The bulk of California’s water comes from Sierras snowpack. This year, the snowpack numbers are dreadful. The worst ever previous snowpack was 25% of normal in 1997. This season, which ends April 1, it is a mind-numbing 8%. However, this does not yet herald  The End Of The World As California Knows It. Read on!
Snowmelt from the Sierras flows down to the Sacramento Delta, and then southward via aqueducts to the Central Valley and southern California. In a good rain year, there are too many interests competing for too little water in the Sacramento Delta. This year there will be much less water than normal.
The Colorado River basin had a good year, 90% of normal. However Imperial Valley CA agriculture and southern California lay a big claim to that water, as least 20%, much of which goes for agriculture in a baking desert. They use Lake Mead water for that, as does Las Vegas, Phoenix, and Tucson. If the California drought continues, the big cities of the southwest will almost certainly act to prevent the Imperial Valley from taking its 20% share of all Colorado River water.
However, it may not need to get that. Some wise and calming words from California Water Blog.
Statistically, last year’s drought is about a one in 15-30 year event. With a changing climate and growing water demands, we should prepare for such droughts occurring more than once a generation.
California will not run out of water this year, or next, if we are careful. We will respond mostly as we did last year, with some modest changes.
In rough order of importance, California will make up most of this year’s water shortage by:
- Additional groundwater withdrawals of perhaps 5 million or more acre-feet
- Reductions in urban and environmental water uses and agricultural fallowing — totaling perhaps 4 million acre-feet
- Shifting perhaps 1 millon acre-feet of water use from lower to higher economic values through water markets
- Depleting reservoir storage by perhaps 1-2 million acre-feet
- Increasing wastewater reuse and other conservation efforts
Another problem for California is less water means less hydropower, which results in  reduced supplies of electricity.