AbstractThis research demonstrates that modeling approaches can be used to identify priority areas to implement green stormwater infrastructure (GSI) resulting in improved water quality outcomes. The total suspended solids (TSS) washoff loading from watersheds in Lucas County, Ohio due the municipal separate storm sewer system (MS4) was reported based on 2015 rain data. The highest TSS loading was experienced in the winter season in 80% of the watersheds. Subcatchments with the highest predicted TSS washoff loadings were identified as priority areas or hotspots. In subsequent simulations, GSI implementation in hotspots improved water quality by more than twofold as compared to indiscriminate implementation of GSI. These hotspot maps are being used by regional stormwater stakeholders to focus their urban water quality efforts and to identify site characteristics that may be used to inform environmental policy.