The role of rainwater harvesting in urban stormwater runoff in the semiarid region of Brazil

Rainwater Harvesting System (RWHS) can play a multipurpose role, contributing to the management of rainwater runoff, in addition to the water supply. This article assessed the potential reduction in stormwater runoff by adopting small-scale RWHS in the Brazilian semiarid region based on the Curve-Number (CN). RWHS could minimize runoff in frequency and volume, leading the built environment to perform closer to the land’s natural conditions. Before urbanization, the region had a CN of 76. In post urbanization, a case study of multiple houses showed that the adoption of RWHS could reduce the CN from 86 to 80. A reasonable design (0.5 demand fraction and 2000 L tank capacity) could minimize runoff volume by 34% and frequency of occurrence by 66%. Even RWHS with a minimal design, i.e. small tank capacity and low demand, might contribute to the safety of people, resilience, and sustainability of the city’s infrastructure.