The application of an analytical probabilistic model for estimating the rainfall–runoff reductions achieved using a rainwater harvesting system Original Research Article

Rainwater harvesting systems cannot only supplement on-site water needs, but also reduce water runoff and lessen downstream flooding. In this study, an existing analytic model for estimating the runoff in urban areas is modified to provide a more economical and effective model that can be used for describing rainwater harvesting. This model calculates the rainfall–runoff reduction by taking into account the catchment, storage tank, and infiltration facility of a water harvesting system; this calculation is based on the water balance equation, and the cumulative distribution, probability density, and average rainfall–runoff functions. This model was applied to a water harvesting system at the Seoul National University in order to verify its practicality. The derived model was useful for evaluating runoff reduction and for designing the storage tank capacity.