How Aqueducts Work

Potable (drinkable) water and water in general is one of the most precious substances on the planet because every living thing needs it to survive. Not every area of the world has access to water or enough water to support the needs of a growing population. Aqueducts are one method of transporting water and potable water that have been in use since around 300 BC. Aqueducts are structures that are capable of transporting water across a long distance to where it is needed but how exactly do they work?


An aqueduct is a man-made water conveyance structure that has been around for quite some time. The materials for an aqueduct range from clay, to brick, concrete, or metal piping and have changed over the course of the aqueducts’ usage. The source of water was and still is from rivers, underground springs, groundwater, wells, and dams. Water transported to its destination could be used for a variety of different uses such as irrigation, sanitation, and also for human consumption. There are several different types of structures that bear the name aqueduct and all perform the same basic function. The Romans were the first to use this kind of structure; it resembled a bridge with numerous arches and was made from rock. Instead of transporting people, it transported water to areas that needed. Aqueducts can also be open or closed channels that are basically man-made streams transporting the water. The channels are along the ground though, not raised like the ones the Romans used. Some extremely large modern aqueducts have even been used by ships as something similar to a canal. The final type of aqueducts consist of underground tunnels and channels that transport water in the same way as their above ground counterparts, but are never seen.

Movement of water

The basic principle behind how an aqueduct works is gravity. Water will naturally flow from an area of higher elevation to an area of lower elevation and the aqueduct merely provides a pathway. The structure mimics an actual stream in some ways and will gradually go downhill until the water reaches where it is meant to go. The incline for the aqueduct is usually incredibly slight at around 1% but can range from 0.5-2%. Romans typically used a 1/200 (0.5%) incline meaning that for every two hundred horizontal length units of the aqueduct, the height of the surface of the water went down by one vertical length unit. Because this slight incline was kept throughout the structure, water would naturally travel through the aqueduct without being impeded or stopped, usually along a straight line towards the destination.

Whereas this might work in some areas, the transportation of water isn’t always as simple as moving downhill. Sometimes the source of water is actually lower than the destination, or the terrain may drastically change along the way. The Romans were only able to partially solve this problem with their aqueduct structure. The terrain could change, but the structure would leave the water elevated above the terrain and the structure would change in height to compensate and keep the same incline present throughout. When faced with a large hill they might make a runnel for the water to travel through. The water could not, however, go uphill, unless it was a result of its own speed and pressure that would force it slightly uphill. Therefore the Roman aqueducts could only be constructed where the right conditions existed.

Today however, the water can be moved uphill by pumping stations and an aqueduct can go from its source to its destination no matter what the terrain. These stations will force the water uphill in many areas and keep the water moving despite the terrain and elevation. The aqueduct systems of California make use of these pumping stations to keep water moving through the many miles of channel that they use. In this case, the channels just run along the surface and the terrain can even be altered to make a better path for the channel. There are also water treatment plants that can ensure the water is safe for drinking and aqueduct systems may feed into a treatment plant at some point.