We are working on the El Yunque National Forest Visitor's Center Renovation.  El Yunque is the only U.S. national park that is in a tropical rainforest. This U.S. Forest Service facility was severely damaged in 2017 during Hurricane Maria.  Our question has to do with the Visitor's Center water supply.  

Because the facility is located in a rainforest - with an average annual rainfall of 120 inches - the USFS built a water collection and treatment system to provide water exclusively to the Visitor's Center and adjacent administrative building.  Water is collected in a 4" gravity fed pipe from a small rainwater fed pool around 1/2 mile up-slope from the facility to a sediment filtration and treatment facility around midway, where it is stored in a 30,000 gallon cistern tank.  From there, the water is fed to the project.  The system is 100% gravity fed, and uses no electricity, and maintains around 50 psi.

So our question is - can the off-site rainwater harvesting system described above count as an alternative water source for Indoor Water Use Reduction, as it is a dedicated system that serves only the Visitor's Center facility and administrative buildings?