How Aqueducts Work

An aqueduct is a man-made water conduit used to channel water from the water’s source to the water’s destination. The design of the aqueduct is based solely on the principle of gravity flow. Have you ever wondered how aqueducts work?

An engineer who specializes in water based projects uses an instrument to determine the gentle, downward slope that the water will travel from its point of origin to its point of destination. In this way the engineer and contractors will be able to determine where the path that the water needs to flow such as below ground in tunnels, or on the surface in trenches that are covered. If there is an area of ground that needs to be spanned, such as a valley, then it will be determined the need for pressurized pipes, walls or arcades.

It is essential that each and every step in the aqueduct’s building process be carefully planned in order to insure that gravity flow of the water makes its way gradually to its point of destination. This is important because if the downward slope is too steep, the water will flow much too quickly, coming to its point of destination with great explosive force.

Understanding the different rudiments of an aqueduct, and how each one works, will help you to better understand exactly how an aqueduct works; providing water to parts of the world that would otherwise not have water.


When an aqueduct follows the outline and form of the land, then a trench is used. It is basically a lined ditch, built with a gradual slope. It is relatively quick to build, not taking a lot of time.


Sometimes in building an aqueduct, it is necessary to build tunnels through hills and mountains to run the water through. Though this encompasses some work and expense, it does save having to build trenches around the mountain.


A wall is used for the water to flow on top of when there is a shallow valley or depression in the landscape. A wall is not ideal if it need be too high or long, because it impedes the natural flow of nature, people and water.


An arcade is necessary when the aqueduct must span high areas such as valleys. Built with a series of arches, they take less building material than building a wall. Not only does it make a beautiful structure to look upon; an arcade does not impede the flow of nature, people or water from the ground below.

Pressurized Pipes

Did you ever wonder how the ancient civilizations such as the Romans were able to get their aqueducts up and down high valleys without the use of pumps? On really high valleys, the use of arcades would not be practical because they would have to be built too high, making them unstable. Instead they used pressurized pipes, or inverted siphons. The water would travel down pipes on one side of the valley, and then the water’s force would push it back up the other side. The height at which the water exited these pipes would be just under the height at which it entered.

Understanding how the different components of an aqueduct work when put together helps one to understand how they work as a whole when put together as an aqueduct.

Julius Frontinus (ca. 40 – 103 AD) was appointed Water Commissioner of the Aqueducts (curator aquarum) in 95 AD. During this time of service he wrote two books called De Aquaeductu. They were an official report to the emperor on the state of Rome’s aqueducts. Their history, as well as their description and how they work, are included. Not only is this work interesting from a historical standpoint, but the reader is truly given a working knowledge of aqueducts.