Modeling Suburban Phosphorus Runoff and BMPs: Downscaling from Watershed Systems to Site-Specific Scales

Modeling nutrient pollution remains important in assessing and managing impacts on aquatic ecosystems. Phosphorus is a limiting factor in inland water bodies, and there is a need for modeling land use impacts on loading at multiple scales. Downscaling watershed simulations to practice at site scales remains a difficult challenge. A combination of simulation, statistical, and spatial models is used to study phosphorus pollution in the Charles River Watershed in Massachusetts. The study downscales watershed-wide results to site-specific and neighborhood scales. Stormwater best management practices (BMPs) are modeled for removal effectiveness based on hot spots of phosphorus loading and flow accumulation patterns. It is observed that phosphorus loading is influenced by multiple variables and with spatial influence. Infiltration trenches, bioretention areas, and dry swales are found to be effective if placed in strategic locations and with consideration of scale of flow accumulation. Watershed managers and land use planners could translate watershed ecosystem dynamics into site and neighborhood design decisions. Recognizing land-cover types that contribute to pollutant loading and prioritizing BMP implementation according to hotspots allows for both economic efficiency in pollutant removal and BMP implementation. (C) 2017 American Society of Civil Engineers.