It may be possible to work ...

It may be possible to work with the local water utility and establish the campus area as a district metered area.  This will allow you to monitor the rate of flow into the campus area during day and night as well as total feed to the zone.  Presuming that there is no significant tank storage and meters are in place at individual buildings, a comparison of the aggregate meters and the district meters will provide an answer.  If the campus water is not metered by an aggregate of buildings, district metering can still help to estimate leakage but looking at minimum flows.