. One historic example found in Syria, the Qanat Firaun, extends over 100 kilometers.

Pipes

The Los Angeles Aqueduct

See also: Pipeline transport § Water

Modern aqueducts may also make extensive use of pipelines. Pipelines are useful for transporting water over long distances when it needs to move over hills, or where open channels are poor choices due to considerations of evaporation, freezing, pollution, or environmental impact. They can also be used to carry treated water.

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. It also help drought prone areas with water supplies. Some of the Roman aqueducts still supply water to Rome today. In California, United States, 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 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

• The Eupalinian aqueduct on the Greek island of Samos

Roman aqueducts

• The Pont du Gard, constructed in the 1st century, in Southern France.
• The Aqueduct of Segovia, an aqueduct bridge is one of the most significant and best-preserved ancient monuments left on the Iberian Peninsula, Segovia, Spain

Other aqueducts

• Ponte Mantible Aqueduct in Santiago se Compostela, Spain, 12th century.
• The Jerwan Aqueduct built by the Assyrian king Sennacherib dated to 688 BC, as part of the water supply system to the city of Nineveh
• Wignacourt Aqueduct, Malta; built in the 17th century to transport water from Dingli and Rabat to the new capital city Valletta; today, most of its arches still survive in the localities of Attard, Balzan, Birkirkara, Fleur-de-Lys and Santa Venera
• Aqueduct St-Clément, Montpellier, France, 17th century
• Bar Aqueduct, Montenegro, 16th century
• Águas Livres Aqueduct, in Lisbon, Portugal (built 1731–1748)
• Aqueduto de Óbidos, in Óbidos, Portugal (built 1570)
• Aqueduto de Setúbal in Setúbal, Portugal (built 1696)
• Aqueduto dos Pegões in Tomar, Portugal (built 1593)
• Água de Prata Aqueduct, in Évora, Portugal (built 1531–1537)
• Santa Clara Aqueduct, in Vila do Conde, Portugal
• Carioca Aqueduct in Rio de Janeiro, Brazil (built 1744–1750)
• Aqueduct of Teruel, Spain
• Aqueduc de Roquefavour, France, built between 1842 and 1847
• Greater Winnipeg Water District 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
• Surviving Spanish aqueducts in Mexico:
  • Aqueduct of Querétaro, Mexico, built between 1726 and 1738, 1.3 km long and featuring 74 arches
  • Aqueduct of Morelia, Michoacán, built between 1735 and 1738
  • Aqueduct of Acámbaro, Guanajuato, built in 1528
  • Chapultepec aqueduct, Mexico D.F.
• Kavala aqueduct, 16th-century Ottoman aqueduct in Kavala, Greece
• Levadas, 1,350 miles (2,170 km) of 17th century aqueducts on the Portuguese island of Madeira
• Espada Aqueduct, built 1735, in San Antonio, Texas, United States
• Quabbin Aqueduct, 24.6-mile (39.6 km) long tunnel, in Massachusetts, United States
• Chicopee Valley Aqueduct, 13.1-mile (21.1 km) long, in Massachusetts, United States
• Central Arizona Project Aqueduct
• California Aqueduct, a 715 mi (1,151 km) 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
• Croton Aqueduct, in New York State, United States, a large and complex water distribution system constructed for New York City between 1837 and 1842.
• Sooke Flowline located on Vancouver Island, Canada, is a 44 kilometres long, gravity-fed concrete pipe which provided water to the City Of Victoria for 55 years
• National Water Carrier of Israel located in Israel, is a 130 km long system of giant pipes, open canals, tunnels, reservoirs, and large scale pumping stations to transfer water from the Sea of Galilee in the north of the country to the highly populated center and arid south, built between 1953 and 1964

Gallery

• 

  View from inside a Roman aqueduct from the Pools of Solomon to Jerusalem

• 

  An entrance to the ancient Puquios, near Nazca

See also

• Earthquake engineering
• Goldfields Water Supply Scheme
• Leat
• List of aqueducts
• List of canal aqueducts in the United Kingdom
• List of Roman aqueduct bridges
• Pipeline – some used to carry water
• Roman architecture
• Roman engineering
• Sanitation in Ancient Rome
• Water resources

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 978-0-7844-0976-3)

External links

• Waterhistory.org: Imperial Rome Water Systems
• Romanaqueducts.info: 600 Roman aqueducts, with 25 descriptions in detail