Lake Assessment Program - Long Lake, Hubbard County

Long Lake is a large (1,863 acres) and very deep (135 feet maximum depth) lake located in southwestern Hubbard County. Land use in the watershed is characterized by cultivated (38 percent of the area) and forested (37 percent) land use. The proportion of agricultural land is high for lakes in this region of the state - the Northern Lakes and Forests (NLF) ecoregion (Figure 1). Typically, forested and marsh land uses comprise on the order of 70-90 percent of the land uses within lake watersheds in the NLF ecoregion. Long Lake was sampled during the summer of 1995 by Minnesota Pollution Control Agency (MPCA) staff and citizens from the Long Lake Association (Association). Water quality data collected during the study reveal summer-mean phosphorus concentration of 12ug/L, chlorophyll-a of 3.4 ug/L and Secchi transparency of 13.5 feet. The chlorophyll-a and Secchi values are well within the range of values exhibited by reference lakes in this ecoregion. The phosphorus value, however, is better than the typical range of values exhibited by reference lakes in the NLF ecoregion. Total phosphorus, chlorophyll-a and Secchi transparency help to characterize the trophic status of a lake. For Long Lake, these measures indicate mesotrophic conditions.