Tracking down ancient maintenance work: Examination of an aqueduct in south-west France has provided insights into Roman water management and local social development. The researchers were able to show how the regular decalcification of the pipe system secured the water supply of the Gallo-Roman city of Divona Cadurcorum. The archaeological findings match a written tradition about maintenance work on aqueducts in the Roman Empire. In the late phase of the use of the Divona aqueduct, however, the social decline at the end of antiquity becomes apparent, the scientists report.
They are one of the hallmarks of Roman civilization: aqueducts supplied many cities of the empire with water, sometimes over great distances. Even today you can admire the remains of these technical masterpieces in some places. An international team of researchers with participation from the Johannes Gutenberg University in Mainz has been researching ancient water management for some time. In the current study, the scientists have now dealt with one of the oldest known aqueduct systems in France: it dates from the early first century AD. and supplied the city of Divona Cadurcorum, today's Cahors.
The pipe system brought water from a spring in the Vers Valley to the city's fountains and baths, some 32 kilometers away. Long stretches of the aqueduct's channel were carved into the rock and further built as a brick conduit. The construction was probably up to the 4th or even 5th century AD. in use. "The aqueduct is an impressive feat of engineering," says lead author Gül Sürmelihindi from the University of Oxford. As the researchers explain, Roman water management was often confronted with a problem that many people are still familiar with from washing machines today: calcification. Because aqueducts, which were located in limestone regions, as in the case of Divona, carried “hard”, mineral-rich water. Even then, the dissolved calcium carbonate fell out during transport in the canal and was deposited on the walls and floor. Wherever they threatened to clog the water pipes, the limescale deposits were removed by maintenance work.
Maintenance patterns are emerging
The scientists have now examined these deposits and the traces of processing from the late phase of the use of the Divona aqueduct using modern analysis techniques. As they explain, temperature-dependent features of the deposits reflected what time of year they formed. This resulted in a profile similar to that of tree growth rings. The researchers were able to obtain indications of maintenance work from clear chipping marks, but also from fine deformations on the calcite crystals that can be traced back to the impact of tools. By combining the findings, the team was then able to obtain more precise information about the maintenance work.
It became apparent that the intervals between the individual maintenance work were one to five years and an average of 2.8 years. The temporally high-resolution data also enabled more detailed conclusions: “Each cleaning was carried out quickly and probably lasted a month at most. It also never took place in the summer, when people needed the most water,” says Sürmelihindi. As the team points out, this pattern fits a surviving text by the Roman senator Sextus Iulius Frontinus, in which he makes "recommendations" for the maintenance of the city of Rome's aqueducts. It is therefore now archaeological evidence of the only known treatise that dealt with the subject.
Socioeconomic Notes
Another discovery during the investigation were the traces of two repairs in the canal system. A reddish, waterproof mortar was applied - the so-called Opus Signinum. As can be seen, in contrast to the cleaning work, the flow of water was interrupted for a longer period of time for these measures. "It's strange to see such long pauses and to imagine how the locals managed without a continuous water supply," says Sürmelihindi.
The results of the investigation also reflect that in the last phase of the use of the Divona aqueduct, the cleaning work was carried out less and less until finally the water supply system was abandoned. "This is probably due to a decline in population or to the fact that fewer resources were available for maintenance," says co-author Cees Passchier from the University of Mainz.
According to the team, this shows once again that the study of aqueducts can provide important information on societal and socio-economic developments. Sürmelihindi says: "Regular maintenance can be taken as evidence of the well-structured organization of an ancient city, while less regular maintenance or its complete absence could indicate socio-economic stress," says the geoarchaeologist. The researchers hope that their concept can now increasingly establish itself as a helpful tool in archaeological research.
Source: Johannes Gutenberg University Mainz, specialist article: Scientific Reports, doi: 10.1038/s41598-023-38655-z