All thriving civilizations demonstrate excellent water engineering, illustrated by religions, ancient myths, and philosophers as well as modern day technologies. In fact, some of the first Greek and Roman philosophers wrote about the importance of water to a society – including Alcmaeon of Croton, who connected water quality to health, and Vitruvius, who wrote about how to assess the quality of water sources . Civilizations from the once thriving ancient Petra in the desert to modern day refugee camps finding alternate sources of water to serve a huge population influx exemplify this need for excellent water engineering for the success of a civilization. Rome is an example of a thriving civilization with proficient water engineering, not only for practical use but also as a display of status. From the ancient city boasting large public baths to the grand fountains of the 16th century, Rome has no shortage of water displays. These water features are indicators of prosperity; this article will explore how Rome’s proficiency in water engineering over its history demonstrates signs of status, going a step beyond the practical uses of water. Specifically, this paper reviews the fountains of Rome and how these water displays in turn represent symbols of wealth or status.
2. Trevi Fountain
The Trevi Fountain, pictured in Figure 1, was completed in 1762 and marks the end of the Aqua Virgo. It features many mythological figures and is carved into the side of a palace about 26 meters tall . The fountain took over one century to complete and is recognized as an important example of Baroque architecture .
3.1 Water Supply: Aqua Virgo
The Trevi Fountain is supplied by the Aqua Virgo, an aqueduct originally completed in 19 BC. The aqueduct was mostly constructed underground, with short stretches utilizing arcades to cross valleys . Figure 2 shows the makeup of an ancient Roman aqueduct, illustrating how arcades were used to transport water across valleys. The aqueducts serve to transport freshwater from surface water or storage through conduits on top of arcades and siphons. Gravity alone was utilized to transport enough water for most of the civilization, yet the aqueducts had very small gradients to do so. In fact, the aqueducts had a theoretical minimum slope of 0.3% . The surveying, design, and construction labor behind creating aqueducts that transported such high amounts of water over large distances and varying terrains demonstrates a civilization with the wealth to do so.
These arcades were built partly from travertine, a limestone that was quarried in Ancient Rome . It is still quarried and used as a building material around the world today – as pictured in Figure 3 on a tour of the Pacifici Cava, a modern travertine quarry – though not as building blocks because it is too expensive.
Aqua Virgo derives its water from a marshy area and begins east of Rome, as shown in Figure 4. It stretches to about 14 miles total. Though the aqueduct is considered resilient due to it mostly being underground, it has also been repaired many times, beginning under Emperor Claudius when arcades were constructed across major roads through Rome. The aqueduct was later shortened as a result of issues with a sharp turn during its route through Rome, which resulted in high energy losses and cavitation due to loss of pressure. Ultimately, the Romans created the aqueduct’s end where Trevi Fountain is now. Under Sixtus IV, heavy maintenance became required; the conduit was cleaned, and the arcades were repaired with travertine recycled from a unknown destroyed arch. The practice of reusing materials from previous structures was common for the Romans, as exemplified by Aqua Virgo. Finally, in the 15th century, the fountain began to dry out, prompting more changes to the aqueduct, though these were poorly documented. The more recent repair between 1550-1565 was put in place to address issues with the conduit that was leaving the aqueduct nearly dry. One major aspect of these repairs was reinforcing the arcades with bricks, which some engineers argued would make the arches weaker because plants could grow between the bricks and the original structure. However, this aqueduct is still used to supply water to the Trevi Fountain along with several other fountains throughout Rome today. Most of these repairs were a result of collaboration between the Emperor and the Pope, with the Pope providing the major funding for these works .
The design, construction, and labor put into the Aqua Virgo demonstrates a great wealth of the leaders of Rome which allowed for the Trevi water display. The impressive water engineering and surveying in addition to the large amounts of labor over many eras of Rome illustrate this further.
3.2 The Trevi Fountain Water Display
The Trevi Fountain attracts many tourists, day and night, for its impressive display of water. While the Trevi Fountain has acted as a water delivery system to the people, with its water often being praised for its quality and taken in barrels to the Vatican, the fountain facade itself designed with the enjoyment of the popes in mind. Figures 5 and 6 demonstrate this elaborate design. When it was initially being constructed in 1629, modifications were made to the square so that it was visible from the Palazzo del Quirinale by the popes from an order by Pope Urban VIII, requiring the demolition of houses in order to increase the size of the fountain. This ultimately paused construction after the Pope’s death and after a struggle for enough material to complete the fountain, the fountain was recommissioned in 1732 and completed in 1762 . From the elaborate facade to the large waterfalls, the fountain represents another water display used as a sign of status in Rome, particularly as it was engineered to be seen by the popes.
Not only did the Trevi Fountain require incredible water engineering, surveying, and construction for the transport of water, it also was designed with the wealthy and high status people in mind. This affected the incredible design of the facade as well as the related construction activities. The Trevi Fountain represents an example of the wealth and status that enable Rome’s fountains.
3. Villa d’Este
Villa d’Este is located in Tivoli, Italy and includes the mansion and gardens of Cardinal Ippolito II d’Este of Ferrara, who first ordered the villa to be built in 1550. The gardens, filled with many monumental fountains, were meant to illustrate his wealth and status; d’Este’s villa would later be recognized as a prime example of the Italian Renaissance water garden . The gardens have over fifty fountains in total, ranging in size and style. While a few of these fountains use pumps today, they were originally designed only using gravity to feature such impressive water displays . Pictured in Figures 7-9 are some examples of the fountains featured at Villa d’Este.
