An integrated framework for stormwater management and life cycle assessment of rainwater harvesting: A comparative...

Green infrastructure, which is designed to provide sustainable and resilient stormwater management solutions, inherently supports flood mitigation, pollution reduction, and a decentralized water supply. When proposing this type of infrastructure, it is important to identify environmental trade-offs related to their implementation. Our research focuses on a city-wide rain barrel (RB) deployment in northern and southern California, San Leandro and Imperial Beach, respectively. San Leandro and Imperial Beach are similar in that they are both low-lying coastal areas, containing a high percentage of residential areas with several census tracts listed as disadvantaged. A key difference is that San Leandro receives approximately 2.5 times the annual rainfall as Imperial Beach. This work utilizes PCSWMM for stormwater modeling to quantify captured stormwater, changes in conventional stormwater management (such as ocean outfall stormwater pumping), and reduced pollutant loading for RB deployment. Stormwater modeling is combined with Life Cycle Assessments (LCA) to quantify trade-offs in terms of Global Warming Potential (GWP), Human Toxicity Potential (HTP), Ecotoxicity Potential (EcoP) and Eutrophication Potential (EP). In Imperial Beach, RBs reduce GWP by 2.6 × 10⁶ kg Carbon Dioxide Equivalent (CO₂-Eq) and increase HTP by 3.8 × 10⁶ kg Dichlorobenzene Equivalent (DCB-Eq). In San Leandro, GWP reduces by 1.3 × 10⁷ kg CO₂-Eq, and HTP increases by 4.7 × 10⁶ kg DCB-Eq. In Imperial Beach, a reduction in runoff from captured rainfall results in a 44 % reduction of pollutant loading, while San Leandro sees a 27 % reduction. These reductions are equal to the reductions in EcoP and EP. Normalized per 1 m³ of collected stormwater, there is a lower reduction in GWP for Imperial Beach than San Leandro, and a higher contribution to HTP. This study advances current knowledge by quantifying RB benefits through multiple sustainability metrics, while comparing two underserved coastal California communities with distinct rainfall patterns. It demonstrates that while RBs reduce runoff and pollution, they also present environmental trade-offs, providing key insights for green infrastructure deployment.