California has plenty of water for it's people. If you add up ALL residential, commercial and industrial use, including all outdoor landscape watering, baseball fields, golf courses, etc - it all adds up to around 10-20% of the water used (depending on rainfall).
Where does the rest (80-90%) of California's water go? Agriculture. Half the produce of which is exported to other states and countries. Did you know CA grows a LOT of rice near it's capitol, which is naturally almost a desert? And about half of that rice is exported, much to Asia (!!)
California is rather like Saudi Arabia, with the farmers pumping out all the water and selling it in the form of agricultural produce.
But take a shorter shower please! And you don't really NEED to flush that toilet.