Abstract
The Segovia aqueduct is one of the most exceptional displays of roman hydraulic engineering to date. Constructed using masonry stones and with no mortar, the aqueduct has survived centuries and had been in use until mid-20th century when it stopped being used. Engineers today are applying some of the knowledge they learn from to develop stable structures. However, to develop such a structure in modern day a lot of work, engineering computations, machinery and skill are required.
Introduction
The Roman culture at the time involved owning slaves. The slaves included Greeks who were captured as the Romans invaded Greek lands. Additionally, a government collected fees and taxes from residents. This money was used partly in the construction of infrastructure such as roads and aqueducts. The Segovia Aqueduct can be found in the small city of Segovia. The aqueduct is one of the most celebrated treasures in the city. During the Roman Era, the roman population was increasing at a high rate and the emperors at the time focused on increasing their territories by conquering new areas. In these new areas, water was a prerequisite for the Romans to live. Therefore, the emperor had to look for ways of distributing waters from the mountainous areas to the people. The water distributions system supplied water by gravity. In Rome, there were several built aqueducts prior to the construction of the Segovia aqueduct in Spain. This prior knowledge in aqueducts contributed significantly towards the construction of the Segovia aqueduct. The Segovia aqueduct is over 800 meters long and its highest point towers 30 meters above the Plaza de Azoguejo. The aqueduct was constructed to convey water from spring Fuenfria located about 15 kilometers from the city. The water first was collected in a tank known as El Caseron before being transferred to a second tower referred to as Casa de Aguas or a water house. Here the water was allowed to decant before being allowed to flow in its route. The gradient of for the water flow was kept at 1% until it reached a rocky outcropping near Postigo where the aqueduct was built. At the Plaza de Diaz Sanz, the structure has an abrupt turn and heads toward Plaza Azoguejo. The aqueduct can be seen as a series of supports that varies in height depending on the number of stories and contour of the land. Once the structure enters the city, its full height can be seen and it has a foundation that is almost 20 feet deep. The structure consists of 75 single arches and 44 double arches. The roman engineers names involved in the construction of the aqueduct have their names displayed in bronze letter signs on the tallest arches. Additionally, the date of construction is indicated. This was during the Roman era.
According to Baskett and Guide (150), the aqueduct was constructed without any mortar or cement at the end of the first century AD. The exact or specific time is not known, but some believe it to be 50 AD. It was constructed during the reign of Roman Emperor Augustus. However, some literatures claim that it was constructed during the reign of Trajan. However, it has stopped carrying water from Rio Frio to the city. According to Whitney (72), the stones of the piers are large, are about two feet by four feet by two feet in size, and are placed in regular courses. At this time, the Romans were some of the great builders of bridges and pioneered most of the engineering technology at the time. Most of the civilization can be evidenced by the structures in Rome that are still standing. The Segovia aqueduct was functional until the middle of the 20th century when it stopped being used. Additionally, during this era the Romans were involved in slavery, which was their main source of labor for their engineering and construction projects. Roman science at the time was little and was largely influenced by the Greek philosophers and scientists. Kleiner (91) asserts that Segovia aqueduct construction was largely due to the unfavorable terrain at the time. Romans preferred to build their conduits underground. This ensured or reduced the risk of their enemies contaminating their water supply systems. Additionally, the construction of the aqueduct was necessary for the maintenance of the gradient for water supply. In order to maintain the gradient of the conduit, the Romans decided to incur cost and risk to develop the 800-meter aqueduct.
Figure 1: Segovia Aqueduct. Source Engineers Photo journal
Construction of the Segovia Aqueduct
According to Krebs and Krebs (139), the material used in the construction of the Segovia aqueduct consisted mainly of masonry (stone, bricks and mortar), lead or bronze piping, and earthen piping. Masonry was highly used to due to its high availability. The construction of Segovia aqueduct consisted of a row of double arches that had large square stones placed together without the use of cement or mortar (Krebs and Krebs 139). The channel for the water having walls on each side was constructed above the square stones using large oblong flat stones. An approximate 20,400 blocks were used and their stacking was unique in that they were able to produce stability without using any mortar.
For the construction to be carried out a surveyor was required to map out the unfamiliar and sloping hillsides. The surveyor had to determine the most suitable location of the aqueduct depending on the height of the slope. The surveyor used different equipment to make evaluations and come up with final decisions about the direction the construction would take. One of the equipment used was the dioptra, which was an upright distance sight level that had limited capability (Krebs and Krebs 140). Additionally, the surveyor had a leveling staff that was used together with the dioptra to establish the horizontal line of sight. Further, chorobates, equipment used by the surveyor had a long narrow beam like device. The device had a water channel, which was used to establish whether the actual construction on the ground was level as per the design requirements or standards. Engineers ensured that the arrangement of the layers of stones was done appropriately and the lining of the water channels was correct.
The manual labor involved in the construction of the aqueduct was intense and most of the freed men would not agree to working in such conditions. Thus, the main the labor force for the construction of the aqueduct mainly consisted of slaves. A slave was put in charge of the other slaves in the construction and was referred to as a foreman. Duties of the foreman included organizing the slaves and signing tasks that provided by the Roman engineers. Numbers of laborers reached hundreds. The cost of slave labor was high as the slaves were expensive to purchase thus most of the construction work used to hire slave labor. This contributed to increasing the construction cost of the aqueduct.
