Simple Modeling of Rainwater Capture and Reuse Potential: Maximizing the Environmental and Economic Benefits to Public and Private Entities

Legislation is being advanced to Cincinnati’s City Council that will allow rainwater harvesting and reuse for non-potable applications. This has significant implications for the local wastewater utility that charges users based on metered potable water purchases. The need to ensure accurate sewer billing, combined with a need to remove stormwater from the combined sewer system instigated an investigation of the potential combined sewer overflow reductions the utility could realize if rainwater harvesting was implemented. The result of that investigation is an Excel-based model that can calculate the peak flow reduction that the sewer system could experience from a building with any combination of cistern size and daily non-potable water usage. The tool can also be used by building owners to determine what fraction of their non-potable water usage can be collected with a cistern. These functions allow the model to maximize the public and private environmental and economic benefits.