roman aqueducts

Roman aqueducts and their construction

In this article you will find a lot of information about the Roman aqueducts, how they were built, how the source of origin was chosen, how the route was chosen, etc, etc. These are notes taken from the two chapters on aqueducts of the Roman Engineering series and other sources that I leave at the end.

When many people talk about aqueducts, they think of arches, like those of the Segovia aqueduct, but that is only part of it. The aqueduct is all the channeling from the spring or source of origin to the destination city, and on this journey the water is conducted through different channels, from buried lead pipes, tongue-and-groove rock pipes, channels, rock tunnels, from inverted siphons, decanters, distributors to the arches, everything is part of a great work of hydraulic engineering.

Key elements

The Romans were always looking for sources of great quality and flow. They never supplied water from rivers or swamps to the cities, but from the best springs, bringing water from wherever it was needed.

Water is the fundamental factor for Roman cities. It was very important to have a continuous and quality supply. Throughout the article you see examples of the enormous efforts they made to bring running water to different cities. And it is something that is repeated throughout the entire empire.

They did not use lifting mechanisms such as Archimedean screws although they were familiar with them. they used gravity, the elevation of the city is always lower than that of the fountain. So did the cities and canals. Determining the level of the spring and the level at which the city was or should be.

They could not make the channels with little slope because it would sediment when the water went too slowly and it would clog them. On the other hand, if it was too steep, there was too much current that eroded the channeling. They work with slopes that oscillate between 10 cm and 50 cm per km.

To find out the path along which the aqueduct should run, the topography is divided with a horizontal plane that starts from the area of ​​the fountains and reaches the area of ​​the city and in this way the different possibilities for where to take it can be seen.

The Romans used different tools. The dioptra to measure geodesic points to triangulate (Geodesy)

All the channels were closed and in most of the land they were buried. They have a waterproofing layer made from lime and ground ceramic (Opus ninum)

They made tunnels and arches to shorten the path. They used water level to control slopes.

Calcareous concretion, lime that is being fixed to the walls.

castelum divisorium. Place where the water came and divided. The surplus water went to the sewers to keep them always clean.

Castellum aquae. It is a deposit located in the upper part of the city where the water from the aqueduct came.

Examples of Aqueducts

examples of roman aqueducts

How many are there in Spain?

Nemausus 860k inhabitants) is nimes

Tiermes aqueduct

Modest city located in Soria and despite that they make a 6km aqueduct in terrain with a lot of rock.

As we have said, the entire empire was full of modest cities with impressive aqueducts that required a lot of effort to build.

Cella Aqueduct

Aqueduct from Albarracín to Cella, 25 km long. A watershed transfer occurs. Take water from the Turia basin instead of the Ebro.

It has a 5 km long tunnel with its manholes, a great work and economic effort for another modest town. There are manholes 70 meters high, with a lower diameter of 1 meter but as it rises, they have dug in the shape of a truncated cone, ending up with colossal wells.

They were looking for joints to make it easier to drill.

Chelva Aqueduct

They don't know where it supplied, they think it could be Lliria. Could it be Sagunto, which is 40 km away. Find springs and sources near Sagunto.

Bilbilis Aqueduct

It is very high. It is known for its large number of cisterns. It is ruled out that they store rainwater after the efforts seen in other cities. The rainfall is low and with cisterns at high points. They would never fill with rain. In addition to the importance that the Romans gave to running water, a topic that we have already discussed.

Sagunto is a much more important city (see oblation in Roman times and theater and circus capacity)

They have an upper entrance and an upper exit, but not a lower one, so they are decanters. They cannot be emptied by gravity. If you want to store you have to have a lower outlet

Italica Aqueduct

35 km aqueduct. It has a group of cisterns. The decanters are normally placed at the end of the aqueduct near the cities.

In Bíbilis there are 20 cisterns/decanters. There is a significant height gradient between the highest and lowest points and they set up a network so that the pipe does not burst.

They are equidistant in height, about 10m apart so that it does not exceed 1 atm.

To raise the water to Bilbilis they use an inverted U-shaped siphon that uses the principle of communicating vessels.

(See the different types of Roman concrete)

See the Use of siphons and inverted siphons, which the Romans used very well.

Pergamum had between 7 and 8 aqueducts from different eras. It was common to have more than 1 aqueduct to guarantee the water supply.

Madradar aqueduct, Source more than 30 km away, the flow from various sources was gathered, in pipes for 12 km

40 km of buried pipes saving a drop of 860m

30 cm lead pipe in drilled stone ashlars. A 3,5 km lead siphon with a pressure height of 190 m

Lugdunum Aqueduct, Lyon

It has 4 large aqueducts. The most important is the Hier aqueduct with 85 km of channel, the source is 40 km in a straight line.

Lead and metals were looted and this explains why there is not a trace left. Metals were very precious. In Sagunto we have the via del portico where you can see lead pipes.

Tarraco aqueduct

The route of its aqueduct is unknown. Sometimes arches were used to show off, because the works were paid for by public figures, but it could have been solved with inverted siphons or other techniques already known to the Romans.

Aqueduct of Segovia

Segovia aqueduct, one of the best known in the world

The same thing happens with this aqueduct. The arches are unnecessary. The city was humble and little water circulated through the cashier, which is small.

Almost everything is unknown about this 28 m high and 127 m long aqueduct with 167 arches and 24 granite blocks

There is a poster that announces the sponsor of the work.

Uxama Aqueduct

46 km of aqueduct with a 12 m elevation difference. There are cisterns at a higher level than the arrival point. A decanter 40m above the finish line.

They think that the water was raised with a well known as rosario

Arles aqueduct

It has 2 aqueducts from 20 to 30 km. They converged 10 km from Arles in a distribution arch.

Other aqueducts

Aqueducts and Roman Engineering
  • Cherchel
  • Aix en Provence
  • Brevenne (70 km)
  • Frejús
  • Gades (100 km)
  • Cologne (100km)
  • Aspendos
  • Cartago (130 km with 16 km of arches)
  • Valente
  • Constantinople (400 km) one of the largest hydraulic works of the ancient world
  • Las Médulas, gold mining, several aqueducts were built that together exceeded 600 km in length
  • Rome, 11 aqueducts, some 100 km long, supplying 1000 billion m3 a day to the city

Sources and references

can be seen in RTVE and completed with information from talks and videos of the Isaac Moreno Gallo's Youtube channel and other readings.

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