Maybe they do commercial customers different, but I’m about 30 miles north of the site in question, and my water use is reported in real time. I can even get a daily report from their web site. It’s hard to believe they’d be less interested in the usage of their 1e6-gallon-per-year commercial customers than their 1e4-gallon-per-year residential customers.

Water company can measure the water that leaves their pumping station(s) - just put a flow meter on the one big pipe. If that doesn’t match the sum of all their customer meters, then water is going somewhere else - broken pipe, illegal connection, meter fraud, whatever.

I would guess that most jurisdictions already have that one big flow meter, because they have to comply with water rights agreements, have to know how much chlorine & fluoride to inject, etc.

Kind of fascinating that they don’t do any kind of reconciliation of water delivered against water billed. You’d think that would be an easy thing to do and a good way to discover leaks (or theft). I mean, there would definitely be ‘missing’ water due to leaks, fire department, etc, but one imagines that would have some kind of normal/tolerable range, and that 30 million missing gallons would trigger some kind of investigation prior to customer complaints.