A vertically-segmented, dynamic phosphorus model program was developed for use on a 16 bit microcomputer. The predictive model includes theoretical equations for physical settling, thermocline diffusion, and sediment release of total phosphorus. The model was developed and calibrated using actual data collected from 1980 through 1982. Input loads from combined point and nonpoint sources were entered using a time step equal to 1 day. In the case of Lake Wallen-paupack, discharge occurs from both the epilimnion and hypolimnion during the latter portion of the stratified period. Several discharge scenarios were evaluated to determine if any one would produce a significant reduction in summer epilimnetic phosphorus concentrations.