It is likely that the amounts of water used by data centers is considered - legally - proprietary. The backers, developers and operators will likely retain that privilege unless required by law to divulge the information. A suggestion to politicians might help.
https://www.npr.org/2026/04/20/g-s1-117729/data-center-disputes-local-midterms
A wee shame that our political system does not utilize referendums, e.g., does the majority of the public want and/or need A.I.? Does it want and/or need self-driving vehicles? A truly democratic society would put these issue to the public instead of confining them to usually-compromised politicians.