That's because it's a large industry and nobody lives there. This pattern appears all over the place. The paper mills in the pacific northwest consume large multiples of the water used by their little towns.
Assuming that the population is the same in the city and you just move residents into an apartment complex. I don't understand how you would get the same water consumption, am I missing something? Evaporative cooling is extremely water heavy and these facilities also have the normal HVAC you'd expect. Everything just seems to point to more water usage not less.
Under reasonable assumptions, the apartments would use more water.
- Google's datacenter complex in the Dalles covers ~190 acres.
- Typical density for apartment buildings is 50 units/acre, meaning you'd have 9,500 units on 190 acres.
- Average household size in the US is 2.5, so the 9,500 units would have a population of 23,750.
- According to the original article, per capita domestic water usage in the U.S. is 82 gallons per day, meaning a total water consumption of 710M gal/yr for the apartments. And this doesn't count the substantial indirect water usage you'd need to support this population.
- The Google datacenter uses 355M gal/yr (per the Oregonian article).
- 710M > 355M
Now, it would be somewhat ridiculous to replace the entire Google datacenter with apartment buildings in a rural town with declining population, but that was the original question...