Considerations of cost efficiency and the sustainability of the backup supply system lead to the concept of “right-sizing” of the building-scale rainwater harvesting system. This is the combination of roofprint and cistern volume relative to the expected water usage profile that would result in only limited backup supply requirements, needed only during the worst drought periods.
roofprint commensurate with water demand. Then too storage cisterns would take up space, unless they were integrated into the building envelope. All that would have implications for development style, and so would require some tinkering with prevailing development models.