That link (https://cdec.water.ca.gov/resapp/RescondMain) just times out for me, might be yet another American site that just geoblocks all European IP addresses. Here's an archive copy for those who need it: https://archive.is/oZodo

Hmm... even though they're all above historical averages right now, it looks like they're only about 79% full (mean of the capacities in the graphic). Unless they get sustained high precipitation over several years, the reservoirs might not reach capacity.

If they build more reservoirs but the rains don't keep up, a lot of it would still be lost to evaporation.