Water quality of four lakes in Lakeville, Minnesota

Water-quality characteristics were determined for four selected lakes to provide background data for evaluating changes that may occur in the lakes because of urbanization. Precipitation of calcium carbonate is suggested by high pH values and a decrease in the calcium concentration when magnesium, sodium, and chloride concentrations increase. Pollution is indicated by chloride concentrations that increased from 18 to 57 milligrams per liter in 1978. The eutrophic state of the lakes is suggested by dissolved oxygen supersaturated near the surface and less than 0.1 milligram per liter near the deepest parts of the lakes. Determination of the trophic state of the lakes provided trophic state indices as high as 69-2. Phosphorus concentrations were significantly higher in two of the lakes sampled. Anacystic and Oscillatoria were the dominant phytoplankton genera. Phytoplankton blooms occurred throughout the year with the highest sampled concentration yielding 890,000 cells per milliliter.