Rainwater harvesting with rain barrels and cisterns for sustainable urban stormwater management

Abstract:

Low impact development (LID) practices are effective in restoring hydrological processes in urban areas. The efficiencies of implementation strategies differ for various spatial locations, types, and implementation quantities of LID practices. Therefore, being able to simulate the effectiveness of LID practices accurately is very important in managing urban watersheds. In addition, rain barrels and cisterns, a popular type of LID practice, can harvest roof runoff. The collected rainwater can be used for irrigation during dry days to reduce water usage. In this study, the Soil and Water Assessment Tool (SWAT) was improved and used to assess the effectiveness of rainwater harvesting with rain barrels and cisterns in the Brentwood watershed, an urbanized watershed located in Austin, TX. The first improvement was the equation used to calculate the amount of water percolating into the soil. Second, the bypass from the rain barrels and cisterns was considered as rainfall evenly distributed over the non-roof areas. Third, the soil profiles were modified to be updated sub-daily to reflect the sub-daily time steps of rainfall and irrigation input data. Fourth, the pervious and impervious areas were separated to calculate infiltration. Fifth, reusing the rainwater harvested for auto landscape irrigation was improved. Sixth, lawn management operation was enhanced. After the model improvements, the impacts of rainwater harvesting with rain barrels and cisterns on sustainable urban stormwater management were evaluated with various implementation areas and sizes of rain barrels and cisterns, and different rainwater reuse operations for landscape irrigation. The improved SWAT model is helpful for stakeholders to make effective implementation and operation plans for rainwater harvesting with rain barrels and cisterns to achieve sustainable urban stormwater management.