There's a lot of recycled water being applied to golf courses in SoCal and I think in Arizona as well. This can require dedicated new pipelines if the water doesn't meet drinking water standards, which are getting more strict all the time. The new pipelines can add a lot of cost. If they treat it to drinking water quality, then they can mix it into the established distribution system without new pipes.
Back to Ken's main point, there's only so much rain that falls in SoCal, and it gets contaminated as it travels the stormwater system, so the numbers don't add up for full "water independence" in today's society. Eventually, conservation efforts hit a point of diminishing returns (we still have a lot we can do to conserve) and population growth becomes the critical factor. No harm shooting for this as a goal and getting as close to it as possible, but don't lose credibility along the way. SoCal will need to import and store large quantities of water for the foreseeable future. They're getting smarter about it all the time.
