Various entities in CA have spent a lot of money to prevent flooding, and in doing so they have made very effective systems that shunt freshwater right into the

Various entities in CA have spent a lot of money to prevent flooding, and in doing so they have made very effective systems that shunt freshwater right into the ocean. Because the water is very efficiently moved from streets to drains to cement rivers to whatever it doesn't get a chance to sink in, and that means that a lot of water is "wasted". CA might be in a drought, but it still does get rainfall. Drought != no rain at all, it means less rain than usual. If you don't get much rain, you have to do everything you can to prevent runoff. There's not much of that in CA and so there are problems. It's partially a drought, and partially bad water management that have caused the problems.