Just to emphasize this: the southern San Joaquin valley drains to the ocean only during extreme El Niño events. So basically there is no water left to be captur

Just to emphasize this: the southern San Joaquin valley drains to the ocean only during extreme El Niño events. So basically there is no water left to be captured there. The only water left is north of Sacramento, and is needed to keep the SF Bay alive. Sure, the Bay could survive if a little more water was taken, but that wouldn't be enough to solve the problem.