Anaqueduct is awatercourse constructed to carry water from a source to a distribution point far away. In modern engineering, the termaqueduct is used for any system of pipes, ditches, canals, tunnels, and other structures used for this purpose.[1] The termaqueduct also often refers specifically toa bridge carrying an artificial watercourse.[1]
Aqueducts were used inancient Greece, theancient Near East,ancient Rome,ancient Aztec, andancient Inca. 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.
Although particularly associated with the Romans, aqueducts were devised much earlier in Greece, theNear East,Nile Valley, andIndian subcontinent, where people such as theEgyptians andHarappans built sophisticated irrigation systems. The Aztecs and Incans also built such systems independently later. Roman-style aqueducts were used as early as the 7th century BC, when theAssyrians 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.[2]
Although particularly associated with theRomans, aqueducts were likely first used by theMinoans around 2000 BC. The Minoans had developed what was then an extremely advancedirrigation system, including several aqueducts.[3]
The Indian subcontinent is believed to have some of the earliest aqueducts. Evidence can be found at the sites of present-dayHampi, Karnataka. The massive aqueducts nearTungabhadra River supplying irrigation water were once 15 miles (24 km) long.[4] The waterways supplied water to royal bath tubs.
InOman from theIron Age, in Salut, Bat, and other sites, a system of underground aqueducts calledfalaj 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.
Scheme of aqanat, an underground form of aqueduct popular in ancient Persia
InPersia, starting around 3000 years ago[5] a system of underground aqueducts calledqanāts 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 the need for pumping. The water drains relied 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.
ThroughoutPetra, Jordan, theNabataean 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 theSiq, 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.
On the island ofSamos, theTunnel of Eupalinos was built during the reign ofPolycrates (538–522 BC). It is considered an underground aqueduct and brought fresh water toPythagoreion for roughly a thousand years.
The multiple arches of thePont du Gard, inRoman Gaul. Its lower tiers carry a road across the river, and the upper tiers support an aqueduct conduit that carried water toNimes.
Roman aqueducts were built in all parts of theRoman Empire, from Germany to Africa, and especially in the city of Rome, where they totalled over 415 kilometres (258 mi). 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 termaqueduct is often applied specifically to abridge for carrying water.[1]
Near the Peruvian town of Nazca, an ancient pre-Columbian system of aqueducts calledpuquios 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.[6]
TheGuayabo 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.[7] The aqueducts are constructed from rounded river stones, which are mostly made ofvolcanic rock.[8] 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.
Extensive usage of elaborate aqueducts have been found to have been used in ancientSri Lanka. The best example is theYoda Ela or Jaya Ganga, an 87 kilometres (54 mi) long water canal carrying excess water between two artificial reservoirs with agradient 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.[9]
Modern aqueducts are a central part of many countries' water distribution infrastructure.The United States' aqueducts are some of the world's largest. TheCatskill 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 242-mile (389-km)Colorado River Aqueduct, which supplies the Los Angeles area with water from the Colorado River nearly 250 miles to the east and the 701.5-mile (1,129.0 km)California Aqueduct, which runs from theSacramento-San Joaquin River Delta toLake Perris. TheCentral Arizona Project is the largest and most expensive aqueduct constructed in the United States. It stretches 336 miles from its source nearParker, Arizona to the metropolitan areas ofPhoenix andTucson.
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 ofOamaru.
In Spain, theTagus-Segura Water Transfer system of aqueducts opened in 1979 and transports water 286 kilometres (178 mi) from north to south.[10]
The simplest aqueducts are smallditches cut into the earth. Much larger channels may be used in modern aqueducts, for instance theCentral Arizona Project uses 7.3 m (24 ft) wide channels.[11] 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.[12]
Artificial rills, known locally asBächle, flank several streets in the old quarter ofFreiburg, Germany.An artificial rill, part of theFalaj water transportation system, atAl AinOasis, in theAbu Dhabi Emirate.
A constructed functionalrill is a small canal or aqueduct of stone, brick, concrete, or other lining material, usuallyrectilinear incross section, forwater transportation from a source such as a river, spring, reservoir,qanat, or aqueduct for domestic consumption or agricultural irrigation of crop land uses.
Rills were traditionally used inMiddle Eastern andMediterranean climate cultures of ancient and historical eras; and other climates and continents worldwide. They are distinguished from a 'waterditch' by being lined to reduce absorption losses and to increase durability. TheFalaj irrigation system at theAl AinOasis, in present-dayAbu Dhabi Emirate, uses rills as part of itsqanat water system. Sometimes in theSpanish language they are calledAcequias.
Rills are also used for aesthetic purposes in landscape design. Rills are used as narrow channels of water inset into the pavement of agarden, as linearwater features, and often tiled and part of a fountain design.
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.[13]
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 ofevaporation, freezing, pollution, or environmental impact. They can also be used to carrytreated water.
Historically, agricultural societies have constructed aqueducts to irrigate crops.Archimedes invented thewater screw to raise water for use in irrigation of croplands.
Another use for aqueducts is to supply large cities with drinking water. They also help drought-prone areas withwater supply. Some of the Roman aqueducts still supply water to Rome today. InCalifornia, United States, three large aqueducts supply water over hundreds of miles to the Los Angeles area. Two are from theOwens River area, and a third is from the Colorado River.
In moderncivil engineering projects, detailed study and analysis ofopen-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.
^Remini, B.; Kechard, R.; Achour, B. (2014-12-01). "THE COLLECTING OF GROUNDWATER BY THE QANATS: A MILLENNIUM TECHNIQUE DECAYING". Larhyss Journal (20): 259–277.
^Alvarado, Guillermo E.; Soto, Gerardo J. (1 October 2008). "Volcanoes in the pre-Columbian life, legend, and archaeology of Costa Rica (Central America)".Journal of Volcanology and Geothermal Research.176 (3):356–362.Bibcode:2008JVGR..176..356A.doi:10.1016/j.jvolgeores.2008.01.032.
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