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Aqueducts of Rome Under Augustus

Older Aqueducts (I)
Marcia, Tepula, Julia, Virgo and Alsietina Aqueducts (II)

by Al Schlaf

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The Augustan era was perhaps the greatest period of construction in ancient Rome. One of the more important aspects of this program was the repair and renewal of the city's system of aqueducts. At that time, the city was served by four aqueducts -- the Appia, Anio Vetus, Marcia and Tepula. All of these were in great need of repair and augmentation, since the most recent was almost a century old.[1] Up to Augustus' time, Rome had little time or resources for anything but minor work on the water supply. She had gone through the civil strifes of Marius and Sulla, a major slave revolt and two civil wars. Rome had grown to a population of close to one million and was in dire need of a better water supply. Augustus could see a distinct political advantage to the restoration and revamping of the water system. This would more firmly establish his regime and present a positive benefit to the populace.

In this article, the first of two parts, I will go into the establishment of the centralized water office and the restoration of the older aqueducts. In the second part, I will treat the construction of the new aqueducts-the Julia, Virgo and Alsietina. As an aid to the understanding of all these aqueducts, I refer you to the two illustrations below, showing the various aqueducts. They show all the aqueducts, including those post-date the reign of Augustus, one showing them on a map of modern Rome and one on ancient Rome.

Image 1: map of modern rome, thumbnail. Click here for larger picture. Image 2: map of ancient Rome, thumbnail. Click here for larger picture.
Click on images for enlargements

As with many difficult matters, Augustus chose M. Vipsanius Agrippa to carry out the new water program. At this time, Agrippa was both his son-in-law and his most able general. He had been praetor in 40, consul in 37 and was instrumental in the defeat of Sex. Pompeius in 36. Augustus set him to work repairing the Aqua Marcia in 34. In 33, Agrippa consented to go the reverse of the cursus honorum and take the lower rank office of aedile, in order to work full time on the project.[2] In this year, Agrippa extensively restored the Appia, Anio Vetus, Marcia, and combined the Tepula with a new aqueduct, the Julia. In order to accomplish such an extensive program, a central administration needed to be set up. According to Dio Cassius, he did this with his own funds[3] and staffed it with his own familia of slaves, at least for the maintenance of the system. According to Frontinus, this numbered 240 individuals, who were left to the state upon his death. The emperor Claudius added a later group of 460 from the familia publica to this at a later date. These numbers remained the same even up until the time of Frontinus, who was curator aquarum under Trajan[4] when he wrote his book on the subject. Agrippa is also credited with inventing the standard of measurement for the office, the quinaria. This, however, is not a measure of volume, but of capacity. It measured how much water could be discharged through a pipe 5/4 of a digit in diameter, flowing under constant pressure. This measures out to about 5,000 to 6,000 gallons per 24 hours. [5]

Agrippa continued unofficially as curator aquarum until his death in 12. In 11, Augustus named a new curator, M. Valerius Messalla Corvinus, who had previously served as praefectus urbis. He served until his death in 13 AD. He was succeeded by C. Atius Capito, who continued in office into the time of Tiberius. The Senate passed a series of consulta defining the powers and privileges of the office, also in 11.[6]

I will start with the restoration of the Appia. This was the oldest of the Roman aqueducts and by far the crudest.[7] Agrippa began his repairs on it in 33. Unfortunately, it cannot be determined to what extent, due to the lack of knowledge of its exact route outside of the city. However, one would expect it to have been extensive. Augustus in his later renovations from 11 to 4, augmented the Appia with a branch which joined it just outside Rome near the temple of Spes Vetus. This branch came to be known as the Ramus Augusta or just the Augusta Appia. This appears to have been in the vicinity of the Porta Maggiore.[8] There is a small section which might be it, just about a block inside of and a block to the left of the Porta Maggiore. It displays typical Augustan opus reticulatum lining and what appears to be either a thin covering of plaster or lime deposits from the water. I took some photos of it in 1973 and they can be seen below.

Image 3: Ramus Augusta Image 4: Ramus Augusta
Click on images for enlargements

It should be born in mind, though, that the Appia was the earliest aquaduct. At that time the Roman engineering was not at its peak. It and many of the earliest aqueducts were not borne aloft on the stately arches that we are accustomed to when we think of Roman aqueducts. They were constructed by a cut and cover method. This is where a trench would be dug, the channel lined with stone, or concrete, closed on top with corbeled or flat slabs and then covered over with earth. This had its advantages in that it was a simpler and less costly structure and also less likely to be attacked by enemies. Bear in mind that at the time of its construction, Italy and the environs of Rome were not unified. Rome still had enemies and a good source of water would be a tempting target. Buried, it was much less obvious. As can be seen in the second photo of this section, the aqueduct was still at ground level or just a little higher. The need for concealment was not needed, but the elevation was necessary for the continuation of the flow. Here it can be seen that the channel was now of arched concrete. The exterior shows some of the aggregate sticking out of the mass. Whether it was encased further for aesthetics, I do not know. Looking at the interior shots, you can see the fine opus reticulatum work mentioned above. Similar work can be seen in further photos on the Anio Vetus in this article.

