Aqueducts

DEFINITION: Artificial waterways constructed to move water from one area to another

Human beings’ redirection of water from one area to another through aqueducts can have numerous environmental effects. Ecosystems on both ends of an aqueduct are influenced by the reduction or increase in available water, and the building of aqueducts often involves the disturbance of what was formerly pristine land.

Sufficient water is an absolute necessity for all forms of life on earth (both plants and animals); this fact dictates that life-forms in areas that receive insufficient precipitation or that are not near lakes or rivers must either migrate to more favored regions to survive or develop techniques to bring water in from more favored areas. Certain xerophytic plants (such as cactus) and animals (such as the kangaroo rat and the jackrabbit) manage to survive on minimal amounts of water, but they are exceptions; most species need abundant supplies of water. Over time, human societies have either adopted the migration alternative or developed techniques to import water into drier areas by building conveyance devices. The artificial waterways known as aqueducts date back several thousand years; they have allowed human settlement and agriculture to flourish in several regions.

Ancient Water Delivery Systems

The Minoan civilization, with its capital of Knossus on the Greek island of Crete in the Mediterranean Sea, represents the earliest known record of the development of water-supply infrastructure. Aqueducts were used to bring water into the city about five thousand years ago, until a major earthquake sometime around 1450 BCE destroyed the region. The next major development in the building of aqueducts occurred circa 1000 BCE, when underground tunnels called qanats were used in the Middle East and North Africa to bring water from upland sources to villages and local farms. Modern-day Iran has the largest number of qanats in the region (more than twenty-two thousand), with lengths that vary from 40 to 45 kilometers (25 to 28 miles) and depths approaching 122 meters (400 feet).

The ancient Romans were renowned for their extensive system of elevated stone aqueducts beginning about 312 BCE. By 300 BCE, Rome had fourteen major aqueducts in service, bringing to the city about 150 million liters (roughly 40 million gallons) of water per day. Major water-supply systems were also built in those parts of Europe that were within the Roman Empire at that time, including what are now Italy, France, Spain, the Netherlands, and England. In Segovia, Spain, an aqueduct that was presumably built in the first century CE by the Romans is still being used.

In North America in the ninth century CE, the Hohokam built canals that were 9-18 meters (30-60 feet) wide to transfer water from the Salt River, near present-day Phoenix, Arizona, to local farms for irrigation. In the tenth century, the Anasazi developed a similar type of scheme in what is now southwest Colorado. During the fifteenth century, the Aztecs used rock aqueducts to supply both drinking water and water for irrigation to the area of present-day Mexico City.

Modern Aqueduct Systems

As might be expected, modern water-delivery systems use some of the same techniques that were used successfully in ancient times. For example, modern systems, like ancient ones, make use of gravity to move water along as much as possible. Increased populations and the accompanying increased demand for water, however, require modern designers of aqueducts to employ additional techniques. Modern aqueducts must often transport water over great distances from the sources to the consuming populations, and conflicts sometimes arise when water is withdrawn from one area to serve another. Electricity or turbines are used to power huge pumps that can move water long distances. In some areas, the use of underground conduits is necessary to avoid interference with street traffic.

In 1825 the completion of the Erie Canal between Buffalo, New York, and New York City encouraged the export of agricultural products from the American Midwest to Europe and led to an increase in for New York City. Since the Hudson River was too salty to use as a supply source, the city started work on a and aqueduct in the Croton River in Westchester and Putnam counties. The project was finished in 1842 with a capacity of 341,000 cubic meters (90 million gallons) per day, an amount that the planners thought would be sufficient for a future city population of one million. New York continued to grow, however, necessitating expansion during the early twentieth century into the Catskill and Delaware watersheds and the construction of six new reservoirs and connecting aqueducts. The overall system now serves some nine million people with an average daily consumption of 4.5 million cubic meters (1.2 billion gallons) per day.

In contrast to New York, which receives average annual precipitation of 1,067 millimeters (42 inches), the Los Angeles metropolitan area receives about 381 millimeters (15 inches) of precipitation per year. The first project to bring in outside water to Los Angeles began in 1907 with the construction of an aqueduct 375 kilometers (200 miles) long, from the Owens Valley in east-central California, a project that was initially met with stiff from Owens Valley residents. The next major undertaking for Los Angeles was the Colorado River Aqueduct Project, which was started in 1928 under the sponsorship of thirteen cities in Southern California that formed the Metropolitan Water District (MWD). By 2010, the MWD consisted of twenty-six water districts and cities and was responsible for supplying drinking water to an estimated population of eighteen million, with an average delivery of 7 million cubic meters (1.8 billion gallons) of water per day.

Other major projects to transfer water in arid to semiarid regions of the United States include the Central Arizona Project, which was authorized in 1968 by the US. Bureau of Reclamation. Construction started in 1973 to convey water from the Colorado River at Lake Havasu on the Arizona-California border to central and southern Arizona. The delivery system is 540 kilometers (336 miles) long and includes fourteen pumping plants and three tunnels. This is one prominent instance where huge amounts of power are required to overcome gravity, as the elevations at Lake Havasu, Phoenix, and Tucson are 136 meters (447 feet), 458 meters (1,503 feet), and 875 meters (2,870 feet), respectively.

Bibliography

Arevalo-Perez, Alexis. "From Mountains to Found: Rome's Aqueducts." Engineering Rome, 1 Nov. 2022, engineeringrome.org/from-mountain-to-fountain-romes-aqueducts/. Accessed 12 July 2024.

Cech, Thomas V. Principles of Water Resources: History, Development, Management, and Policy. 3d ed. New York: John Wiley & Sons, 2010.

Hillel, Daniel. Rivers of Eden: The Struggle for Water and the Quest for Peace in the Middle East. New York: Oxford University Press, 1994.

Koeppel, Gerald T. Water for Gotham: A History. Princeton, N.J.: Princeton University Press, 2000.

Moul, Dr. Russell. "How Did Ancient Romans Build Aqueducts?" IFLScience, 28 Aug. 2023, www.iflscience.com/how-did-ancient-romans-build-aqueducts-70421. Accessed 12 July 2024.

Powell, James L. Dead Pool: Lake Powell, Global Warming, and the Future of Water in the West. Berkeley: University of California Press, 2008.

Strahler, Alan. Introducing Physical Geography. 5th ed. Hoboken, N.J.: John Wiley & Sons, 2011.

Yoksoulian, Lois. "The Marvel of the Roman Aqueducts." University of Illinois Urbana-Champaign, 17 Aug. 17, 2022, las.illinois.edu/news/2022-08-17/marvel-roman-aqueducts. Accessed 12 July 2024.