Birch Lake

Birch Lake sits at the top of the Minnesota PCA grading rubric with an A, a mark reached by the cleanest lakes in Minnesota. Sub-grades cluster within a single letter of each other, which usually means the lake is in stable trophic balance rather than fighting one specific stressor.

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. The lake's 69 ft maximum depth is in the upper tier for Minnesota — deep enough for cold-water fish to find refuge in summer. Birch Lake covers 236 acres alongside 6.7 miles of shoreline — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins. Among the 128 graded lakes in Cook County, Birch Lake ranks 2 — in the top quartile locally.

No invasive species are currently listed at Birch Lake — the lake remains off the Minnesota infested-waters roster. Bass fishing is part of the appeal: the species list runs to 3, anchored by largemouth and/or smallmouth bass. 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.