Roman Aqueduct Information

The Romans constructed numerous aqueducts to bring clean water from distant sources into cities and towns, supplying private households, public baths and public fountains. The waste water was flushed into the public sewers. Some aqueducts served water for mining and processing, manufacturing, and mills.

Aqueducts brought water from source to destination through gravity alone. Most were stone-covered, lined leats, laid more or less along the ground contours but with an added, slight downward gradient to ensure adequate flow. Where valleys must be crossed directly, the conduit was supported on costly, masonry-piered bridgework; some aqueducts employed an impressive but less reliable technology of high pressure ceramic or lead syphons for the same purpose. The building of an aqueduct required an accurate ground survey and careful engineering, and regular inspection and maintenance thereafter to clear any accumulated deposits and debris, and to minimise loss of water through leakage and theft. Aqueducts built to supply potable water could include sedimentation tanks, sluice gates, and storage cisterns to augment the supply en route, or at the water's destination. Masonry arches, siphons and cisterns were very costly. Of all aqueduct designs, the simple, sometimes temporary open leats used for industrial supplies were the cheapest to build.

With reliable aqueduct technology available, the expansion of Roman towns and cities was no longer limited by their dependence on local water resources. Rome's first aqueduct was built in 312 BC, during the Republican era, presumably because the expanding city had outstripped its local water supply; a further eleven aqueducts were built there over the next 500 years, supplying enough water to meet the needs of approximately 1,000,000 persons at the height of the city's development in the Imperial era. The well-preserved remains of similar projects can still be found in former cities of the Roman Empire; examples include the Aqueduct of Segovia and the aqueduct-fed cisterns of Constantinople. The funding of new aqueducts and the maintenance of the system as a whole was an enormous expense, essential to the public interest and public health. Costs were met by the State, cities, municipalities and private benefactors.

Methods of aqueduct surveying and construction are given by Vitruvius in his work De Architectura (1st century BC). The general Frontinus gives more detail, in his official report on the problems, uses and abuses of Imperial Rome's public water supply.

Background

Prior to their acquisition and development of aqueduct technology, Romans founded their settlements conveniently close to clean, reliable water-sources, such as springs and streams. These supplies were augmented by groundwater from privately or publicly owned wells, and by rain-water drained from rooftops into storage jars and cisterns.^[1] While individual households, small settlements and villas relied on such resources throughout the Roman era, the growth of larger municipal and urban communities was limited by the local availability of fresh water. The provision of public water, bath complexes and fountains in towns and cities were increasingly seen as fundamental signs of a civilised, Roman life.^[2]

Engineering

"The extraordinary greatness of the Roman Empire manifests itself above all in three things: the aqueducts, the paved roads, and the construction of the drains."

The volume of water actually transported depended on the catchment hydrology – rainfall, absorption, and runoff – and the quality of maintenance. Springs were by far the most common sources, as in most of the aqueducts that supplied the city of Rome, but some systems used water from reservoirs such as the two, still in use, that once supplied the aqueduct at the provincial city of Emerita Augusta.^[4]

The combined length of the aqueducts in the city of Rome is estimated between 490 to a little over 500 miles, of which approximately 29 miles (47 km) were carried on masonry supports. Most Roman aqueducts ran beneath the surface of the ground. The longest Roman aqueduct system 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).

Arches are often used to depict an aqueduct but 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, from its source to its destination.

Roman aqueducts were built to remarkably fine tolerances; for example, the gradient of the Pont du Gard is only 34 cm per km (3.4:10,000), descending only 17 m vertically in its entire length of 50 km (31 mi). It could transport up to 20,000 cubic meters — nearly 6 million gallons — a day.

The combined aqueducts of the city of Rome supplied around 1 million cubic meters (300 million gallons) a day: a capacity 126% of the current water supply of the city of Bangalore, which has a population of 6 million.

Sometimes, where depressions deeper than 50m 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); four inverted siphons crossed river valleys in the Aqueduct of the Gier, one of the four aqueducts that supplied Lugdunum (Lyon). Modern hydraulic engineers use similar techniques to enable sewers and water pipes to cross depressions. Where sharp gradients were unavoidable, the conduit could be stepped, or its width increased by a receiving tank, to disperse the flow and reduce its abrasive force.^[5] Once constructed, Roman aqueducts required a comprehensive system of regular maintenance to repair accidental breaches, to clear the conduits of gravel and other loose debris, and to remove the hard accretions of water-borne chemicals such as calcium carbonate. Lead pipe inscriptions provided information on the owner to prevent water theft.

