Modeling hypoxia in the central basin of Lake Erie under potential phosphorus load reduction scenarios

A 1-dimensional (vertical), linked hydrodynamic and eutrophication model that was previously calibrated and corroborated with 19 years (1987-2005) of observations in the central basin of Lake Erie, was applied as part of a group of models capable of forecasting ecosystem responses to altered phosphorus loads to Lake Erie. The results were part of the effort guiding the setting of new phosphorus loading targets in accordance with the Great Lakes Water Quality Agreement. Our analysis demonstrated that while reductions in total phosphorus loads can be expected to reduce hypoxia and chlorophyll-a impairments on average, climate and meteorological variability will result in significant year to year variability. We provide examples for achieving hypothetical water quality goals and relate the required reductions to recent nutrient sources.