In order to better understand the nomenclature used in this chapter it is recommended to give a quick look to the APPENDIX before reading the texts below. There the reader can find there some information on construction performances and management of ancient aqueducts.

Alsietinus and Trajan aqueducts

The courses of the Alsietinus and the Trajan aqueducts were practically parallel but are not completely known to us today. The exact starting points (Caput aquae) of both aqueducts as well the external sectors (normally built on archs) and terminals (castellum aquae) are known. In ancient times, both aqueducts would reach the same site, that is the district of Trastevere in Rome.  The underground course of Trajan aqueduct was marked with signaling stone artifacts called cippi. While the underground part of Alsietinus aqueduct is presumed, some confusion between the two aqueducts is evident, as it is shown in some plaques recalling restoration and renewing works performed within the centuries (refer to the APPENDIX:​ Aqua Alsietina and Aqua Traiana confusion). 

In the Trastevere area some watermills were installed: The significant jump accomplished by the water in coming down from the Janiculum Hill towards Trastevere suggested the hydraulic energy exploitation for wheels movement. The area has undergone several attacks by invaders of Rome due to the presence of the watermills and the system that supplied water to the Vatican Palaces.

Summary table of aqueducts at issue

Name of aqueductYear of
Daily water supply at source
Aqua Alsietina     2 BC16,26833
Aqua Traiana 109 AD118,20057
Aqua Paolina1612 AD80,00043
ACEA1997 AD95,000 max33

Alsietinus Aqueduct (Aqua Alsietina)

The aqueduct was constructed by Emperor Augustus in the year 2 BC, collecting water from Lake Martignano (Lacus Alsietinus) and terminating to Trastevere area. With the exception of around 500 m built overground on arcades its course was largely undergroundand that is why it not completely known today, however its total length is estimated to 33 km. Its initial section of 200 m length, is also known today and corresponds to the tunnel from which the water was taken from the lake. Recently, an urban section of the aqueduct has also been discovered near the existing Piazza San Cosimato, where was the basin for the naumachia (read more on Naumachia in the  APPENDIX).

The daily water supply capacity was only 392 quinary (equivalent to 16,268 m3/day): of these, 254 were reserved for the Emperor uses and the remaining 138 were granted to private use. The Emperor used the water primarily for the supply of the naumachia, and secondly for irrigation of the imperial gardens.

The life of the aqueduct was not very long, approximately in the 3rd century there was an important lowering of the Lake Alsietinus level (about 30 m) due to natural causes, leaving dry the mouth of the intake which is still visible today. From then on the aqueduct remained out of use.

Trajan’s Aqueduct (Aqua Traiana)

This aqueduct was built by Emperor Trajan in 109 AD, with a partial re-use of the previous Aqua Alsietina waterway. It used to gather waters from different springs of Sabatini Mountains, on NW of Lake Bracciano (Lacus Sabatinus) at an altitude of about 180 m a.s.l. The information on this aqueduct does not come from a single author, Frontinus was already dead, so they are fragmented between evidences of different authors. Due to this fact, the Trajan’s aqueduct has often been confused with the Alsietinus one (refer to the APPENDIX:​ Aqua Alsietina and Aqua Traiana confusion).

The first waterspring of uptake was probably the source of the Fiora stream that goes into the Lake Bracciano  (refer to the APPENDIX:​ Nymphaeum and Trajan Caput Aquae). These were the same springs used in the aqueduct built by the Orsini family in 1575 and then rebuilt by the Odescalchi family in 1727 (Odescalchi aqueduct), probably following the same course, to supply the little Ducky of Bracciano that had a few thousand of inhabitants. The aqueduct picked up the waters of the springs that fed the Bracciano basin.

The Trajan’s Aqueduct proceeded clockwise along the lake board till the resort “Marmotta” on SE shore and thenafter reached the city with a large underground route along the streets Clodia and Trionfale (several cippi are still visible along its path) and then prosecuted on wall over arches along the Via Aurelia Antica, before entering Rome.

