Mule Lake

Mule Lake sits at the top of the Minnesota PCA grading rubric with an A, a mark reached by the cleanest lakes in Minnesota. clarity and phosphorus rate similarly, so there is no obvious single lever to pull on watershed management.

The lake's low TSI puts it in oligotrophic territory — the cleanest of the four trophic classes, but also the most vulnerable to nutrient-driven shifts. Mule Lake reaches 31 ft at its deepest point — typical for Minnesota mid-sized lakes, with seasonal stratification but limited cold-water refuge. At 53 acres, Mule Lake sits below the Minnesota median: a small water where shoreline activity has an outsized effect on water quality. Among the 97 graded lakes in Otter Tail County, Mule Lake ranks 23 — in the top quartile locally.

No invasive species are currently listed at Mule Lake — the lake remains off the Minnesota infested-waters roster. The state fisheries records do not list documented species for Mule Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. The lake lacks a documented public access point, so visitor use is limited. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.