That's only if we build massive dammed reservoirs that try to serve dense populations from a single source like Hetch Hetchy supplying the Bay Area. A system of smaller reservoirs dotted across the state would serve the same function without the concentrated ecological impact. San Francisco has three terminal reservoirs within its city limits, for example.

> The big one is water rights. The water is not the states to impound in the first place in many cases. If I have particular water rights, and you block them, I can sue you out of existence under existing laws, laws that are going to be very hard to break with our current legal system.

That's why utilizing the whole water cycle is important, rather than concentrated sources like rivers and streams. A farmer can prove you're taking his inch of water by comparing upstream of the installation but it's much harder to do that if snowmelt is being collected in hundreds of smaller reservoirs along the mountains. (IANAL, so grain of salt and all that)