On June 24, 109, Emperor Trajan opened the Aqua Traiana aqueduct, channelling fresh spring water from sources around Lake Bracciano to Rome, the bustling capital of his empire. The vast structure traversed the countryside to the Janiculum Hill, where it was used as bathing and drinking water for the locals, and also to power a series of water mills for industrial purposes like processing grain and sawing stone.
The springs around Lake Bracciano, about 25 miles northwest of Rome, were an important water source for the Ancient Etruscans. Around the year 100, Trajan started the construction of a nymphaeum at the site—a monument consecrated to the nymphs, young water goddesses—as well as the Aqua Traiana, which has survived up to the present day.
Trajan recorded many of his achievements in images on specially minted coins, The victory in Dacia was recorded on coins, as well as all the scenes on Trajan’s column, there was a coin for the new Forum Traiana in the centre of Rome, a new highway, the Via Traiana, and a new high quality, high capacity Aqueduct, the Aqua Traiana, which was to bring fresh spring water to all areas of the city.
In the beginning of Trajan’s reign, the curator of the city’s water supply was Sextus Julius Frontinus. He documented carefully the sources, routes and volumes of water supplied by the city’s existing aqueduct system, and this work, remarkably, has come down to us in modern times. In the time of Trajan the Roman city aqueduct system was quite old, and Frontinus’s work was focused on repairs and maintenance of an out of date system that no longer delivered enough water for a quickly increasing population.
Another problem was that all the existing aqueducts at that time came from the east of Rome, the sources were from rivers or springs providing water that carried dissolved salts and slime that were deposited inside and eventually blocked the pipes and ducts, and reduced the water flow.
Part of Trajan’s revised system was to bring in fresh spring water from the north-west of the city, water that was collected from fresh water springs distributed in the mountains around the Crater Lake known as the Lacus Sabatinus, today´s Lake Bracciano. The water was collected from many sources near the lake, filtered at source through volcanic ash aquifers and brought clockwise around the lake before heading down to Rome.
It is almost certain that it was taken over the river Tiber to supply Trajan’s new bath complex, and also to provide water for an artificial lake, a Naumachia, in the area that would become later known as the Vatican Hill.
The Aqua Traiana was damaged several times by the action of the Barbarians, but was restored and is believed to have kept running as late as the 9th or 10th century.
Camillo Borghese, on his accession in 1605 as Pope Paul V, initiated work on rebuilding the Aqua Traiana, supervised from 1609 by Giovanni Fontana. At that time, the Roman suburbs west of the Tiber River, including the Vatican, were suffering from chronic water shortage. The new pope persuaded the Municipality of Rome to pay for the development of an aqueduct to provide a better water supply to that part of the city.
In 1612, the aqueduct was completed. It was initially called the Acqua Sabbatina or Acqua Bracciano, but was renamed Acqua Paola in honour of Paul V.