A group of scientists claims to have discovered a hydraulic system that was active for more than four centuries.

In Arles , a French city and former Roman province of Gaul, stone blocks covered in mineral deposits have been found , removed from the collapsed roof of a Roman baths.

This discovery has raised the possibility that it was a hydraulic system that had been active for more than 400 years. This operation had never been documented before, but it is known from the carbonate crusts that accumulated on the inner walls of the channels.

The Arles aqueduct is one of the most complex Roman infrastructures, and according to this study published in the journal Geoarchaeology, it is believed to have contained an innovative tool.

Researchers used carbonate deposits formed by the continuous flow of water as a geological archive and were able to reconstruct its evolution in detail. These deposits allow us to identify periods of clearing, changes in flow, or replacement of sections.

But the carbonate deposits are contaminated with clay and could not be dated using traditional methods like radiocarbon dating. So the team performed stable oxygen and carbon isotope analyses , which reflect annual variations linked to water temperature, source type, and even the residence time of the water in the channels.

"This allowed us to identify the same annual layers in the carbonates and thus determine their relative periods of deposition and, therefore, the historical chronology of the modifications made to the Arles water system," the scientists say.

In the remains of the roof of the hot chamber of the Baths of Constantine in Arles, researchers found reused fragments of the aqueduct's reservoirs. Analysis showed that these fragments came from sections that had been cleaned and reconditioned. This shows that the aqueduct was not only operational in the fourth century, but had also been restored to supply new public buildings.

The Arles hydraulic system was able to cross the Rhône River using an inverted lead siphon, a pipe that carried water beneath the channel, a fact that was not known about the direction in which the water flowed through these sub-river channels.

The carbonates inside the lead pipes were analyzed, and it was found that they carried water from Arles to the Trinquetaille district, on the other side of the river. Therefore, the inverted siphon carried the aqueduct's water beyond the Rhône, not just to Arles. This means that the hydraulic system was planned and adapted to the city's growth and water demand.