This is a very interesting/amusing idea. Unfortunately, moving substantial quantities of water would be very difficult. I'm presuming you are joking about this proposal.
I live in a house with a cistern. We transport all our water in a tank wagon from a few miles away. It's not very difficult or expensive.
I think we need a discussion thread for the californian drought going on. I would like to compile information in the main post and would like help compiling it. If we really are proud to be effective altruists then this is an area we should really figure out.
Any one have any good ideas on how we can help?