fossil water is not an issue - aquifers are constantly replenished with rainwater (and manual recharging via pumping treated water back into the aquifer...a debatable idea). At least that's the case in the mid- and north-west. Coastal and dryish states may vary. I seem to remember seeing somewhere that Los Angeles was putting an evaporative water purification plant in, which would give the aquifers in that area a rest.

fossil fuel, however, is still an issue.