Aqueducts are channels, built above or under the ground, that carry water from a source to areas where the water is needed. The word aqueduct comes from two Latin words: aqua, meaning water, and ducere, meaning to lead. In the 500s B.C., the Greeks constructed simple aqueducts in Athens and on the island of Samos. It was the Romans, however, who became the greatest aqueduct builders in the ancient world. Their knowledge of engineering enabled them to improve their construction techniques and to erect elaborate aqueduct systems throughout their vast empire.

The first Roman aqueduct, the Aqua Appia, was built in 312 B.C.—the same year construction began on the first Roman road, the Via Appia, or Appian Way. (Both projects were named for the Roman official in charge of public works, Appius Claudius Caecus.) The Aqua Appia carried water to Rome from natural springs about ten miles outside the city. When this aqueduct could no longer provide enough water for the city, the Romans added a second one in 272 B.C. Known as the Aqua Anio Vetus, the new aqueduct brought water from the Apennines, a mountain range east of Rome. Over the next five centuries, nine additional aqueducts were constructed around Rome. Some parts of them are still in use. The Romans also built aqueducts throughout the empire in Greece, Italy, Spain, France, North Africa, and Asia Minor.

The major portion of most Roman aqueducts consisted of underground conduits, or tunnels. In the early systems, these conduits were made entirely of stone lined with mortar*. After the Romans learned how to make concrete from volcanic ash, they used concrete to build aqueducts. The Aqua Tepula, built in 125 B.C., was the first aqueduct constructed of poured concrete. The Romans also made pipes of clay, lead, and bronze to carry water through the concrete conduits.

The Roman system of aqueducts relied on gravity, allowing water to flow from higher elevations to lower ones. Roman engineers took advantage of natural slopes in the terrain. If aqueducts had to cross ravines, or narrow valleys between hills, the Romans erected great stone bridges to carry the water across. These bridges, with their distinctive arches, were the most striking features of ancient Roman aqueducts. Two of these beautiful bridge aqueducts survive today in Segovia, Spain, and in Nimes, France.

* mortar mixture of lime, cement, sand, and water that is placed between stones to hold them together

When the water from an aqueduct reached a city, it went first to a system of brick-and-concrete tanks called castella, or castles. From there, the water was channeled to public baths and fountains and to private customers. Some of the water was used to flush out the city sewers. A city official called an aedile had responsibility for overseeing the water system, including the aqueducts. In times of drought, water supplies to private homes were cut off. Public fountains, on the other hand, were always supplied with water.

Aqueducts were expensive to build and maintain. For this reason, Romans generally built them to supply water to large cities. Smaller cities and towns throughout the Roman empire had to rely on local wells and springs or on simple underground pipelines for their water supply. As the Roman Empire began to decline in the late A.D. 300s and 400s, its system of aqueducts began to deteriorate as well. In the centuries that followed, Roman aqueducts were neglected and most fell into ruin. (See also Construction Materials and Techniques; Waterworks.)

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