Building Level Water Metering

I have a doubt, we have a project of a complex of 3 buildings that is located inside a University Campus. In this Campus there are 2 global water meters with their respective monthly receipts that leverage the total consumption of the campus. I understand that the WEp2 asks me to measure the total potable water use for the building and associated grounds. But I do not have a meter and / or a monthly receipt that records the exact water consumption for that complex of 3 buildings. On the other hand to comply with the WEc4 water sub-meters have been installed to record the water used for indoor plumbing fixtures and fittings (In each of the 3 buildings) and 2 sub-meters for irrigation for the green areas surrounding the project. Being the only uses for the water: Indoor plumbing fixtures and fittings and irrigation). It is possible that the data recorded by these sub-meters can help me to comply with the WEp2, If these together sum total of the consumption of water (indoor plumbing fixtures and fitting plus irrigation) for the 3 buildings? I hope you can help me to solve this doubt, Regards