How do Canal Locks Work

Canal locks have been around for centuries, and are both elegant yet ingenious.

In the early days of canals, locks were not necessary. Engineers built them on flat land; gradients were not an issue. However, canals are man-made structures originally designed for work, not pleasure. To make best use of them, they needed to go where the factories were – hills and all.

Locks were invented to let boats travel up and down gradients on water. They work like an ‘aqua lift’; the boat is enclosed in a chamber, which is either filled with or emptied of water. This commonly carries the boat up or down a height change of several metres.

Where there is a steep gradient to climb, there are numerous locks spaced across the gradient. These can either be individual locks separated by a lock-free waterway, or a ‘staircase’ – these are faster as the ‘upper’ gate of one lock is the ‘lower’ gate of another.

Each lock cycle involves the transfer of many tens of thousands of gallons of water. On artificial canals, it is important this water flow is managed to ensure the canal does not run dry. Luckily, the historic engineers considered this too, ensuring even Victorian lock systems work as well today as they always have.