An aqueduct is a conduit or system of conduits engineered to convey water. Modern aqueducts use pipes, ditches, canals, tunnels, and support structures to transport water from a source to a distribution point, supplying cities and agricultural lands, especially those with limited water access. Aqueducts also improved public health by delivering drinking water free of contamination in cities with poor sanitation systems. The Romans were great aqueduct builders, but systems existed in Persia, India, and Egypt centuries earlier. Roman aqueducts, built throughout their empire, stretched long distances, using gravity to move water and excess to flush sewers.

Why were aqueducts important in ancient times?

Aqueducts were crucial in ancient times because they supplied areas with limited direct access to fresh water, which was especially important for the development of cities and agricultural lands. They also improved public health by keeping drinking water free of human waste and contamination, which was particularly important in cities that had primitive sewerage systems. The Romans were known for building aqueducts throughout their empire, and their arches can still be seen today in Greece, Italy, France, Spain, North Africa, and Asia Minor.

How does an aqueduct carry water from one place to another?

Aqueducts transport water from a source to a distribution point using gravity and a system of canals, pipes, and tunnels. The water flows through the aqueduct due to a slight downward slope, maintaining a constant flow. Ancient Roman aqueducts primarily used underground conduits made of stone or terra-cotta pipes, with only portions elevated on stone arches to cross valleys. Modern aqueducts utilize materials like reinforced concrete and ductile iron for large water mains and smaller underground pipes, respectively. These systems can span hundreds of miles, supplying water to urban areas and agricultural projects.

What materials were used to build ancient aqueducts?

Ancient aqueducts were marvels of engineering, essential for conveying water to cities and agricultural lands. The Romans, renowned for their aqueducts, constructed them using a variety of materials, including cut stone, brick, rubble, and a type of rough concrete. Most of Rome's aqueduct system comprised underground conduits made of stone and terra-cotta pipe, but wood, leather, lead, and bronze were also used. Channels were constructed of cut stone, brick, rubble, or rough concrete. Pipes were typically made of drilled stone or of hollowed wooden logs, although clay and lead pipes were also used. When crossing valleys, arcades of massive granite piers and arches supported the aqueducts. The introduction of pulvis puteoli , or pozzolana, a volcanic material, created weather-resistant mortar that would harden even underwater.

How did engineers solve the problem of crossing valleys or rivers with aqueducts?

To cross valleys or rivers with aqueducts, Roman engineers used arcades consisting of one or more levels of massive granite piers and arches to support the aqueducts when crossing a valley. Roman bridges and aqueducts are known for using the circular arch form, which allowed for longer spans than stone beams and more permanent bridges than wood. Where multiple arches were needed for longer bridges, building strong piers was critical. When piers couldn't be built on rock, the Romans developed the cofferdam, a temporary enclosure made from wooden piles driven into the riverbed, sealed with clay, and filled with concrete. The Pont du Gard aqueduct near Nîmes in southern France, has three tiers of semicircular arches, with the top tier rising more than 45 meters (150 feet) above the river.

How are modern aqueducts different from those built in ancient times?

While modern aqueducts share the same fundamental purpose as their ancient counterparts—to convey water—they differ significantly in engineering and materials. Ancient aqueducts, like those of Rome, relied on gravity and were constructed primarily from stone, brick, and concrete. Modern aqueducts, however, utilize advanced materials such as steel, ductile iron, and reinforced concrete, allowing for greater durability and pressure resistance. Modern systems also incorporate pumping stations, enabling them to traverse varied terrains, unlike the gradient-dependent ancient systems. The scale of modern aqueducts far surpasses that of ancient ones, with some stretching hundreds of miles to supply urban areas and irrigation projects. For example, the California Aqueduct extends approximately 700 km (440 miles).

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The Pont du Gard, a three-tiered ancient Roman aqueduct with large stone arches, spans a river near Nimes, France, surrounded by trees and rocky banks.

How did ancient Jerusalem resist Babylon's siege for so long?

Aerial view of the Los Angeles Aqueduct winding through dry, hilly terrain with mountains in the background.

