Gravity is a conservative force, so if you raise something up really high, dropping it will recover the energy used to pull it up. Of course in practice there's a lot of other things that cause energy loss, but there are lot of dams in the world that exist as "stored power", by pumping water uphill, then getting energy back as the water goes through the dam later.

Big bucket high up is basically a battery. The question then becomes about the details of, like, using the power when the water gets pumped down (if you had two canals, you could probably time filling one with draining the other?). There's a lot of practical things to consider

You pump the water out of it into a reservaour, than later on when you need to fill it, you let it run back and generate energy.

Water power efficency is about 80-90%

There is a nice video (Practical Engineering) that covers this very well. https://www.youtube.com/watch?v=SBvclVcesEE

Imagine one ship going upwards in a lock, while another goes down. Ships and locks are the same size.

To start with, there is a difference in the water levels - and this can be put through a generator to generate electricity as the water flows from one lock to the other.

When the water has moved half way, the levels are equal. You can now use electricity to pump the rest of the way - and theoretically, assuming lossless pumps and generators, you use the same amount you generated earlier.

Unfortunately, low-head generators tend to be inefficient and expensive. Variable head generators are even harder to design to be efficient.

One way is like this: https://en.wikipedia.org/wiki/Falkirk_Wheel No water is used up. Virtually no energy is needed either, except to overcome friction. But scaling it up to the size of the locks on the Panama canal would be huge.