That's part of it. A lot of people live here because it's a great place to live, and they're water hogs. People in urban environments can be bullied to huge degrees to conserve water. So yes, California has a big demand for water there, but it also has a big demand for water in its agriculture. The Valley -- the San Joaquin Valley, once a big inland sea, is hugely fertile and plopped in an ideal climate. It has fed and clothed much of the U.S. It needs water to do that. Necessarily that means sacrificing some pretty things, but the payoff is that the things not sacrificed can thrive, including other natural areas.
How much water isn't agriculture getting because government says it is environmentally immoral to sacrifice lakes, or some obscure species of fresh water fish, or even beautiful canyons for reservoirs? Is there really a shortage of water, or is it an overabundance of environmental tyranny?
When Americans were free to fish the oceans on a minimum standard of regulation, seafood was plentiful and cheap, and sea lions, elephant seals, seals, etc., (piniped type critters) were plentiful. Those animals eat a lot of fish and steal fish off fishermen's lines -- a $50 bill to the guy fishing to feed America. Those animals are also smart, and will avoid things they know are dangerous. So when fishermen shot at and killed them, it kept the population within sustainability. But to "protect" these poor animals, regulations prevented fishermen from managing their resource. More pinipeds bred, ate fish freely. Their populations exploded and had a huge impact on the fish populations.
Then MORE government stepped in to "manage" fishermen into not overfishing the resource, blaming them for what the pinipeds were doing. Now "protected" seals and sea lions are so overpopulated that they are literally sinking sailboats in "protected" harbors.
There are lots of fish in the Pacific. Fish is expensive and hard to get because of environmental government tyranny. The fish is plentiful. It's an expensive luxury because commerce-killing environmental tyrannically regulation that makes outlaws of Americans who would fish and have fished America's coasts in smart, self-preserving way. We don't need no vapid bland tilapia! Salmon and tuna are plentiful. Government tyranny is the reason it is rare and expensive.
I have a hunch it's the same with starving one of the most fertile and productive food producing regions in the world. The water's there, even now, though plenty thin (my mom has lived in California for 85 years, and says she can't remember it ever being this dry this long). It's not a change in resources that we need, it's a change in priorities.
“It’s not a change in resources that we need, it’s a change in priorities.”
I did not live as long as your mom has in California, but I did spend most of my childhood there, and finished highschool and college there. I have also looked at a lot of California’s history, including its natural history.
The soil in the San Joaquin basis is fertile, and as you say it was once (for a time) a large inland sea - when it was wet everywhere that fed into the rivers in the area. The long truth is that the long general history has been floods and droughts. Some droughts in the last 8,000 years have lasted - altogether, from earlier hihgs - 200 years.
I undestand and agree that the regulatory conditions that are favoring “the environment” are unnecessary in their extreme, and should be moderated and modified.
My only serious point is that it is my belief that even doing 100% of that will not solve the totallity of water supply versus demand issues in California.
That even accounting for moderated demands for environmental needs, that the “natural” (long historical water supplies) never had, and may never have had and may still never have the “natural” supplies to fulfill the demands of “moderated” environmental needs + population + industry + agriculture in a way that long term natural supplies can provide, against the ambitions of everyone that wants some of it.
My belief is that if California wants to keep and eventually (growth???) exceed the demands already being asked of its natural water supply ability, it can help by doing lots of good and needed changes (corrected many errors as you suggest) but it cannot fully succeed without building desalination plants.