“It seems there are a lot of legalities involved as to who owns what and who has rights to what.
But I suspect a state can’t wholly own a river which defines part of it’s border but is not within the state’s borders.”
When Boulder Dam was built there was a collateral Federal Water Compact, that apportioned the water (and the electricity generated) behind the dam between AZ and CA. Interestingly, Las Vegas didn’t get any water from Lake Mead, although I think it does now. Until recent years, AZ didn’t take all the water to which it was entitled, so SoCal took it. Now though, as AZ has developed agriculturally and has grown in population, it has started taking it’s full allotment, which has reduced the water going into SoCal at a time when they have already lost an environmental lawsuit which has cut their ability to take water from the Owens River (which runs out of Mono Lake, and the Eastern Sierra watershed). So they are having to rely on water from the Western Sierras and the northern dams like Oroville and Shasta, which also serve Northern California and our Centra Valley ag business. Furthermore, thanks to Jerry Brown, the RATs, and their envirowacko buddies, despite the fact that our population has doubled, we’ve not built a single major water storage facility since 1979. There’s a lot more to the story, but those are the basics.
I expect the Fed government also has it’s finger in the pie somewhere in the mix.