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Supplying Fresh Water to Roman Cities

The Romans' skill in civil engineering is one of the things that contributed greatly to the establishment of their civilization and empire. Their roads and bridges tied their empire together and made travel easier for Roman merchants, soldiers, and citizens (and pirates, for that matter). Their temples and great public buildings beautified their cities and many still stand as a testimony to their greatness. But it is the Romans' system of supplying water to their cities that, in this author's opinion, distinguishes the Romans as an advanced, modern civilization emerging from classical antiquity.

When human beings come to live together in communities any larger than small villages, the supply of water and the removal of waste become critical issues. The way these issues are dealt with determines whether the growing village becomes a thriving city or a backward and disease - ridden community. In small communities, individual households could manage the job of supplying themselves with fresh water from a stream or well. Likewise, it was the individual's responsibility to remove waste and garbage by burying it or carrying it beyond the walls of the village. As the village grew into a town, these jobs grew too large for the individuals to deal with efficiently and civic government had to take over. The Romans solved these problems by calling on their civil engineers to plan and build a centralized water distribution network and sewage system for every major town or city in the Republic. By the time of the late Republic and early Empire, Rome could boast one million inhabitants and several cities were home to several hundred thousand souls. The water supply to Roman cities had to reliably provide a continuous supply of fresh, clean water in order for these cities to survive. Likewise, an efficient sewer system had to be able to carry away wastewater from homes and buildings, as well as provide drainage for low areas of the city that might become swampy areas after a rainstorm.

Essentially, the way the Romans were able to supply water to their cities and cause the fountains in their cities to flow continuously was to use a system of aqueducts with a constant gradient and a system of cisterns and manifolds to hold and distribute the water. In non - engineering terms, a gradient is simply a slope expressed in numbers. The aqueducts and tunnels through hills that have survived have gradients ranging from one foot drop per 150 feet of length to one foot drop in about 500 feet of length. The Roman engineer Vitruvius recommended a gradient of not less than 1 in 200. By carefully choosing the gradient and maintaining it along the entire length of the aqueduct, the water could be made to flow fast enough to ensure a good supply yet not so fast that the aqueducts and pipes were washed out by the force of rushing water. The aqueducts usually went through tunnels when a hill lay in the way between a town and a water source. When the aqueducts crossed valleys or low places, they were built on top of arched causeways. Sometimes, when a very high aqueduct was needed, there were three courses of arches, one on top of the other, with the arches becoming smaller toward the top. A very beautiful example of this is the Pont du Gard near Nimes, in France, built while France was still the Roman province of Gaul. Some ancient cities just grew up on likely or easily defended spots, while some were very carefully planned out and engineered before a single street or building was built. In the latter case, the engineers would prospect for natural water sources and have a good idea of how much water they would supply before deciding on how large to make the town. Of course, the problem of urban sprawl and overpopulation often caused the city to outgrow its water supply if too many people moved in after the planning and engineering had been done, but the engineers would try to plan for this as well as they could. The type of water source they liked best was an artesian well or natural spring at the foot of a hill where the water flowed out all on its own. After carefully planning the gradient and building the aqueduct, they could expect a certain rate of flow of water from the source to the town. A well engineered system even took into account that there might be less water available from a spring during the Summer months. A good artesian well, however, would supply water at a constant rate all year long if one did not try to take more water out than it could supply.

