The British Dam Society
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About Dams

Back to usesUses for Reservoirs - Navigation

Ship lock

One of the ship locks in
operation at Gezhouba Dam
on the Yangtze River in China

The construction of a dam across a river forms a reservoir that raises the water level upstream, stores the water, and slows down its rate of flow. This improves the navigation conditions upstream of the dam for ships and boats. Dangerous areas of rocks and sandbanks, previously in shallow water, become well covered, and rapids in the river disappear. Also, water from the reservoir can be released into the river downstream during the drier seasons of the year to make sure that it is deep enough for navigation all the year round.

A dam forms a barrier to any shipping, so navigation locks (similar to the canal locks in Britain) can be constructed to one side of the dam, or special lifts can be built into the dam for raising and lowering vessels.

Model of the Three Gorges DamModel of the Three Gorges Dam with ship lift and ship lock

A ship lift and a navigation lock are being provided in the Three Gorges Dam which is currently being constructed across the Yangtze River in China. The ship lock will have two channels each 1.6 kilometres long. There will be five steps in each channel to raise and lower vessels over a maximum height of 113 metres.