>...the amount of water we’re talking about isn’t much on a national scale.

Water issues are always local issues. There is no national water distribution system or national aquifer.

>this will mean companies making some positive change in the communities where they build datacenters.

This will remain to be seen. So far, if it had worked out that way then there would be less vocal opposition to these data centers. Local perception seems to be that there will be nuisance to dangerous noise levels; heat islands which can cause local disruptions to weather events; closed-door agreements to build this infrastructure instead of open community involvement in the process; and other issues including concerns about excessive water usage especially in areas where there are already troubling water availability trends due to other forms of development.

>when more natural gas and coal plants are coming online.

Here in NTexas, the availability of and proximity to natural gas compression stations is key to data center siting from the ones that I have monitored. Plans seem to include construction of gas turbine generators to power the new data centers and these generators are sited on parcels very close to existing compressor stations and high-voltage power lines and small or medium local lakes.