We need to rid ourselves of the mythical notion of "abundant", meaning arbitrarily cheap, energy. There are only a few more doublings of global energy usage left before we heat the atmosphere significantly, not due to greenhouse gases, but by raising the equilibrium temperature of Earth as a radiating blackbody in space.
TANSTAAFL. Every resource is ultimately finite. Let's live within our limits rather than justifying our actions with unrealistic fantasizing about future technology.
Abundant clean renewable energy would solve "rare" water issues.