Water usage of the DC itself can vary a lot. If they're in an area where clean water is cheap, then they might use evaporative cooling which probably has the most significant water consumption (by volume and the fact that it's been processed to be safe to drink). In other areas they may use non-potable water or just a closed loop water system where the water usage is pretty negligible. The electricity is going to be the much larger consideration on the larger scale (though still affected by local grid capacity). Also, the capital cost is a very significant part of these systems: there's a pretty big gap in pricing between 'worth building' and 'worth keeping running'.

(I recommend this video by Hank Green on the subject: https://www.youtube.com/watch?v=H_c6MWk7PQc . Water usage of data centers is a complex and quite localized concern, not something that's going to be a constant across every deployment)