Read my link, in San Bernardino a reservoir was built to trap mountain/storm runoff just to replenish the local aquifer instead of losing it to the ocean.
Of course on the other hand here in San Diego, concrete plants aren’t allowed to use sand from the river banks because environmentalists want the sand to wash down stream to the sea but it’s okay to import sand by train from Baja. Go figure.
Then I think in Long Beach there is a water reclamation plant (from sewage) where citizens refuse to drink reclaimed water so it is pump into the local aquifer, re-contaminated then pumped back out for use by the water department. Same with a desalination pilot plant up, the pure reclaimed water is pumped into the ground.