Tonseth Lake

Tonseth Lake carries a solid B grade — strong on most parameters, with measurements that hold up well across the summer season. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

The lake sits in the mesotrophic zone — the band where most well-managed Minnesota lakes fall. A maximum depth of 27 ft puts Tonseth Lake in the middle of Minnesota's depth distribution. Tonseth Lake covers 149 acres alongside 3.2 miles of shoreline — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins. Among the 97 graded lakes in Otter Tail County, Tonseth Lake sits at rank 46, above the county median.

No invasive species are currently listed at Tonseth Lake — the lake remains off the Minnesota infested-waters roster. Walleye are documented at Tonseth Lake, one of 12 fish species on record for the lake. No formal public access is documented at Tonseth Lake — most use is by shoreline residents and their guests. Ice-out has been logged at Tonseth Lake more than two dozen times, putting the median around Apr 15 — a useful baseline for tracking climate trends. 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.