San Antonio gets the majority of its water from a series of submersible pumps in the Edwards Aquifer. Albeit, the wells are only around 500’ deep but it can be done. It is more of a cavernous limestone with infinite permeability. I am not sure what flow capacity the California aquifers have.
Me neither, but IIRC the central valley used to be an inland sea, and I wouldn't be too surprised if there are limestone formations under it.
Still, by reducing the demand (purging illegal immigrants), improving water use efficiency, and damming the damned rivers to conserve and even out the flow, the existing resources would ultimately be cheaper and more effective.
The deep aquifers can always be kept as a future reserve, the techniques to extract will only improve over time.
Pumping water is not unique at...its done all over the place...just not regularly at 3,000 feet depth.
Technically, its very possible - oil depths are sometimes measured in miles.
Its just a cost thing. In my neck of the woods (Kansas), wells are 400-1,000 feet, and the cost is a huge factor at those depths.