Aqueduct (Roman)

The ancient Romans constructed numerous aqueducts to supply water to cities and industrial sites. These aqueducts were among the greatest engineering feats of the ancient world, and set a standard not equaled for over a thousand years after the fall of Rome. Many cities still maintain and use the ancient aqueducts for their water supply even today.

The Romans typically built aqueducts to serve any large city in their empire. The city of Rome itself, being the largest city, had the largest concentration of aqueducts, with water being supplied by eleven aqueducts constructed over a period of 500 years.

Engineering

The combined length of the aqueducts in the city of Rome was nearly 260 miles (416 km). (Hodge estimates the length at a little over 500 km). However, only 29 miles (47 km) were above ground, as most Roman aqueducts ran beneath the surface of the ground. Building underground helped to keep the water free from disease (the carcasses of animals would not be able to get into the aqueduct) and helped protect the aqueducts from enemy attack. The longest Roman aqueduct, the Zaghouan Aqueduct, is 57.5 miles (92.5 km) in length. It was built in the 2nd century to supply Carthage (in modern Tunisia).

The arcades, a series of arches, popularly shown to depict an aqueduct, should not be confused with the aqueduct itself. These arches sometimes on several tiers were constructed to carry the aqueducts over unavoidable dips, such as river valleys.

Roman aqueducts were extremely sophisticated constructions. They were built to remarkably fine tolerances, and of a technological standard that had a gradient of only 34 cm per km (3.4:10,000), descending only 17 m vertically in its entire length of 31 miles (50 km). Powered entirely by gravity, they transported very large amounts of water very efficiently (the Pont du Gard carried 20,000 cubic meters {nearly 6 million gallons} a day and the combined aqueducts of the city of Rome supplied around 1 million cubic meters (300 million gallons) a day (an accomplishment not equalled until the late 19th century and represents a value 25% larger than the present water supply of the city of Bangalore, with a population of 6 million). Sometimes, where depressions deeper than 50 m had to be crossed, gravity pressurized pipelines called inverted siphons were used to force water uphill (although they almost always used venter bridges as well). Modern hydraulic engineers use similar techniques to enable sewers and water pipes to cross depressions.

In addition to the expertise needed to build them, Roman aqueducts required a comprehensive system of regular maintenance to repair accidental breaches, to clear the lines of debris, and to remove buildup of chemicals such as calcium carbonate that naturally occur in the water.

Construction

Many tools were used in the construction of the aqueduct. An example of this is the chorobates. The chorobates was used to level terrain before construction. It was a wooden object supported by four legs with a flat board on top; in which was engraved a half circle. When used the half circle was filled with water and the angle at which there was no water was measured. Another tool used in the construction of the aqueduct was the groma. Gromas were used to measure right angles. A groma consisted of stones hanging off four sticks perpendicular to one another. Distant objects could be marked out against the station of the stones in a horizontal plane.

Decline of the aqueducts

With the fall of the Roman Empire, although some of the aqueducts were deliberately cut by enemies, many more fell into disuse from the lack of an organized maintenance system. The lack of functioning aqueducts to deliver water had a large practical impact in reducing the population of the city of Rome from its high of over 1 million in ancient times to considerably less in the medieval era.

List of Roman aqueducts

Aqueducts in the city of Rome

In order to meet the massive water needs of its huge population, the city of Rome itself was supplied with 11 aqueducts. Their combined capacity was capable of supplying at least 1,127,220 cubic meters (nearly 300 million gallons) of water to the city each day. Detailed statistics for the city's aqueducts were logged around 97 by Sextus Julius Frontinus, the curator aquarum (superintendent of the aqueducts) for Rome during the reign of Nerva. Less information is known about aqueducts built after Frontinus.

**Aqueducts in Rome**
Name	Year built	Length (km)	Height at source (m)	Height in Rome (m)	Capacity (m³ a day)
Aqua Appia	312 BC	16.561	30	20	73,000
Anio Vetus	272 - 269 BC	63.64	280	48	175,920
Aqua Marcia	144 - 140 BC	91.424	318	59	187,600
Aqua Tepula	125 BC	17.745	151	61	17,800
Aqua Julia	33 BC	21.677	350	64	48,240
Aqua Virgo	19 BC	20.697	24	20	100,160
Aqua Alsietina	2 BC ?	32.815	209	17	15,680 (not drinkable)
Aqua Claudia	38 - 52	68.681	320	67	184,280
Anio Novus	38 - 52	86.876	400	70	189,520
Aqua Traiana	109	32.500	-	-	-
Arcus Alexandriana	226	22	-	-	-

Other locations

The Romans built aqueducts in most sufficiently large cities in the Empire. Their remains (in some cases still functioning) may be found today in many places, including:

The Pont du Gard in southern France
Barbegal aqueduct, France
Eifel aqueduct, Germany
Caesarea Palaestina, Israel
Segovia, Spain
Mérida, Spain
Tarragona, Spain
Almuñécar, Spain (5 above ground aqueducts - 4 still in use)
Valens aqueduct, Istanbul, Turkey
Aspendos, Turkey
Aqua Augusta, Italy
Aqueduct of Hadrian, Tunisia

External links

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
Waters of the City of Rome -- provides sophisticated maps and images
Imperial Rome Water Systems
Roman Aqueducts Today
Lacus Curtius entry on Roman waterworks
600 roman aqueducts with 25 descriptions in detail
Map of Roman aqueducts

References

Coarelli, Filippo, Guida Archeologica di Roma, Arnoldo Mondadori Editore, Milano, 1989.
Claridge, Amanda, Rome: An Oxford Archaeological Guide, Oxford University Press, New York, 1998.
Hodge, A.T., Roman Aqueducts and Water Supply, Gerald Duckworth & Co, London, 2002.

Ancient Roman architecture

Aquädukte in Rom | Acquedotti di Roma | ローマ水道 | Lista de aquedutos de Roma

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