3.1 Cost of Construction
The feat of engineering required to build the Villa d’Este gardens represents a display of wealth by d’Este, who commissioned the gardens as a representation of his status. The cost of the gardens has many factors, including the hydraulic engineering, breadth of construction, and materials used in the villa. d’Este required expert hydraulic engineers who designed the fountains based on gravity as well as included artists who created mosaic details throughout the gardens, pictured in Figure 10. Further, the construction of the gardens required large-scale excavations and demolitions. This includes the creation of the canals for water supply, the installation of underground pipes throughout the gardens, and the excavation of the site itself. The cost of labor for these activities was high, particularly without modern machinery to make these processes easier. In addition, the garden features marble at many points, further highlighting how the fountains at Villa d’Este mark a sign of wealth and prosperity .
The intricacies in the design of the gardens also played a role in the high cost of construction. The fountain included “398 spouts, 364 jets, 64 waterfalls, 220 basins (of various shapes and sizes, and 875 linear meters of water chains and canals” as well as underground systems which can be described as a “hydraulic machine” powered only by gravity, as discussed in Section 3.2 . Each of these components required materials, design, and construction labor to put in place, illustrating the high cost of the gardens. Figure 11 shows the complex system of canals, tunnels, and pipes which required extensive design and attention to detail, signifying the number of design hours behind these fountains. While the exact cost of construction is difficult to quantify, the size of the gardens, the material and labor required for construction, and the hydraulic engineering expertise required for the gardens to come to life signals the wealth and status behind the Villa d’Este.
3.2 Water Supply and Distribution
The hydrology behind the water supply and distribution for the Villa d’Este gardens allowed engineers to overcome major challenges in fluid mechanics to create impressive water displays. The fountains in Villa d’Este are supplied with water through the River Aniene. River Aniene is located north of the gardens, as shown in Figure 12, and is derived from two mountain springs. The river flows from the Simbruini Mountains to pass through Tivoli, the location of Villa d’Este. It ultimately feeds into the Tiber River, which runs through the city of Rome .
The topography of the gardens was the main challenge in water distribution for Villa d’Este. The gardens are heavily sloped, with a total elevation change of over 45 meters. As a result, canals were designed to carry water to the pools and fountains; water is distributed from the River Aniene to Villa d’Este through canals totaling 875 meters in length. In addition, pipes totaling over 200 meters in length were used underground throughout the gardens .
Gravity was used to feature the water in the fountains, so the layout of these pipes was key in order to achieve such a display of water. The large slopes of the gardens also enabled the fountains to function using gravity to create large sprays of water . Mathematically, this is represented by the energy equation for steady, incompressible flow shown in Figure 13, which demonstrates the conservation of energy for the flow. For the fountains of Villa d’Este, this equation can be reduced to the equation shown in Figure 14 because the pressure of the water is zero at the nozzle tip and at the higher elevation. Ultimately, this shows that decreasing the height of the water will increase its velocity, allowing for the grand water displays of the large fountains at Villa d’Este. This equation also accounts for head loss, which can be divided into major or minor losses. Major losses are a result of shear stress on the water by the pipe, and minor losses are a result of changes in the flow field, such as bends in the pipes. These head losses were important for the water engineers to overcome in order to ensure that the water would display from the fountains. While the water engineers did not explicitly use this energy equation, they utilized the concepts behind the equation of converting changes in elevation to velocity for the flow of water, while accounting for energy loss due to friction or turbulence. This was particularly challenging for fountains with lower changes in elevation.
These equations assume that the pipe flow is steady and incompressible. Under normal conditions, water can be assumed to be incompressible, and so this assumption is appropriate here . In addition, steady flow can be assumed using the concept behind the Reynolds Number as shown in Figure 15. The Reynolds Number is the ratio between viscous forces and inertial forces, and a small Reynolds number signifies laminar, or steady, flow. It is reasonable to assume that the flow in the pipes at Villa d’Este is steady because the velocity of the water was likely low, particularly as no pumps were used in the system. A lower velocity results in a lower Reynolds Number, signifying that it is appropriate to assume that the flow of the water through Villa d’Este was steady for the use of the energy equation above.
The Villa d’Este fountains represent an example of water engineering which signals wealth and status. The understanding of fluid mechanics in order to overcome challenges with energy, small elevation changes, and head loss in addition to the high cost of construction in material and labor were integral factors in establishing the gardens. These prices and the end product of major water displays spanning d’Este’s estate illustrate the major costs of construction and its implied wealth and status.
While this article focuses on two major examples of water features in Rome, there are hundreds of other displays engineered from ancient Rome to post-Renaissance. Many of these water features exemplify how water displays signal wealth, status, or prosperity for Rome, whether it be for individuals such as d’Este through his villa and the popes through the Trevi Fountain or for the civilization itself. Pictured in Figure 15 is my personal favorite fountain in Rome, which represents another scale at which the Romans demonstrated their knowledge of water engineering. Roman engineers were experts in hydrology, and many of their impressive designs are still used today, including Aqua Virgo – with the help of several rounds of repairs. These engineers worked without many modern technologies, and the engineering behind the water displays – including major construction undertakings, the use of expensive materials or detailed art, and the reliance on gravity for large fountains – highlight the wealth and status required for these designs to have come to fruition and remained functional today.