Simulation of Water Quality and Primary Productivity Control Strategies for Lake McCarrons

A one~dimensionallake water quality model, MINLAKE98, was calibrated to simulate water temperature, dissolved oxygen, total phosphorus and chlorophyll~a in Lake McCarrons, a lake with 0.33 km2 surface area and 17.3 m maximum depth located in Roseville, MN. To improve the summer water quality of the lake, several management options have been considered. The potential effects of five of these management options were simulated using the model calibrated for 1995 and 1996 inflow and weather conditions. The model projected that total inflow diversion during the summer, phosphorus treatment of the inflow during the summer and reduction of phosphorus release from the anoxic sediments during the summer have all only a minor effect on phytoplankton standing crops in the lake. Phosphorus removal (precipitation) after ice~out (before the growing season) and artificial deepening of the surface mixed layer to 8 m or more were projected to give a significant (more than 50%) reduction in phytoplankton standing crop.