First, since data centers likely need some kind of treated (i.e. demineralized) water, and they want to use local municipal supplies, then they can do so only if they pay full market rate for that water. I would push for them to pay 1% to 5% above market rate to help offset other costs, but market rate at minimum. At no point should homeowners and/or residential customers subsidize this usage.
Second, commercial users (including data centers) should only get water produced by treatment plants in excess of residential needs. Plants can only treat so much, pipes can only carry so much, and priority goes to residential first.
Third, ground water is off limits for any commercial/industrial evaporative cooling uses. If data centers want to cool that way, then they need a different source of water.
Did I miss anything?