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.
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.
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.
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.
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.
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 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 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 term aqueduct is often applied specifically to a bridge for carrying water.
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.
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.
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 kilometres (54 mi) 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.
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.
In China, the South–North Water Transfer Project aims to connect the Yangtze River basin to Beijing through three separate systems. The project will reuse part of the Grand Canal of China.
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.
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.
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.
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.The Eupalinian aqueduct on the Greek island of Samos
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
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
St-Clément Aqueduct, Montpellier, France, 17th century
Bar Aqueduct, Montenegro, 16th century
Águas Livres Aqueduct, in Lisbon, Portugal (built 1731–1748)
Óbidos Aqueduct, in Óbidos, Portugal (built 1570)
Setúbal Aqueduct in Setúbal, Portugal (built 1696)
Pegões Aqueduct 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)
Teruel Aqueduct, Spain
Roquefavour Aqueduct, 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
Kamares, Larnaca, Cyprus