After the water had flowed down the aqueduct into the town, it was usually directed into a manifold, or large distribution tank which feeds several large water mains that lead off into different areas of the city. This structure was constructed of masonry walls and was situated far enough above street level to cause water to flow at a reasonable rate by gravity into the city or town's water mains. These water mains were pipes made of sheet lead or terra cotta. The lead pipes were usually round or triangular in cross section and formed from a rectangular sheet of lead. The lead was rolled into a tube or folded into a triangle shape and the edges soldered together or folded over, crimped, and soldered together. The fountains were located on many street corners and water flowed into them by gravity. The excess water would flow down into another set of pipes to feed other fountains at lower levels throughout the hilly city of Rome. Finally, water would flow from the last in a chain of fountains into the cloaca, or city sewer system which would then discharge into a river as sewage. It was not the Romans' practice to turn the fountains off even though they knew how to build a valve to control the water. A story is told about Queen Christina of Sweden, a rather eccentric lady who had visited Rome and seen some of its fountains during the Seventeenth Century. After she had seen the fountains in St. Peter's Square, she told those giving her the tour that they could turn the fountains off, as she had already seen them. She was amazed to learn that the fountains of Rome had been running continuously day in and day out, year after year.

In the city of Rome, the aqueducts and the fountains they fed have been in use for centuries. Many of the ones in use today were built by the Romans between 312 BC and 200 AD. The first of Rome's eleven ancient aqueducts was built by the censor Appius Claudius Caecus in 312 BC. This is the same Appius Claudius Caecus who built the Via Appia, a road leading south out of Rome toward the territory of the Samnites, with whom the Romans were at war at that time. He is less well remembered in the popular mind as the builder of the Aqua Appia, the first aqueduct to carry water to the fast growing city of Rome. During ancient times, the city of Rome had between 1200 and 1300 public fountains, eleven large scale public baths, 867 smaller baths, and two artificial lakes used for mock naval battles. The city's eleven aqueducts delivered 38 million gallons of water to the city every day.

Managing such a large and complex municipal public works project as the water supply for the city of Rome required quite a lot of manpower. During the late First Century AD, Sextus Julius Frontinus, the curator aquarum or city official in charge of the water supply had seven hundred trained slaves in addition to several civil engineers who specialized in water and aqueducts working for him.

It is interesting to note that water was delivered to private homes via the city's water mains and metered with officially calibrated nozzles which were given an official stamp. Water usage into private homes was taxed, and two classes of service were available. Small houses were allowed a one half inch pipe connection to the water mains, while larger houses with baths were allowed a one and one half inch connection. When Frontinus first came into office, he audited the books and found that much more water was being used than could be accounted for in official records. He ordered his slaves to investigate, and found many illegal connections to the city's water system. He even found corruption in his own department, as many users had bribed his workers to allow them to tap into the water mains illegally so they could irrigate their gardens and crops. Frontinus prepared a very detailed record of the design and construction of Rome's water supply titled De Aquis Urbis Romae.

During the Fifth Century AD, most of the city's aqueducts were destroyed by the Ostrogothic warlord Vitiges when he placed Rome under siege during the war with the Byzantine emperor Justinian. Vitiges was not able to cut the city off entirely from its water supply, though, as he missed the Aqua Virgo. Most of this aqueduct runs underground.

During the Fifteenth Century, the popes began restoring Rome's aqueducts, most of which had fallen into disrepair after more than one thousand years. In 1429, while doing research at the library of Monte Cassino, a secretary to Pope Nicholas V happened upon De Aquis Urbis Romae, Frontinus' long forgotten manuscript describing the water works of Rome. Using this manuscript, workers were able to locate and repair the Aqua Virgo. From the Renaissance up until the time when Italy became a modern nation in the Nineteenth Century, the restoration of Rome's aqueducts was undertaken and financed by several of the popes. Plaques honoring some of these popes can be seen at some of the fountains in Rome today.

The subject of Roman civil engineering is a long and very interesting one, and the story of the municipal water system in Roman cities is especially so.. Some of the excellent books and articles used as reference material for this article include:

 

Macaulay, David   City: A Story of Roman Planning and Engineering   Boston: Houghton-Mifflin, 1974.

Landels, J. G.   Engineering in the Ancient World   Berkeley & Los Angeles: University of California Press, 1978.

James, Peter and Nick Thorpe   Ancient Inventions   New York: Ballantine, 1994.

Hamblin, Dora Jane   The Fountains of Rome   Smithsonian Magazine September, 1992.


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