How Do Boat Locks Work?

Boat locks work as a sort of "water elevator" to raise ships to higher elevation. This is often necessary in areas near dams or rapids, where the water level on a waterway changes dramatically.

In a boat lock, the "lock chamber" has two gates, one at either end. These gates can be opened and closed when needed. When a boat needs to be lowered, it enters the lock chamber. The far gate is closed, stopping the water from rushing out.

Once the boat is between the gates, the near gate is also closed. The boat waits in the lock chamber.

Next, the boat must be lowered. Large valves are opened, which let water drain from the lock chamber toward the low water level. The water between the gates slowly goes down, lowering the boat with it. Because both gates are closed, the boat stays in place. Ropes are used to keep the boat steady as it lowers.

Once the water level in the lock chamber is even with the bottom portion of the waterway, the far gate is opened. The near gate stays closed, holding back the water and acting as a temporary dam. The boat exits the locks and continues its journey.

For traveling the opposite direction, the process is reversed. Instead of being drained, the lock chamber is slowly filled with water with both gates closed. Like an elevator, the rising water lifts the boat to higher elevation.

References

• EPA Information on Locks and Dams
• Lock Operation - Soo Locks
• Boat Lock Details