Big Fork River Watershed Monitoring and Assessment Report

The Big Fork River Watershed is located in northern Minnesota, split between Itasca and Koochiching counties. The watershed drains over 1.3 million acres and contains many lakes, wetlands, and forests. Agricultural and urban land uses are not common; rather forestry and tourism are the dominant industries within the watershed. The major river in the watershed, the Big Fork River, starts at Dora Lake and winds its way north before flowing into the Rainy River. The river is an outstanding recreational resource offering fishing and canoeing opportunities for people seeking a northern Minnesota wilderness experience. The Minnesota Pollution Control Agency (MPCA) began an Intensive Watershed Monitoring (IWM) program within the Big Fork River Watershed in 2010. The monitoring was comprehensive and included the collection of samples from lakes, streams and groundwater. Biological data was collected from rivers and streams to assess aquatic life and aquatic consumption. Water chemistry information was collected to assess surface waters for aquatic life and aquatic recreation as well as computing pollutant loads through the Major Watershed Load Monitoring Program (MWLMP). The work was carried out by staff from the MPCA as well as citizen volunteers. The results of this monitoring effort were used to assess the Big Fork River Watershed in 2012. The assessment results for the Big Fork River Watershed indicate that the condition of the lakes and streams are good to very good, even though there were a few impairments found. The most widespread impairment found in both lakes and rivers is due to high mercury levels limiting the aquatic consumption of fish. The remaining impairments throughout the watershed consisted of low dissolved oxygen (DO), fish and macroinvertebrate, and nutrient impairments. Many of the aquatic life impairments were found to be the result of natural conditions within the Big Fork River Watershed.