During the Middle Ages, their complexity and grandeur gave rise to a legend amongst travelers. It was widely believed that such intricate and majestic structures could not be the work of mere mortals. Consequently, these spectacular aqueducts were often attributed to the mythical "giants."
Today, from the vantage point of a helicopter, we can still admire the remains of these Roman aqueducts that once dominated the landscapes of the mighty Roman Empire. Join us as we delve into the fascinating process of envisioning, designing, building, and maintaining a Roman aqueduct.
Finding the Perfect Water Source
The first critical step in creating an aqueduct was selecting an appropriate water source. The Romans would conduct extensive research, sampling, and testing to identify a suitable spring.
Once they discovered a potential spring, ideally located at a higher altitude than the intended city, they would scrutinize its quality.
The health of those who had previously consumed the water was studied meticulously. Despite limited scientific tools, the Romans would collect samples and taste the water over time, ensuring its safety and suitability for their aqueducts.
Determining the Correct Slope
The second stage in constructing an aqueduct involved calculating the slope. The Romans relied solely on gravity to pull water, necessitating a precise slope.
Therefore, the spring needed to be situated higher than its final destination. The calculation of the slope was foundational to the entire project. Ideally, the water pipeline should have an average slope of 2 per thousand.
With these methods, the Romans managed to take efficient and reasonably accurate initial measurements.
The dioptra, a Greek invention, was another vital tool. It enabled the Romans to determine the angle of the aqueduct both pre and post-construction, ensuring the slope remained consistent.
Purifying the Water
Once they had identified the source and calculated the slope, the Romans needed to ensure the water reached the city as pure as possible. They employed two effective methods for this purpose.
Firstly, they designed sedimentation tanks. Strategically placed along the aqueduct's route, these tanks allowed the water to stagnate temporarily. Consequently, leaves, slime, mud, and dust would settle at the bottom, purifying the water of harmful and polluting sediments.
The second method involved protecting the pipes from external elements. The aqueducts were covered with natural materials that did not release substances but prevented leaves, rain, and other external substances from contaminating the water.
Overcoming hills and valleys
The path of water faced two main obstacles: hills and, conversely, valleys.
In the first case, it was simply dug through the hills, respecting the environment and without blocking or creating harm to the surrounding land and inhabitants.
Depending on the morphology of the land, very deep valleys could also be encountered, and in that case there was a need to build supporting structures to fill the gap and maintain the calculated slope of the pipes.
It was for this reason that the Romans developed constructions based on arches: a structure that was easy to build, strong and capable of distributing weight very well.
Of course, the construction had to be solid. Sometimes it was not possible to build a single row of arches, because each arch would be too large, so they would create a row of larger arches and above that a second row of smaller arches to maintain some strength.
The inverted siphon technique
No matter how hard the builders tried to locate territories that were prepared for the construction of aqueducts, they occasionally came across valleys so deep and so inaccessible that it was impossible to think of obviating the problem by building a disproportionate number of arches.
In these borderline situations, the Romans exploited the principle of communicating vessels and used the technique of the inverted siphon (different from the modern siphon): water was made to collect in a huge, specially designed tank used for this purpose to accumulate weight.
The moment enough weight was accumulated, the water would fall by gravity and with a certain force down a pipe that rested on arches through the center of the valley.
With only a "run-up," the water was able to rise against the force of gravity from the opposite side and reach its destination, which was a pool located on the opposite side, slightly lower than the first.
The water, once it reached its destination, would end up in the distribution tank where any sediment would settle to the bottom for a final purification step, after which the system would distribute the fluid throughout the city.
In this way, most citizens had constant access to a continuous source of clean, controlled water, thanks in part to inspection wells that allowed them to check the condition of the facility at all times.
By the end of the third century, it is estimated that Rome had 11 functioning aqueducts. And the water flow rate of Rome's aqueducts was exceeded only by that of New York City in 1926.
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