My solution is: They've got those big ponds where they can somewhat reuse some of the water. Practical Engineering has a video on it (That's the channel with that guy, Grady, right?) Okay, cover those with solar panels. 1: Less evaporation from there because the panels will block the sun and keep them cooler. 2: energy to run some pumps to at least partially pump some water uphill so less is lost when lowering the outermost locks.

The big brain am winning again. I am the greetest! Now all we need is the umpty frillion dollars to build it.