Calibration of Phosphorus Export Coefficients for Total Maximum Daily Loads of Massachusetts Lakes

ABSTRACT In an effort to develop Total Maximum Daily Loads of total phosphorus for hundreds of Massachusetts lakes we reanalyzed the land use export coefficients of previously published diagnostic/feasibility studies. Typically, literature values for phosphorus loading per unit area of land use overestimate total phosphorus loading to Massachusetts lakes. We used a stagewise regression technique to screen a variety of models and to select export coefficients that were reasonable, based on the literature, and which offered a good fit to the data. The final model was verified by predicting phosphorus loadings to an independent set of Massachusetts lakes with an average error of 36 percent. The process has been automated with the use of the Arcview Geographic Information System computer system and digital maps of land use. With additional data, the model can also be used to predict lake total phosphorus concentrations under a variety of proposed land use management plans.