Prairie Lake

Prairie Lake pulls a D on the LakeGrade rubric — phosphorus loading and limited clarity hold it below the Minnesota average.

Eutrophic conditions are the baseline here: clarity drops noticeably in late summer, and dissolved oxygen near the bottom can become a concern. A maximum depth of 47 ft puts Prairie Lake in the middle of Minnesota's depth distribution. The lake's 794 acres and 8.2 miles of shoreline put it in the mid-range bucket — large enough for varied use, small enough that watershed inputs reach the whole basin. Within the 187 graded lakes of St. Louis County, Prairie Lake sits at rank 158, near the bottom of the county list.

Prairie Lake has no invasive species recorded in Minnesota state databases as of 2024, though prevention practices still apply at all access points. Walleye are documented at Prairie Lake, one of 15 fish species on record for the lake. Public access is available — the lake is on the Minnesota PCA public-access list. Monitoring depth is thin here: the LakeGrade rubric is applied to a small number of sample years, and the grade will be revised as more data accumulates.