10 years? Says who? I’ve heard 2 years in a worst case.

With respect. It's a dumb internet-ism not grounded in reality.

https://oroville.lakesonline.com/Level/

You can see the water level there for Lake Orville which is the source for the California aqueduct system that feeds part of the Central Valley and the 20 million living in Southern California. Given that non-residential accounts for 92% of all the water use California is never in any danger of not being able to provide water to residential. That would require 20 years without rain and that also assumes we don't build new reservoirs.

California is the size of a country. The North is in an area more like the Pacific Northwest than any desert.

We just lived through a worst case scenario that lasted 3 years and only on the 3rd year of that did we even bother to start water restrictions. For the past two years we've been full to 100% and having to let it go in the spring.

I did a ton of research on this cause I own a property supplied by this system.