Lake Assessment Program - Trout Lake, Itasca County

Trout Lake is located in northern central Minnesota. With a surface area of about 1900 acres and a maximum depth of 135 feet, it is among the upper ten percent of lakes in the State in terms of size and depth. The water quality, ecology and basin morphometry of the lake have been impacted by human disturbances in the lake's watershed. Included among these impacts was the discharge of fine ore tailings into the lake from about 1907-1940 and the discharge of wastewater from the Cities of Coleraine and Bovey. The wastewater discharge was diverted from the lake in September of 1987. Trout Lake was sampled during the summer of 1987 by the MPCA and citizens from the Coleraine-Bovey area as a part of the Lake Assessment Program. Water quality data collected during this effort revealed relatively high average total phosphorus concentrations (44 ug/1). Compared to other lakes in this region, this concentration would rank at about the 15th percentile, which means that about 85 percent of the lakes in this region exhibit lower total phosphorus concentrations. This elevated level of total phosphorus was accompanied by relatively high chlorophyll-a concentrations with a mean concentration of 14 ug/1 and a maximum concentration of 34 mg/1. Algal blooms were common during the summer of 1987 and tended to be characterized by large colonial blue-green forms. Secchi transparency was high (mean= 12 feet) relative to the total phosphorus and chlorophyll-a concentrations.