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Why must lock gates withstand pressure from different water levels?

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View of Utrecht's Oude Gracht canal lined with historic brick buildings, arched doorways at water level, and boats moored along the canal edge in the Netherlands. — canals and inland waterways The *Oudegracht* (Old Canal), Utrecht, Netherlands.

Lock gates must be strong enough to withstand water pressure because they serve as movable barriers that separate adjacent pounds (basins) within a lock system. These pounds often exist at different water levels to facilitate the raising or lowering of vessels.12

When the gates are closed, the difference in water height between the two sides creates significant pressure against the gate structure. To manage this, gates are engineered to resist these forces effectively. For instance, miter gates are designed to meet at an angle pointing upstream, which allows the force of the water to help keep them securely closed. Because of this pressure, most gate types—particularly miter gates—can only be safely operated once the water levels on both sides have been equalized.132