The Trajan Aqueduct arrived in the area of Rome on the Janiculum Hill, on the right bank of the Tiber river at a level much higher than that of Trastevere areas (~ 75 m a.s.l.). To celebrate the successful completion of the aqueduct (June 109 AD), the Emperor Trajan made a special coin, a Sestertium. The distribution of that coin throughout the Empire had also the aim of notifying people that the aqueduct had been built at his own expenses (refer to the APPENDIX:​ Aqua Traiana celebration).

                    Image courtesy of Hydria Virtual Museum
Back side of the coins circulated in the Roman Empire when the Trahan Aqueduct was inaugurated. (Nanational Museum of Rome – Collection F.Gnecchi)

Hydria Virtual Museum

The Trajan’s Aqueduct was damaged and restored several times: 

  • it was cut off for the first time, together with other ancient aqueducts during the siege of Rome by Vitige King of the Ostrogoths, in 537 AD to stop the water supply to Rome; on the other hand Belisarius, the general counsel of Rome, closed the outlets to prevent access to the Ostrogoths. 
  • later it was restored by Belisarius and Pope Honorius I (7th century AD) and by the Popes Adriano I (8th century AD) and Gregory V (9th century AD), mainly to keep the watermills in use. 
  • it was damaged by the Longobards and the Saracens (8th and 9th century AD).
  • after the 9thcentury its maintenance was neglected due to a demographic collapse and shortages of technical and economic resources. The pipes were no longer usable and the Romans receded to drawing water from the River Tiber, wells and local springs. 
  • it was largely restored, as part of the Paulinus Aqueduct realization by Pope Paul V (17th century AD). 

The aqueduct of Trajan has been the penultimate of the eleven major aqueducts that have supplied Rome: Established in 109 AD, it remained nearly continously in use until the 9th-10th century AD, with some variation in water flow. In the 17th century AD some parts of it were reused for the Paulinus Aqueduct.

Paulinus Aqueduct (Aqua Paula)

The Trajan’s Aqueduct had developed some structural problems since the 15th  century AD:  its flow was very low and needed a massive restoration. Consequently, Pope Paul V, in the first decade of the 17th century AD, ordered its repair and the adaption of the existing aqueduct network, in the Sabatinus district, aiming to cover the water needs of Rome but also to enhance the beauty of the city with new monumental fountains. He was encouraged also by the fact that the level of Lake Martignano had again increased at his time.

The entire course including all its branches has a total lenthh of 43 km. It carries waters mainly from Lake Bracciano, through an inlet installed at Marmotta site, and partially from the forty residual springs of the pre-existing Trajan’s Aqueduct. Its flow capacity has been estimated to 80,000 m³ per day.

                    Image courtesy of Hydria Virtual Museum
Water catching point of Pauline aqueduct in Lake Bracciano (Marmotta site) (Photo G. Guerrieri).

Hydria Virtual Museum

The reconstruction work began in 1608, and the water reached the top of Januculum Hill only two years later, in 1610. This was possible to accomplish in such a short time because the entire course was divided into smaller sections, each of them assigned to different architects, who worked at the same time. The course of the previous water structures was partially modified and in 1614 the entire project was inaugurated feeding with water the districts of TrastevereVatican and Borgo.

Several fountains have been built at the terminals of the branches of the aqueduct, such as monumental fountain “Fontanone” on the Janiculum hills. Another fountain was erected in Trastever on Tiber side at Ponte Sisto, other two in Vatican, and some other smalls drinking fountains in Borgo.  With time, other non-drinking water was introduced to the duct, and consequently the Aqua Paola was used only to feed fountains and irrigate gardens, including the ones of the Vatican.

The contemporary ACEA Aqueduct

This is a joint Project of ACEA and Co.B.I.S. that supplies Rome with fresh water. ACEA is a utility company for water, energy and environment in charge, among other regions, for the area of Rome, while Co.B.I.S. is the consortium-manager devoted to municipal sewage treatment of the Sabatinuscatchment basin.

