W = external P load + internal P load

W is the annual P load (kg/yr)
Calculating the budget
The phosphorus budget is a way of mathematically calculating the nutrients coming into and leaving the lake over the course of a year.
It is :
�Based on other scientific studies on freshwater lakes

�The model uses coefficients and the area of different land uses to estimate the P contribution of the watershed to the lake

�The percent contribution is a reflection of the coefficient, which is determined by the degree to which that source contributes phosphorus to the lake.  The contribution of the different land use types is also influenced by the land area of the watershed and the area of each land use type within the watershed.

�The model was adjusted to agree with empirical data we collected and the unique character of Togus Pond and its watershed.