Well put. 80 percent of the developed water supply in California is used by agriculture. About 6 percent is industrial and commercial. That leaves 7 percent residential landscaping, and 7 percent residential non-landscaping (showers, washing machines, etc.). Source: http://www.kcet.org/updaily/socal_focus/commentary/where-we-...
Even if residential landscaping water usage dropped by a quarter immediately, which seems rather unlikely, that's close to a rounding error compared to the amount of water to turn our near-desert into an agricultural breadbasket. Put another way, more water is used for almond farming in California than all residential landscaping or residential non-landscaping: http://www.slate.com/articles/technology/future_tense/2014/0...
But instead of addressing the 80% problem, and the fact that some cities like Sacramento still don't have everyone on metered water* (it's unlimited! flat rate! use as much as you like!), we'll have hydrotheater restrictions on drinking water at restaurants. Hydrotheater is, of course, a cousin of TSA-style security theater, and approximately as effective.
* Water meters won't even be fully installed by 2025. http://portal.cityofsacramento.org/%20Utilities/Conservation...