During the last century the water needs of Rome kept increasing, and in the 1980s a new duct from Lake Bracciano to the City was planned, that was actually put into operation in 1997. The water catching point of the ACEA Aqueduct is very close to that of the Paulinus one. The duct that collects water from the Lake, has been performed adjoining the Pauline Aqueduct course and has stopped in Trionfale district, where an appropriate sanitization plant can purify it if necessary.

                    Image courtesy of Hydria Virtual Museum
Scheme of the course of the cotemporary ACEA aqueduct (ACEA archives).

Hydria Virtual Museum

The water supply of the ACEA aqueduct is currently estimated to ~ 95,000 m3/d (based on an average value granted from the Ministry of Public Works). However, in order not to waste water resources, ACEA careful worked to collect the minimum amounts required that normally are greatly lower than those authorized.

In the early 1980s, the Association formed by the three neighboring Municipalities, the Province of Rome, the Region of Latium, ACEA and Co.B.I.S. constructed a main sewer around the lake that directs all the waste in a sewage treatment plant (see below).

The use of motor boats in the Bracciano Lake as well as the use of fertilizers and pesticides in the surrounding area were banned in 1987. This resulted to a broad recovery of the original purity of the habitat conditions in just a few years.

The ACEA and Co.B.I.S join project aimed primarily:

  • To ensure enough quantity of water for the Rome Municipality, especially as rescue, in summer time. The planned max delivery capacity is of about 30 million m3/y.
  • To ensure a high standard of the water quality of the Lake, since it is destined for human consumption. 
  • To improve the environmental quality of both the water Lake and the area comprised between Bracciano Lake and Roman sea resorts.

The improvement of the Bracciano Lake water quality, in terms of chemical and microbiological characteristics, was the main problem to be solved. The fact that the water is aimed for human consumption required many other actions in order to reach the targets.

At this purpose:

  • all uncontrolled sinks flowing towards the Lake have been cut off
  • organic agriculture practices have been adopted around the Lake
  • the circum-lacustrine sewer conveying urban liquid wastes to a treatment plant was built.

The sewer and the treatment plant

ACEA (Branch ATO 2 S.p.A) is charged of the management of the sewer around the lake, of conveying all the liquid waste in the treatment plant, and of operational/administration work in the treatment plant itself. The circum-lacustrine sewer runs around the Bracciano Lake with an extension of about 30 km and 24 pumping stations dedicated to orographic variations compensation.

                    Image courtesy of Hydria Virtual Museum
Image courtesy of Hydria Virtual Museum

Hydria Virtual Museum

The monitoring the urban liquid wastes pumping and management is assured by a technological advanced system equipped with Remote Terminal Units placed along the Lake board. Today the capacity of the Co.B.I.S. treatment plant is of about 90,000 inhabitant equivalents. Its daily average flux is of 0.25 m3/s. 

The treated waters are mainly discharged into the river Arrone (~ 21,600 m3/d). The sludge produced (~ 8.5 m3/d) is mainly reused in agriculture. 

These two aspects can be considered the other side of the coin because they still require an optimization in reuse and disposal. The current and diffuse water scarcity does not allow us to send treated water to the sea (through the river Arrone); a more significant utilization in agriculture or gardens has still to be developed also by lowering distribution costs. The reuse and valorization of sludge in agriculture has been rather developed.

In conclusion, the integrated  ACEA – Co.B.I.S. project has produced important results in line with the principles of sustainability (taking into account environmental, societal and economic parameters). They can be summerized in:

  • the improvement of Lake water quality in general
  • the increase in bathing activities (in free and organized beaches)
  • a greater diversity in biota
  • an improved fishery in terms of quality and quantity
  • the diffuse of organic agriculture practices in the area
  • the newly developed markets of local natural products
  • the better water quality of emissary river (Arrone) used also for irrigation
  • the amelioration of  the sea resort near Rome (Fregene) in terms of environment and health parameters thanks to a better water quality of Arrone at its estuary.