Modeling phosphorous loads to the Great Lakes under future land use and climatic conditions

http://www.jsonline.com/news/commission-slash-phosphorus-flowing-into-lake-erie-b99362882z1-277765141.html

Phosphorous (P) loads are responsible for increases in algal bloom in the Great Lakes over the last decade. We assess the vulnerability of watersheds in the basin towards contributing P loads in the context of changes in land use and climate. We use statistical and deterministic modeling approaches.

First, plausible scenarios for expansion of urban and agricultural areas over a 30-year period are generated. Land uses are converted to P source terms, which are input to a calibrated model of P fate and transport. Predictions of P loads emanating from the watersheds to the Great Lakes are generated. Watersheds are assessed according to their capacity to attenuate P sources, which is related to land surface properties and hydraulic residence times.

Seasonally-varying, nonlinear regressions between P loads and discharges are fitted to observations. Climate forcings for near- and far-future periods are input to watershed-scale hydrologic models to predict changes in discharges and corresponding P loads. The vulnerability of watersheds to seasonal changes and corresponding P loads varies significantly across the basin.