Not much. 0.04% of US water production. For context, that's about 3% of the water consumption of our golf courses, and less than 1% of what we use to water our lawns.

All US data center water usage is less than the total water used for golf courses or the total water used to grow alfalfa. Less water used in evaporative cooling means more electricity is used for cooling given that the efficiency almost doubles if you add evaporative cooling to a chilled water loop.

It’s bad to pump non-renewable fossil aquifer water in Arizona for evaporative cooling, but using cooling towers in an area that gets 30” or more of precipitation per year is probably not going to hurt anything.

The question is does DC building bring added costs to local communities. My small town has a backlog of home builders waiting for permits because of constrained municipal water capacity. We are still paying off the bonds for the last capacity we added. Golf courses/etc are already factored into current costs. Additional new use brings significant cost (bonds to build new capacity), funded by increasing expenses on the entire community, not funded by those who financially benefit from the new build outs.

The issue isn't comparative usage to existing hookups, it's new cost burden on the local community where a data center is built. Which is why DC propogandists switched to the golf course measurement, it confuses the original concern, the cost to the community of new DC hookups to municipal water or the very limited amount (of expensive to the community) available hookups that were intended/funded by the community for other purposes.