Adaptive Green Infrastructure Strategies for Stormwater Management in Urban Watersheds Under Changing Climate Scenarios

The increasing impacts of climate change pose significant challenges for urban watersheds, necessitating effective strategies for stormwater management. This study evaluates the impacts of climate change on stormwater runoff and nutrient loads in the Sweetwater Creek Watershed, employing an integrated approach combining climate modeling, hydrological simulations, and green infrastructure (GI) optimization. Utilizing downscaled and bias-corrected data from eight General Circulation Models (GCMs) under two emission scenarios (SSP245 and SSP585), we project future changes in precipitation, temperature, and potential evapotranspiration (PET) for three timeframes: historical (1985–2014), near-future (2020–2049), and far-future (2070–2099). Projections indicate a 15%–25% increase in annual precipitation and a 2°C–4°C rise in average temperature under SSP245, with more extreme changes under SSP585, including up to a 40% increase in precipitation and a 5°C–7°C rise in temperature by the far-future period. These changes are expected to drive a 30%–45% increase in annual runoff volume and a 20%–35% rise in nutrient loads (e.g., nitrogen and phosphorus) under SSP585. The Storm Water Management Model (SWMM) was calibrated (NSE = 0.82) and validated (NSE = 0.79) using historical data to simulate hydrological processes and nutrient transport within the watershed. Using iPlantGreenS², a web-based GI planning tool, optimal GI locations and configurations were identified based on cost-effectiveness and nutrient removal efficiency. GI solutions, such as bioretention cells and vegetative swales, reduced runoff volume by 20%–35% and nutrient loads by 25%–40% in the near-future scenarios, with cost-effectiveness ratios ranging from $50–$150 per kilogram of nutrient removed. However, GI effectiveness declined by 10%–20% under extreme far-future climate conditions, emphasizing the need for adaptive designs to accommodate higher variability in precipitation and temperature. These findings highlight the critical role of GI in enhancing urban water management resilience and provide actionable insights for policymakers and urban planners.