Israel is, I believe, the place in the world that has the most desal,
and is actually already using it for ag. I'm not familiar with domestic/development policy in Israel, but I have trouble believing it's as restrictive as the CA. So not only has CA not already done it, but neither has Israel, who, at the very least must have
different roadblocks.
The point is, it's not only California (which I agree is pretty anti-development and where this plausibly might be disallowed even if it did make economic sense) that is leaving this supposed $100 bill on the ground.