The methods of building aqueducts and the surveying needed to ensure a regular water supply is described by Vitruvius in Book 8 of his De Architectura. The work specifies the tests needed to ensure that the water is potable, and he warns against lead pipes for their toxicity, recommending either masonry channels or clay pipes. He suggests a low gradient of not less than 1 in 4800 for the channel, presumably to prevent damage to the structure. This value agrees well with the measured gradients of surviving masonry aqueducts, but many temporary aqueducts, such as those used for hydraulic mining at Dolaucothi in Wales and Las Medulas in northern Spain, are much higher. At Dolaucothi, the gradient of the main 7 mile long structure is about 1:700, considerably higher than those of the permanent masonry aqueducts. Vitruvius also describes the construction of inverted siphons and the problems of blow-outs where the pressures were greatest.

At Barbegal, in Roman Gaul, a single aqueduct drove a cascaded series of 15 overshot water mills that ground flour for the Arles region.

Construction of Roman aqueducts

The aqueducts required very careful planning before building, especially to determine the water source to be used, the length of aqueduct needed and its size. Great skill and training were needed to ensure a regular grade so that the water would flow smoothly from its source without the flow damaging the walls of the channel. As the need for water grew, extra sources would be utilized, very often making use of existing structures as with the Aqua Claudia and Anio Novus in Rome. The problems of aqueduct building and use are described by Vitruvius and Frontinus, the latter producing a long report on the state of the aqueducts of Rome in the last years of the 1st century AD.

Several surveying tools were used to facilitate construction. Horizontal levels were checked using a chorobates, a flatbedded wooden frame fitted with a water level. Courses and angles could be plotted and checked using a groma; this relatively simple apparatus was probably displaced by the more sophisticated dioptra, precursor of the modern theodolite.

Industrial aqueducts

Many aqueducts were built to supply water to industrial sites, such as gold mines, where the water was used to prospect for ore by hydraulic mining, and then crush and wash the ore to extract the gold. They usually consisted of an open channel dug into the ground, with a clay lining to prevent excessive loss of water and sometimes with wooden shuttering. They are often known as leats. However, they were built just as carefully as the masonry structures, but often at a higher gradient so as to deliver the greater volumes needed for mining operations.

The large quantities of water supplied by the aqueducts were used for prospecting for ore-bodies by stripping away the overburden, and for working the ores in a method known as hushing. The technique was used in combination with fire-setting, which involved creating fires against the hard rock face to weaken the rock and so make removal much easier. These methods of mining survived into Medieval times until the widespread use of explosives. The water could also be used to wash ores, especially those of gold and tin, and probably to work simple machines such as ore-crushing hammers and water wheels.

The remains of such leats are visible today at sites like Dolaucothi in south-west Wales, and at Las Medulas in northwest Spain. These sites show multiple aqueducts, perhaps because they were relatively short-lived and deteriorated rapidly. There are, for example, at least seven major leats at Las Medulas, and at least five at Dolaucothi feeding water from local rivers direct to the mine head. At Dolaucothi, they used holding reservoirs as well as hushing tanks, and sluice gates to control flow, as well as drop chutes for diversion of supplies. The palimpsest of such channels allows the mining sequence to be inferred.

Some aqueducts were used for mills, such as the dramatic site of Barbegal, where one aqueduct fed sixteen mills arranged in two columns down the side of the hill. There was a similar arrangement on the Janiculum at the terminus of Aqua Traiana, the highest aqueduct of the many feeding Rome.

There are a number of other sites that were fed by several aqueducts but have not yet been thoroughly explored or excavated, such as those at Longovicium near Lanchester south of Hadrian's wall. It appears that the water supplies may have been used to power stamp mills for forging iron.

Decline in use

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. During the Renascence, the standing remains of the city's massive masonry aqueducts inspired architects, engineers and their patrons; Pope Nicholas V renovated the main channels of the Roman Aqua Virgo in 1453.^[6] Previously Pedro Tafur, a Spanish visitor in 1436, unconsciously revealed that the very nature of the Roman aqueducts was popularly misunderstood:

Through the middle of the city runs a river, which the Romans brought there with great labour and set in their midst, and this is the Tiber. They made a new bed for the river, so it is said, of lead, and channels at one and the other end of the city for its entrances and exits, both for watering horses and for other services convenient to the people, and anyone entering it at any other spot would be drowned.^[7]

On the other hand, many aqueducts elsewhere in the empire were kept in good repair. The aqueduct at Segovia in Spain shows advances on the Pont du Gard by using fewer arches of greater height, and so greater economy in its use of the raw materials. The skill in building aqueducts was not lost, especially of the smaller, more modest channels used to supply water wheels. Most such mills in Britain were developed in the medieval period for bread production, and used similar methods as that developed by the Romans with leats tapping local rivers and streams.

