Lake Assessment Program - Grindstone Lake, Pine County

Grindstone Lake is located in Pine County. It is a large size lake (533 acres). Land use in the watershed is characterized by water and marsh (48 percent) and forest uses (27 percent). This land use composition is fairly typical for lakes in this region of the state - Northern Lakes and Forests ecoregion. Grindstone Lake was sampled during the summer of 1993 by the Minnesota Pollution Control Agency (MPCA) staff and citizens from the Grindstone Lakeshore Property Owners' Association (Association). Water quality data collected during the study reveal a summer mean total phosphorus concentration of 16 ?g/L, mean chlorophyll a of 6 ?g/L and Secchi transparency of 10.2 feet. These values are within the range of values exhibited by reference lakes in this ecoregion. Total phosphorus, chlorophyll a and Secchi transparency help to characterize the trophic status of a lake. For-Grindstone Lake these measures indicate mesotrophic conditions.