California, with the exception of some agriculture, can survive mega-drought by reusing water, implementing underground water storage, mandating xeriscaping, and treating water as a local product rather than assuming the Water Fairy will always deliver water as needed. Las Vegas already has toilet-to-tap reuse of water. Arizona and California will need to adopt such measures too. California will also need to strictly regulate groundwater pumping. It is the only state that doesn’t do so, which to my mind, is nearly criminal, and leads to such atrocities as water being pumped from desert aquifers to be used in bottled water. (Newly-passed California laws on groundwater pumping will take years to implement and are mostly toothless.)
According to the researchers, the state may weather the changes without experiencing serious economic or social difficulties, assuming it does one big thing:
Start acting more like Arizona where water is concerned.
Researchers at the University of California-Davis Center for Watershed Sciences constructed a computer model of the consequences of seven decades of drought in California. As reported in the Los Angeles Times, their findings were surprisingly upbeat. With some exceptions — notably the disappearance of a substantial amount of Imperial Valley agriculture — the California economy could thrive despite long-term mega-drought.
Australia survived a brutal drought recently by simply learning to use less water. California will no doubt do the same, especially if it becomes clear the previous 150 years were exceptionally wet.
Currently, California gets a huge share of Colorado River water, which discourages conservation. However, there is no way in Hell California would continue to get full allotments if cities in other states started to go dry. That simply would not be allowable politically, the Law of the River be damned.