At a Glance

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Key People:: William Mulholland; Appius Claudius Caecus; Thomas Telford; Montgomery C. Meigs

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Top Questions

What is an aqueduct?
An aqueduct is a conduit or system of conduits engineered to convey water. Modern aqueducts use pipes, ditches, canals, tunnels, and support structures to transport water from a source to a distribution point, supplying cities and agricultural lands, especially those with limited water access. Aqueducts also improved public health by delivering drinking water free of contamination in cities with poor sanitation systems.

The Romans were great aqueduct builders, but systems existed in Persia, India, and Egypt centuries earlier. Roman aqueducts, built throughout their empire, stretched long distances, using gravity to move water and excess to flush sewers.
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Why were aqueducts important in ancient times?
Aqueducts were crucial in ancient times because they supplied areas with limited direct access to fresh water, which was especially important for the development of cities and agricultural lands. They also improved public health by keeping drinking water free of human waste and contamination, which was particularly important in cities that had primitive sewerage systems. The Romans were known for building aqueducts throughout their empire, and their arches can still be seen today in Greece, Italy, France, Spain, North Africa, and Asia Minor.
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How does an aqueduct carry water from one place to another?
Aqueducts transport water from a source to a distribution point using gravity and a system of canals, pipes, and tunnels. The water flows through the aqueduct due to a slight downward slope, maintaining a constant flow.

Ancient Roman aqueducts primarily used underground conduits made of stone or terra-cotta pipes, with only portions elevated on stone arches to cross valleys. Modern aqueducts utilize materials like reinforced concrete and ductile iron for large water mains and smaller underground pipes, respectively. These systems can span hundreds of miles, supplying water to urban areas and agricultural projects.
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What materials were used to build ancient aqueducts?
Ancient aqueducts were marvels of engineering, essential for conveying water to cities and agricultural lands. The Romans, renowned for their aqueducts, constructed them using a variety of materials, including cut stone, brick, rubble, and a type of rough concrete.

Most of Rome's aqueduct system comprised underground conduits made of stone and terra-cotta pipe, but wood, leather, lead, and bronze were also used. Channels were constructed of cut stone, brick, rubble, or rough concrete. Pipes were typically made of drilled stone or of hollowed wooden logs, although clay and lead pipes were also used. When crossing valleys, arcades of massive granite piers and arches supported the aqueducts. The introduction of pulvis puteoli, or pozzolana, a volcanic material, created weather-resistant mortar that would harden even underwater.
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How did engineers solve the problem of crossing valleys or rivers with aqueducts?
To cross valleys or rivers with aqueducts, Roman engineers used arcades consisting of one or more levels of massive granite piers and arches to support the aqueducts when crossing a valley. Roman bridges and aqueducts are known for using the circular arch form, which allowed for longer spans than stone beams and more permanent bridges than wood.

Where multiple arches were needed for longer bridges, building strong piers was critical. When piers couldn't be built on rock, the Romans developed the cofferdam, a temporary enclosure made from wooden piles driven into the riverbed, sealed with clay, and filled with concrete. The Pont du Gard aqueduct near Nîmes in southern France, has three tiers of semicircular arches, with the top tier rising more than 45 meters (150 feet) above the river.
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How are modern aqueducts different from those built in ancient times?
While modern aqueducts share the same fundamental purpose as their ancient counterparts—to convey water—they differ significantly in engineering and materials.

Ancient aqueducts, like those of Rome, relied on gravity and were constructed primarily from stone, brick, and concrete. Modern aqueducts, however, utilize advanced materials such as steel, ductile iron, and reinforced concrete, allowing for greater durability and pressure resistance. Modern systems also incorporate pumping stations, enabling them to traverse varied terrains, unlike the gradient-dependent ancient systems.

The scale of modern aqueducts far surpasses that of ancient ones, with some stretching hundreds of miles to supply urban areas and irrigation projects. For example, the California Aqueduct extends approximately 700 km (440 miles).
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1. aqueduct
2. water supply system: Developments in supply systems
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aqueduct, (from Latin aqua + ducere, “to lead water”), conduit built to convey water. In a restricted sense, aqueducts are structures used to conduct a water stream across a hollow or valley. In modern engineering, however, aqueduct refers to a system of pipes, ditches, canals, tunnels, and supporting structures used to convey water from its source to its main distribution point. Such systems generally are used to supply cities and agricultural lands with water. Aqueducts have been important particularly for the development of areas with limited direct access to fresh water sources. Historically, aqueducts helped keep drinking water free of human waste and other contamination and thus greatly improved public health in cities with primitive sewerage systems.

