Flour Lake

Flour 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.

Trophically, Flour Lake reads as oligotrophic — nutrient-poor, clear, and ecologically more sensitive to disturbance than richer lakes. At 75 ft of maximum depth, Flour Lake stratifies reliably through the summer — the hypolimnion stays cooler and clearer than the surface layer suggests. Flour Lake covers 330 acres alongside 8.5 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, Flour Lake ranks 16 — in the top quartile locally.

An invasive species record — spiny waterflea — has been logged at Flour Lake; Minnesota PCA maintains the official infested-waters list. The fishery includes walleye alongside the lake's other 9 documented species — a notable draw for Minnesota anglers. A documented public access point at Flour Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. 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.