Water, left to its own devices, always flows from its highest point to its lowest, until the two points are on the same level. If a canal sloped as it climbed a hill, its water would simply flow to the bottom. One solution is to bore a tunnel through the hill, so that the canal can continue on a level course, but sometimes this is too costly or geologically impossible. Building locks can solve this problem.
Canals are waterways channels, or artificial waterways, for water conveyance, or to service water transport vehicles. They may also help with irrigation. It can be thought of as an artificial version of a river.
In most cases, the engineered works will have a series of dams and locks that create reservoirs of low speed current flow. These reservoirs are referred to as slack water levels, often just called levels.
A canal is also known as a navigation when it parallels a river and shares part of its waters and drainage basin, and leverages its resources by building dams and locks to increase and lengthen its stretches of slack water levels while staying in its valley. In contrast, a canal cuts across drainage divide atop a ridge, generally requiring an external water source above the highest elevation.
Many canals have been built at elevations towering over valleys and other water ways crossing far below. Canals with sources of water at a higher level can deliver water to a destination such as a city where water is needed. The Roman Empire’s aqueducts were such water supply canals.
Caen Hill Locks are a flight of 29 locks on the Kennet and Avon Canal, between Rowde and Devizes in Wiltshire, England. The 29 locks have a rise of 237 feet in 2 miles (72 m in 3.2 km) or a 1 in 44 Gradient. The locks come in three groups: the lower seven locks, Foxhangers Wharf Lock to Foxhangers Bridge Lock, are spread over 3?4 mile (1.2 km); the next sixteen locks form a steep flight in a straight line up the hillside and are designated as a scheduled monument. Because of the steepness of the terrain, the pounds between these locks are very short. As a result, fifteen of them have unusually large sideways-extended pounds, to store the water needed to operate them. A final six locks take the canal into Devizes. The locks take 5–6 hours to traverse in a boat.
A lock consists of two gates across the canal, with mechanisms for opening them on the towpath.
To climb to a higher level of the canal, a boat enters the first lock gate, which is closed behind it.
Paddles in the second lock gate are opened so that water can flow in, gradually raising the level of water in the lock.
When the water ahead is level with that in the lock, the gates are opened and the boat can move on.
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