Idk how energy-efficiently desalination can be done on a large scale. There are also ways of sterilizing and filtering wastewater, but I think people shy away from that. I think hyperloop will simply be a reality in the coming century and people will live and work hundreds of miles apart. Ultimately, this will be good because it will mean people have to conserve as individuals instead of as local communities, which will be good for the planet as a whole. The downside is that it's not easy to get people to take personal responsibility and the consequences of them failing to do so are harsh.

It will also mean getting around car-free once you leave the hyperloop port, by whatever means that takes place (automatic cars? local transit? bike riding?).