We are funded by Ohio Sea Grant to estimate the contribution of urban runoff to harmful algal bloom (HAB) formation in Lucas County, Ohio. In August of 2014, there was a disruption in the provision of clean and safe drinking water due to the formation of an HAB in the Western Basin of Lake Erie. Regional stakeholders are interested in determining where to focus their efforts to prevent future HABs.
The quantitative contribution of urban runoff is assumed to be low, but there are no estimates of annual or seasonal loads of contaminants known to contribute to HAB formation (e.g., suspended solids, nutrients). Land use and imperviousness are important factors that contribute to contaminant loads in urban runoff. Human impact on the water cycle is significant due to development and change of land surface from pervious to impervious.
We are using PCSWMM (through a generous grant from Computational We Hydraulics International) to model stormwater runoff quantity and quality. PCSWMM utilizes EPA’s SWMM5 rainfall runoff model which simulates runoff quantity using two components: runoff across the surface of the land and routing through existing hydraulic infrastructure. Site data is input into PCSWMM in layers (shape files) or through GIS files that include site characteristics, elevations, pipe diameters, and catch basin dimensions. In this project, we have been able to quantify contaminant loads and to identify “hotspot watersheds” in Lucas County where we can focus our efforts toward reducing urban runoff.