Although the Romans are considered the greatest aqueduct builders of the ancient world, qanāt systems were in use in ancient Persia, India, Egypt, and other Middle Eastern countries hundreds of years earlier. Those systems utilized tunnels tapped into hillsides that brought water for irrigation to the plains below. Somewhat closer in appearance to the classic Roman structure was a limestone aqueduct built by the Assyrians about 691 bce to bring fresh water to the city of Nineveh. Approximately two million large blocks were used to make a water channel 10 metres (30 feet) high and 275 metres (900 feet) long across a valley.

The elaborate system that served the capital of the Roman Empire remains a major engineering achievement. Over a period of 500 years—from 312 bce to 226 ce—11 aqueducts were built to bring water to Rome from as far away as 92 km (57 miles). Some of those aqueducts are still in use. Only a portion of Rome’s aqueduct system actually crossed over valleys on stone arches (50 km out of a total of about 420 km); the rest consisted of underground conduits made mostly of stone and terra-cotta pipe but also of wood, leather, lead, and bronze. Water flowed to the city by the force of gravity alone and usually went through a series of distribution tanks within the city. Rome’s famous fountains and baths were supplied in that way. Generally, water was not stored, and the excess was used to flush out sewers to aid the city’s sanitation.

James Watt as a young man, c1769. Scottish engineer and instrument maker. Invented the modern steam engine which became the main source of power in Britain's textile mills. His engine had a separate condenser in which steam from the cylinder; (see notes)

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Roman aqueducts were built throughout the empire, and their arches may still be seen in Greece, Italy, France, Spain, North Africa, and Asia Minor. As central authority fell apart in the 4th and 5th centuries, the systems also deteriorated. For most of the Middle Ages, aqueducts were not used in western Europe, and people returned to getting their water from wells and local rivers. Modest systems sprang up around monasteries. By the 14th century, Brugge, with a large population for the time (40,000), had developed a system utilizing one large collecting cistern from which water was pumped, using a wheel with buckets on a chain, through underground conduits to public sites.

Major advances in public water systems since the Renaissance have involved the refinement of pumps and of pipe materials. By the late 16th century, London had a system that used five waterwheel pumps fastened under the London Bridge to supply the city, and Paris had a similar device at Pont Neuf that was capable of delivering 450 litres (120 gallons) per minute. Both cities were compelled to bring water from greater distances in the next century. A private company built an aqueduct to London from the River Chadwell, some 60 km (38 miles) distant, that utilized more than 200 small bridges built of timber. A French counterpart combined pumps and aqueducts to bring water from Marly over a ridge and into an aqueduct some 160 metres (525 feet) above the Seine.

One of the major innovations during the 18th and 19th centuries was the introduction of steam pumps and the improvement of pressurized systems. One benefit of pumping water under pressure was that a system could be built that followed the contours of the land; the earlier free-flowing systems had to maintain certain gradients over varied terrain. Pressurization created the need for better pipe material. Wood pipes banded with metal and protected with asphalt coating were patented in the United States in 1855. Before long, however, wood was replaced first by cast iron and then by steel. For large water mains (primary feeders), reinforced concrete became the preferred construction material early in the 20th century. Ductile iron, a stronger and more elastic type of cast iron, is one of the most common materials now used for smaller underground pipes (secondary feeders), which supply water to local communities.

Modern aqueducts, although lacking the arched grandeur of those built by the Romans, greatly surpass the earlier ones in length and in the amount of water they can carry. Aqueduct systems hundreds of miles long have been built to supply growing urban areas and crop-irrigation projects. The water supply of New York City comes from three main aqueduct systems that can deliver about 6.8 billion litres (1.8 billion gallons) of water a day from sources up to 190 km (120 miles) away. The aqueduct system in the state of California is by far the longest in the world. The California Aqueduct conveys water about 700 km (440 miles) from the northern (wetter) part of the state into the southern (drier) part, yielding more than 2.5 billion litres (650 million gallons) of water a day.

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