[skybrian]

Sort of. There are California cities that already have desalination plants. It's okay for retail users on the coast (who are okay paying a bit more).

Agriculture is different. They rely on much cheaper prices and besides, you'd have to transport it uphill.

[logfromblammo]

That reminds me of the old engineering joke.

What's the best way to transport a million kg of water? Build a cloud.

If you're thinking statewide, you could just evaporate seawater, and it's eventually going to rain out somewhere in the mountains.