The canal climbs to a lake twenty-six meters above the sea, and ships can't climb hills.
- So you build a lock: a concrete chamber with gates at both ends.
- But now you have to lift tens of thousands of tons.
- So you open a valve, and lake water rushes in through tunnels in the walls. No pumps, just gravity. The ship floats up.
- And for a tall hill, locks in a row make a staircase. Three steps lift ships the whole twenty-six meters.
- But every crossing through the old locks pours about two hundred million liters of fresh water into the sea.
- So newer locks drain into basins beside the chamber, and reuse sixty percent of it.
The ship never climbs at all. Falling water lifts it, one step at a time.
