Arteries of an Empire

Valens Aqueduct, 2007. The same one that Justinian II used to spring his victory against the usurper Apsimar.

In the midst of a siege in 537, armies led by the Ostrogothic King, Vitiges, had trouble cutting the circulation of Rome. As the Greek writer Procopius tells it, Vitiges then devised a strategy to attack the city by clotting the aqueducts with his men, blocking the Roman water supply and bleeding the Roman citizenry dry. Nearly two centuries later, a similar urban shock would happen, in a far different place. In the year 705, the exiled emperor Justinian II dropped into Constantinople through the Valens Aqueduct. Like an embolism, he made his way into the eastern Roman capital, striking the head of Byzantium and successfully expelling his usurper.

As these two examples show, aqueducts were in many ways the lifeblood of a city in Late Antiquity. Water itself may not be interesting or impressive, but it was essential to urban living. From everyday needs such as quenching thirst, providing people a way of tending crops and washing clothes, to running mills and transporting goods, cities ran on fresh water. And in those cities which were unfortunate not to be located near convenient sources of it, Romans had long ago devised a way transport it over large swaths of land. The solution was the construction of aqueducts.

The oldest of the still extant aqueducts, the Aqua Appia, was the result of a major public works program, finished around 312 BCE. It remained the only aqueduct for around fifty years, before the Old Anio was built in 271 BCE. By the time of Julius Caesar, building aqueducts became another part of the public works programs that emperors saw as their duty. More aqueducts were built under Julius, Augustus, Claudius, and Trajan, with the last one being finished in 226 CE, close to a century before the beginning of “late antiquity.”

The Appia was also one of the aqueducts that Vitiges terrorized. It carried water from Tivoli, more than seventy kilometers north of Rome, and supplied the city with upwards of 73,000 cubic meters of water per day. Ancient engineers managed this by taking advantage of their naturally hilly terrain, setting up aqueducts to transfer water over a mostly-downward gradient over a large stretch of land. Most of the earliest Roman aqueducts actually ran underground; partly for the tactical reasons, but also to provide enough depth to transport the water. From a scientific or mathematical perspective, they may not have formulated Bernoulli’s Principle (that an increase in pressure and kinetic energy, in this case caused by gravity, increases the speed at which fluids move), but they understood it well enough to also utilize siphons whenever the aqueducts reached a steep valley.

An illustration of a siphon, courtesy of romanaqueducts.info

Since most of the aqueducts in the city of Rome had been built hundreds of years before  Late Antiquity, maintaining and restoring them continued to be one of the major duties of  late antique urban prefects, consuls and emperors. In fact, By the time of the high empire, control of the aqueducts had been left in the hands of an entire board of senators, along with their advisors and other officials. The notes left behind by Sextus Iulius Frontinus, one of these water commissioners, provides an in-depth look at the length, capacity, and methods of upkeep of the aqueducts.

For cities, the same care was lavished on them into Late Antiquity. Constantinople staked its claim as a great city built on the Roman model and featured a number of extraordinary aqueducts. Its most impressive aqueduct today was constructed under the Emperor Valens in 368. Stretching over 160 kilometers, through dense forests and over several valleys, the Valens Aqueduct serviced over 150 cisterns. Similarly well-preserved aqueducts can be found in the Pont du Gard in France (first century), the Caesarian aqueduct in Israel (thought to have been constructed by King Herod in the first century), and the Segovian aqueduct in Spain (possibly 112 CE). The size and architectural virtuosity puts these structures on par with any other late antique monumental buildings--and reminds us that not everything in a late antique city was always officially “late antique.”   

The Segovian Aqueduct in Spain, one of the oldest remaining structures from the Roman period.

Yet aqueducts served a purpose that was immediately more urgent to most late antique city dwellers. They supplied the waters for the baths, as well as in public spaces such as fora, particularly in the shape of fountains. Some aristocratic homes were even serviced directly by them—and control of water was a source of power. Both Vitiges and Justinian II understood that point well as both used the aqueducts to gain a tactical advantage. The Eastern Roman emperors would build land walls in order to fortify their water supply lines, or even open-air cisterns that necessarily laid outside of the city.

Still, water was not just purely functional, either. It could make a splash. While it was naturally important for urban life, the supervision, monumental building, and use of water in fountains was probably not an urgent necessary, especially given the decline in urban populations in western Europe following the 5th century. The Romans managed to secure so much water that they could waste it, and such waste was itself a claim to power over such a vital natural resource. The symbolism may not have lost on the multitudes of Late Antiquity. Much of Constantinople’s claim to be the “New Rome” came from its monumental architecture and urban development, both of which the Valens Aqueduct and the many public cisterns demonstrated.

Considering the difficulties of water management in the twenty-first century, the presence and functionality of aqueducts is particularly stunning. Water shortages and droughts throughout developing nations, and even in prominent ones such as the United States, continue to be an issue today. Aqueducts provided a solution to this issue that citizens in Late Antiquity took for granted. The methods by which engineers in Late Antiquity delivered water throughout the Empire demonstrates a marvelous ingenuity.