> We have a federal government to resolve conflicts between the states.
Water law is unfortunately mostly a state issue, and the federal government has been loathe to get involved in mediating water disputes.
> Once ownership is settled, it's pretty clear what rights an owner has over that water vs. a non-owner.
Coming up with a clear allocation of rights ("all water now belongs to Bob") doesn't mean its easy to come up with a good allocation of rights.
> The law being a mess is a common problem with the current government, again not so much about water, water is just becoming one of the many things it sucks at managing.
I didn't say the challenges were unsolvable, I said that the usual political infighting will get in the way of us solving them.
> What percent of the US GDP do you think the government would need in addition to what it already takes in so that over the next couple of decades it can create and maintain desalination and other technology to get rid of the scarcity issues?
That's an entirely theoretical question. We've hit such political gridlock that we can't even maintain the infrastructure we have, much less build new infrastructure.
> I don't see the connection from privatization --> slavery
Controlling a fundamental resource is a great way to enslave people.
> Speculating about what might be the definitive issue that people 50+ years from now look back on these previous and upcoming decades, there are a lot of things that seem more likely to be the issue than "water rights".
50 years really isn't that long (Lisp is 55 years old, UNIX is 43 years old). It's not like we can't even fathom what the world will look like 50 years from now--it won't look all that different from today. Sitting here now, knowing what we know, it's hard to think of any other issue that's going to be as pressing in the next 50 years. Especially considering that some of the other pressing issues (like climate change, alternative energy) are going to put pressures on freshwater resources first. We're not going to run out of oil in 50 years, we're not going to get hit by a meteoroid, etc, etc, but it's very possible that the Ogallala will dry up devastating American food production.