The Surprising Efficiency of Canal Locks

They do pump water out and back into the locks from neighboring storage. There is a limit to the minimum amount of water that you can use, though, since the potential energy to raise the ship comes from the loss of water. ▶ this video

> without saying anything about which one is used how and where I agree that it is strangely edited. But to help you out with the info: both are used on the Panama canal. There are two paralel sets of locks, the older ones and a more modern ones. The more modern ones can fit a bit bigger ships and they are more efficient with water. This is a wikipedia page about the expansion project (the one which also constructed these more modern locks): link And here is a video on how one can construct a “water saving lock” from Practical Engineering: ▶ this video

I enjoyed this well made video illustrating how it works: link And this one explaining how reservoirs can be used to trade-off water consumption for land requirements using side ponds: ▶ this video

For anyone interested in how the new (bigger) locks use less water than the old locks (reclaiming 60% of the water - without pumps!), this old Practical Engineering video explains with diagrams: ▶ this video They store the water in a series of basins at different levels, and use those basins to fill the portion of the lock below. It's more obvious with diagrams.