A framework for creating sustainable rainwater harvesting and reuse strategies for urban landscape irrigation in a changing climate.

Rainwater harvesting and reuse with rain barrels/cisterns holds substantial potentials to restore urban hydrology, improve water quality, and provide a resource for landscape irrigation under current and future climates. However, to assist decision-making, a systematic framework needs to be created to develop sustainable rainwater harvesting and reuse strategies for urban landscape irrigation considering their multi-functional impacts in a changing climate. This study created a novel framework for developing sustainable rainwater harvesting and reuse strategies for urban landscape irrigation in a changing climate with various components, including changes in climate parameters, baselines with/without rainwater harvesting/reuse, potential scenarios with rainwater harvesting/reuse, and identification of sustainable strategies using individual and combined indicators (discharge volume, peak discharge, combined sewer overflow-CSO, freshwater demand, and plant growth). The framework was demonstrated using the Soil and Water Assessment Tool with closed pipe drainage network (SWAT-CPDN) in the Brentwood watershed (Austin, Texas). Compared to the baselines (without rain barrels/cisterns), rainwater harvesting/reuse strategies with the most benefits under historical climate (2000-2014) and future climates (2080-2099 under two Shared Socioeconomic Pathways-SSP2-4.5 and SSP5-8.5) reduced discharge volume by 8.51 %-8.75 %, peak discharge by 4.83 %-5.28 %, CSO by 5.24 %-5.56 %, and freshwater demand by 22.91 %-24.93 %, while maintaining plant biomass. The most sustainable rainwater harvesting/reuse strategy needs to be obtained by evaluating their impacts on combined indicators with well-defined weighting factors and minimum/maximum criteria for individual indicators under each climate condition. The framework created in this study can guide decision-making for sustainable water management in future urban planning initiatives.