SierraNevada - Glad to hear that Sacramento is practicing xeriscaping. I believe the annual rainfall there is about 20". The upper Mojave, Ridgecrest/Inyokern specifically, gets a quarter of that, and in some years less than 10% of that. The upper Mojave is on the margin of the Great Basin, a large area of arid or semi-arid climate. When you consider that at least 3 large metropolitan areas - Las Vegas, Salt Lake and the Los Angeles megalopolis depend in part on this area for their water supply makes you scratch your head.
