I don't think your comparison was unfair. It's impressive that LV has managed to manage\recycle their water as much as they have but to me it is shocking that they still somehow consume 5-6 times as much per capita as Oslo (and, according to some basic searching, much of the EU). Not wanting to turn this into the usual EU\US back-and-forth, but ... man how is it possible to use that much water?
If you're dividing the whole county's water consumption by the county's population to get a usage-per-capita figure, that's going to be incredibly distorted by the Las Vegas strip (hotels [luxury showers and toilets that actually flush], pools, fountains, etc) and related (golf courses). These don't contribute to the denominator, but contribute enormously to the consumption. (If golf and the hotels consume 14% together, that would increase the per-capita consumption by 16%.)
I guess it'd depend on how this is counted. If it is simply "total volume of gallons of water consumed divided by permanently resident population" then your suggestion probably explains the bulk of it. I would have hoped that it'd be measured slightly smarter however.