Method of construction of the Aqueduct
Prior to the construction of the aqueduct, the Roman engineers had to locate the source of the water. Mostly, the engineers used to obtain water from springs and had to determine the water quality first (Aicher 7). The engineer had to inspect the clarity, taste, and flow of the water. The soil and rock types gave an indication of the quality of the water. For instance, presence of clay soils indicated the quality of water to be poor since the water would be scarce and distasteful, whereas water obtained from red tufa was pure and abundant. Additionally, the presence of water loving plants such as the alders and willows indicated the presence of water beneath them (Aicher 7). Once the engineer was satisfied, that the water source was good, a pit was dug, and the flowing water directed to feeder channels. Conduits used by the romans were open channels, lead pipes, and earthenware pipes. For the Segovia aqueduct open channels were used and were built from arrangement of masonry stones.
Once the water source was identified, the engineers or the surveyors at the time had to establish the best route that would ensure water flow by gravity. Additionally, the engineers had to follow a similar aspect used in the construction of Rome’s aqueducts. This was the use of gravity for water flow. According to Aicher (7), the steep gradients were avoided as they caused the erosion of the walls of the water channel and threatened the stability of the aqueduct. Using the chorobates, the engineer placed water in the small water channel on top of the beam and adjusted the beam to the level of the water. Consequently, using this level the engineer projected a horizontal line to a marker placed at a distance.
The construction of the aqueduct also took into account the application of water treatment. There was presence of settling tanks at the end of the aqueducts, which allowed for the decantation of sediments. Additionally, the movement of the water on the aqueducts provided aeration of the water.
Design of the Modern Aqueduct
One of most important factors in designing an aqueduct such as the Segovia aqueduct is the economic aspect. The Segovia aqueduct was an expensive project at the time for the Romans. Based on engineering principles an aspect that engineers seek to achieve in the design and construction is economic efficiency of the structures. In the modern world, the construction of such an aqueduct would require the use of cement, which is an expensive material. Additionally, the likely maintenance costs of the aqueduct would also have to be taken into account. This would result from the cases of sediment removal from the water channels. Consequently, the purpose of the aqueduct will have to be established whether irrigation or water supply. This will be used in the determination of either open channel flow or pipe flow.
Furthermore, labor used would involve a variety of professions. Use of slave labor would not be used as it is violates human rights. Safety of the laborers would have to be taken into account. That would include the availability of safety equipment and proper housing for the laborers on site. In the construction of the Segovia aqueduct, the engineer or the surveyor was the main person involved in ensuring that construction was done according to plan. Currently, such a construction would require a team of engineers, surveyors, and contractors with skilled labor and machinery and equipment. Cranes and earthmoving machinery would be used. The equipment used would be more because of the different earth preparations required for the foundation and making of concrete. In the team of engineers, a geotechnical engineer who would specialize in the investigations of the soils for foundation of the aqueduct. A structural engineer would be involved in the preparation of structural drawings and reinforced concrete design to use for the structure.
Massive investigations would have to be carried out, which would involve earthquake investigations and wind conditions of the site. Seismic analysis would involve longitudinal and transverse seismic analysis. Additionally, the investigations would have to establish the ability of the foundations for the aqueduct to resist permanent ground deformations. In cases where the soils or site of proposed construction is subject to liquefaction, an additional vertical bearing support will have to be provided beyond the liquefiable layers of the soil. Piped connections will be recommended to reduce contamination of the water.
Environmental impact assessment of the proposed project would have to be conducted. In the current world, preservation of biodiversity is essential and thus there would be potential loss of animal and plant species. Such an evaluation would ensure preservation of biodiversity.
Unlike for the Segovia aqueduct, hydrological considerations would have to be evaluated. An estimate of the required discharge capacity of the channel would have to be established to ensure that the design of the aqueduct is sufficient to support the water channel carrying the discharge. Peak discharge estimates from the daily flows will be used to design a safety system. Additionally, reservoirs and cisterns would be introduced to regulate the flow of water. These regulatory structures would help prevent overflows and unnecessary aqueduct operations in during rainy seasons. Flood estimates in the area would be used in structural design to ensure the aqueduct piers can handle the maximum force of the expected floods.
If the construction of the aqueduct will pass through a town or will cause displacement of people, alternatives locations for their transfer would need to be identified and compensations made accordingly. A work schedule would be developed and different expected milestones set to ensure the project is completed within the required project duration. This would aid in reducing avoidable increases in costs. After completing the initial survey work, construction would begin upstream with the major concrete works to start as early as possible.
Conclusion
Based on the information discussed, the construction of the Segovia aqueduct was an expensive and difficult task. For engineers today, such a construction involves numerous hydraulic and structural computations. Some of the knowledge that the Roman engineers applied may be limited today and achieving such quality constructions may be a difficult task despite the increase in technology. Most importantly, the design of such a structure depends on the engineer’s judgment and assessment of how the structure will respond to the loads it carries. Because of the different flow requirements in the construction of the aqueduct, engineers today need to involve hydrological experts who will guide in the design to attain safe operation of the aqueduct system during the rainy seasons. Additionally other important aspects in the engineering and construction of aqueducts include geotechnical engineering, surveying, water management, and structural engineering.
Works Cited
Aicher, Peter J. Guide to the Aqueducts of Ancient Rome. Wauconda, Ill: Bolchazy-Carducci, 1995. Print.
Baskett, Simon. Madrid: Directions. New York: Rough Guides, 2004. Print.
Krebs, Robert E, and Carolyn A. Krebs. Groundbreaking Scientific Experiments, Inventions, and Discoveries of the Ancient World. Westport, Conn.: Greenwood Press, 2003. Print.
Kleiner, Fred S. A History of Roman Art. Boston, MA: Wadsworth, Cengage Learning, 2010. Print.
"Roman Aqueduct at Segovia, Spain." Comparative Technology Transfer and Society 7.3 (2009): 2-2. Project MUSE. Web. 22 Nov. 2013. http://muse.jhu.edu/
Whitney, Charles S. Bridges of the World: Their Design and Construction. Mineola, NY: Dover Publications, 2003. Print.
