Historical Lake Vermilion Water Quality Data

Secchi Disk Data

Historical Secchi transparency data, which date back to 1976, reveal a significant improvement in transparency based on 26 summers of data. During this 32-year period, the summer mean Secchi has improved from near 5 feet in the late 1970s to 8 feet in the late 1990’s. Mean values after 2000 have improved further to the 9-foot range.

The MPCA has compiled this historical Secchi data in an easy-to-read format here. While the data are from a single site in Big Bay near Pine Island, they are representative of the trends seen at other sites in Lake Vermilion.

Historical Secchi data from all monitoring sites in Lake Vermilion will be tabulated here in the future.

Carlson Trophic State Index

The Minnesota PCA has developed an overall assessment of Lake Vermilion's trophic status based on measurements of phosphorus and chlorophyll-a levels from the 2000 Lake Assessment Report and on recent Secchi disk data (see above). The Carlson Trophic State Indices computed from each of those methods are in close agreement, ranging from 46 to 51 (on a scale that ranges from 20 to 80). That places Lake Vermilion midway between the mesotrophic and eutrophic states.

For more detail on what the trophic state means and on the underlying data, click here.

For More Information or to Volunteer  

For more information on our water quality monitoring or to volunteer to assist in this ongoing effort, please contact activity coordinator Mel Hintz [contact info].