See also

• Aqueduct
• List of aqueducts in the Roman Empire
• De aquaeductu
• De Architectura
• Dolaucothi
• Frontinus
• Hydraulic mining
• Hydrology
• Leat
• List of Roman aqueduct bridges
• Roman architecture
• Roman engineering
• Sanitation in Ancient Rome
• Vitruvius

Notes

1. ^ Mays, L., (Editor), Ancient Water Technologies, Springer, 2010, pp. 115 - 116.
2. ^ Gargarin, M. and Fantham, E., (editors), The Oxford Encyclopedia of Ancient Greece and Rome, Volume 1, Oxford University Press, 2010, pp. 144 - 145.
3. ^ Quilici, Lorenzo (2008): "Land Transport, Part 1: Roads and Bridges", in: Oleson, John Peter (ed.): The Oxford Handbook of Engineering and Technology in the Classical World, Oxford University Press, New York, ISBN 978-0-19-518731-1, pp. 551–579 (552)
4. ^ Mays, L., (Editor), Ancient Water Technologies, Springer, 2010. p. 116.
5. ^ Mays, L., (Editor), Ancient Water Technologies, Springer, 2010. p. 119.
6. ^ Gross, Hanns (1990). Rome in the Age of Enlightenment: the Post-Tridentine syndrome and the ancien regime. New York: Cambridge University Press. p. 28. ISBN 0521372119.
7. ^ Pedro Tafur, Andanças e viajes.

References

• Blackman, Deane R., Hodge, A. Trevor (2001) "Frontinus' Legacy", University of Michigan Press.
• Bossy, G.; G. Fabre, Y. Glard, C. Joseph (2000). "Sur le Fonctionnement d'un Ouvrage de Grande Hydraulique Antique, l'Aqueduc de Nîmes et le Pont du Gard (Languedoc, France)" in 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 hydraulique des Aqueducs Romains", Journal La Houille Blanche, No. 6/7, pp. 43–57.
• Chanson, H. (2008). "The Hydraulics of Roman Aqueducts: What do we know? Why should we learn ?" in Proceedings of World Environmental and Water Resources Congress 2008 Ahupua'a, ASCE-EWRI Education, Research and History Symposium, Hawaii, USA, Invited Keynote lecture, 13–16 May, R.W. Badcock Jr and R. Walton Eds., 16 pages (ISBN 978-0-7844-0976-3)
• Coarelli, Filippo (1989). Guida Archeologica di Roma. Milano: Arnoldo Mondadori Editore.
• Claridge, Amanda (1998). Rome: An Oxford Archaeological Guide. New York: Oxford University Press.
• Fabre, G.; J. L. Fiches, J. L. Paillet (2000). L'Aqueduc de Nîmes et le Pont du Gard. Archéologie, Géosystème, Histoire, CRA Monographies Hors Série. Paris: CNRS Editions.
• Gebara, C.; J. M. Michel, J. L. Guendon (2002). "L'Aqueduc Romain de Fréjus. Sa Description, son Histoire et son Environnement", Revue Achéologique de Narbonnaise, Supplément 33. Montpellier, France.
• Hodge, A.T. (2001). Roman Aqueducts & Water Supply, 2nd ed. London: Duckworth.
• Leveau, P. (1991). "Research on Roman Aqueducts in the Past Ten Years" in T. Hodge (ed.): Future Currents in Aqueduct Studies. Leeds, UK, pp. 149–162.
• Lewis, P. R.; G. D. B. Jones (1970). "Roman gold-mining in north-west Spain", Journal of Roman Studies 60 : 169-85.
• Lewis, P. R.; G. D. B. Jones (1969). "The Dolaucothi gold mines, I: the surface evidence", The Antiquaries Journal, 49, no. 2: 244–72.
• Tucci, Pier Luigi (2006). "Ideology and technology in Rome’s water supply: castella, the toponym AQVEDVCTIVM, and supply to the Palatine and Caelian hill", Journal of Roman Archaeology 19 : 94-120.

External links

• Sextus Julius Frontinus, De Aquaeductu Urbis Romae (On the water management of the city of Rome), translated by R. H. Rodgers. University of Vermont, 2003.
• Imperial Rome Water Systems, waterhistory.org
• Roman Aqueducts Today, dl.ket.org
• Lacus Curtius – entry on Roman waterworks, uchicago.edu
• 600 Roman aqueducts – with 25 descriptions in detail, romanaqueducts.info
• (Italian) Map of Roman aqueducts, archeoroma.com
• Roman Aqueduct Manual – NOVA outline, pbs.org
• [1] – Recent advances in study of Roman aqueducts by Chanson
• Hubert Chanson – A dozen freely available published research articles on Roman aqueduct hydraulics and culvert design, and related topics by Professor Hubert Chanson, Department of Civil Engineering, University of Queensland.
• ItalianAware- Provides a convenient outline of Roman aqueducts, along with pictures and dates, italianaware.com
• John Hooper, Secrets of Roman aqueduct lie in chapel, guardian.co.uk, 24 January 2010 – likely source of Trajan's Aqua Traiana found at Lake Bracciano

Categories:

• Roman Inventions
• Ancient Roman architecture
• Roman aqueducts
• Water

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