Deep Lake

Deep Lake sits at the top of the Minnesota PCA grading rubric with an A, a mark reached by the cleanest lakes in Minnesota. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

Trophically, Deep Lake reads as oligotrophic — nutrient-poor, clear, and ecologically more sensitive to disturbance than richer lakes. Deep Lake is unusually deep for Minnesota at 50 ft, which buffers the lake against summer warming and helps the deep water stay oxygenated. At 73 acres, Deep Lake sits below the Minnesota median: a small water where shoreline activity has an outsized effect on water quality. Within St. Louis County's 187 graded waters, Deep Lake sits at rank 19, near the top of the local distribution.

Deep Lake has no invasive species recorded in Minnesota state databases as of 2022, though prevention practices still apply at all access points. The fishery includes walleye alongside the lake's other 10 documented species — a notable draw for Minnesota anglers. 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.