Agrippa also restored the Anio Vetus in his aedileship and later by Augustus, who marked it with its only cippi. The intake of this aqueduct was discovered by Ashby in 1915, but has since been reburied. He found it to be of Augustan concrete. Further example of Augustan concrete has also been found on the section at Ponte degli Arci. At the Ponte Lupo, there remains a very deeply sunken shaft, which seems to be part of an inverted siphon. This shaft is supported by a thick buttress of large dimensions. The buttress and the shaft are both of Augustan concrete, faced both with tufa reticulate and small rectangular blocks. This all points to a reconstruction in the period of 11-4 by Augustus. The lack of any traces of a bridge or by-pass and the great depth of the shaft strongly point to the Anio Vetus passing beneath the stream in an inverted siphon and I illustrate this in the next two illustrations.

Image 6: Anio Vetus Image 5: Anio Vetus
Click on images for enlargements

The inverted siphon is a bold and costly device. It is used to carry the water across a valley or ravine, but without the massive substructures to bridge the valley at the same level as the surrounding valley sides. It works on the principle of water seeking its own level. As long as the "downstream" side is at or lower than the "upstream side", the water pressure and capillary attraction will maintain the flow. However, as Vitruvius notes,[9] there is need for standpipes to reduce the air pressure in the pipes and multiple pipes rather than just the one, also to reduce the pressure.

Image 7: Inverted Syphon
Click on image for enlargement
Roman architects usually avoided using this device due to the cause and potential pressure problems. They much preferred to detour around the obstacle in laying the channel. It is odd that they used it here, as the high lime content of the Anio would be expected to choke the small pipes used. Concrete pipes of a larger size would not be used, as the Romans did not regard concrete as suitable for this purpose.[10]

One other notable example of the Anio Vetus is to be found just outside the Porta Maggiore on the eastern side of the Via Labicana. Some of the sections in this area have been found showing both the original channel and the Augustan restorations. One of these sections, shown below, runs for 140 meters and is another fine example of Augustan opus reticulatum. The channel is constructed of gray, friable Augustan concrete. It is faced both on the channel proper and the substructures with a tufa reticulate. Similar work is to be found on the Anio Vetus inside the city in underground channels neat the intersection of the Via Principale Umberto and the Piazza Fanti as well as a reservoir. It also compares well with the work seen above on the Appia.

Since the next aqueduct, the Marcia, is often found in conjunction with the later Tepula and the Augustan Julia, I will treat that in the next part.

Thomas Ashby, The Aqueducts of Ancient Rome, OUP, 1935
S. Julius Frontinus, De Aquis Urbis Romae, Loeb Classical Library/Harvard University Press-Online: LacusCurtius • Frontinus on the Water Supply of Rome
C. Vitruvius Pollio, De Architectura-Online: Perseus Text, Lacus Curtius
Frederick W. Shipley, Agrippa's Building Activities in Rome, Washington University Studies, 1935
Time Life Books, Moses Hadas editor, Imperial Rome (Great Ages of Man Series), 1966
Esther Boise Van Deman, The Building of the Roman Aqueducts, Carnagie Institution of Washington, 1934

Photo Credits
1 and 2 - Frontinus (Loeb)
3 and 4 - author
5 and 7 - Van Deman
6 - Time Life

Footnotes 1. Dates for aqueducts were respectively 312, 272, 144 and 125. All dates here and in the rest of this article are BC.
2. Frontinus, De Aquis Urbis Romae, 9. Due to his prior offices and rank, probably as a curile aedile.
3. 49.43
4. 116
5. Frontinus, 25 and Clemens Herschel, Frontinus and the Water Supply of Rome.
6. Frontinus, 98-102, 104, 106, 108, 125 & 127; Tacitus, Annales, VI, 11.
7. The Aqueducts of Ancient Rome, pp.58-59.
8. The Building of the Roman Aqueducts, Esther Boise Van Deman, pp. 47-48
9. De Architectura, VIII, 6.5-6
10. Ashby, pp. 35-36

© Al Schlaf 2000

Al Schlaf earned a degree in Classical Languages and History at The Florida State University, with post graduate work at Florida State, University of Iowa and Trinity College of Hartford, Conn./Rome, Italy Campus.

He currently teaches in the Des Moines Public

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