Roman aqueduct

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Pont du Gard, France, a Roman era aqueduct circa 19 BC. It is one of France's top tourist attractions at over 1.4 million visitors per year, and a World Heritage Site.

The ancient Romans constructed numerous aqueducts (Latin aquaeductūs, sing. aquaeductus) to supply water to cities and industrial sites. These aqueducts were amongst 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. ^[1]

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.

1 Engineering
2 Construction
3 Decline of the aqueducts
4 Lists of Roman aqueducts
5 See also
6 References
7 External links

[edit] Engineering

Image:Valens Aqueduct in Istanbul.jpg

Valens aqueduct in Istanbul

The combined length of the aqueducts in the city of Rome is estimated between 420 and a little over 500km. 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 was that of Constantinople (Mango 1995). "The known system is at least two and half times the length of the longest recorded Roman aqueducts at Carthage and Cologne, but perhaps more significantly it represents one of the most outstanding surveying achievements of any pre-industrial society". Perhaps the second longest, 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, together with tunnels, were constructed to maintain the pitch of the aqueduct, and the flow of water, over irregular terrain, for the long course to its destination.

Image:E5376-Tarragona-Aqueduct-channel.jpg

The water-carrying channel of the Tarragona Aqueduct

Roman aqueducts were extremely sophisticated constructions. They were built to remarkably fine tolerances, and of a technological standard that had a gradient (for example, at the Pont du Gard) of only 34 cm per km (3.4:10,000), descending only 17 m vertically in its entire length of 50 km (31 miles). Powered entirely by gravity, they could carry large amounts of water very efficiently. The Pont du Gard could transport up to 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. These figures were however functions of the catchment hydrology and aqueduct regulation technique as shown by recent studies. (For comparison the maximum value 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.

Image:Eifelwasserleitung05.jpg

A portion of the Eifel aqueduct, Germany, built in AD 80, showing the calcium carbonate that accretes on the sides of the channel without regular maintenance.

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.

[edit] Construction

Many tools were used in the construction of Roman aqueducts, one example being 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.

[edit] 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 decline 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, reaching as low as 30,000.

[edit] Lists of Roman aqueducts

[edit] See also

[edit] References

Bossy, G., Fabre, G., Glard, Y., and Joseph, C. (2000), Sur le Fonctionnement d'un Ouvrage de Grande Hydraulique Antique, l'Aqueduc de Nîmes et le Pont du Gard (Languedoc, France), Comptes Rendus de l'Académie des Sciences de Paris, Sciences de la Terre et des Planètes, Vol. 330, pp. 769-775.
Chanson, H. (2002), Certains Aspects de la Conception hydrauliques des Aqueducs Romains, Jl La Houille Blanche, No. 6/7, pp. 43-57.
Coarelli, Filippo, Guida Archeologica di Roma, Arnoldo Mondadori Editore, Milano, 1989.
Claridge, Amanda, Rome: An Oxford Archaeological Guide, Oxford University Press, New York, 1998.
Fabre, G., Fiches, J.L., and Paillet, J.L., L'Aqueduc de Nîmes et le Pont du Gard. Archéologie, Géosystème, Histoire, CNRS Editions, CRA Monographies Hors Série, Paris, France, 483 pages & 16 plates, 2000.
Gebara, C., Michel, J.M., and Guendon, J.L., L'Aqueduc Romain de Fréjus. Sa Description, son Histoire et son Environnement, Revue Achéologique de Narbonnaise, Supplément 33, Montpellier, France, 319 pages, 2002.
Hodge, A.T., Roman Aqueducts and Water Supply, Gerald Duckworth & Co, London, 2003.
Hodge, A.T., Roman Aqueducts & Water Supply, Duckworth, London, UK, 2nd edition, 504 pages, 2002.
Leveau, P. (1991), Research on Roman Aqueducts in the Past Ten Years, Future Currents in Aqueduct Studies, Leeds, UK, T. HODGE ed., pp. 149-162.
Mango, Cyril, The Water Supply' in Mango, C., and Dagron G., eds., Constantinople and Its Hinterland, Variorum, Aldershot, 1995.
O'Connor, C., Roman Bridges, Cambridge University Press, Cambridge, UK, 235 pages, 1993.