The problem is where you going to store after you use it to regain energy? You can't simply dump it back into the wild, freshwater is simply too precious in California for that.It’s funny because Lake Arrowhead in CA would be great. Only a few miles the elevation drops ~3000 feet.
The lake has 15,640,000,000 gallons of water. 3000 ft of head is 1300PSI.
550 watts per GPM. Could get a couple of gigawatts out of it.