Barnum Lake

Barnum 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.

A TSI value of 36 puts Barnum Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. Barnum Lake reaches 30 ft at its deepest point — typical for Minnesota mid-sized lakes, with seasonal stratification but limited cold-water refuge. The lake's 151 acres and 4.5 miles of shoreline put it in the mid-range bucket — large enough for varied use, small enough that watershed inputs reach the whole basin. Among the 133 graded lakes in Cass County, Barnum Lake ranks 28 — in the top quartile locally.

Barnum Lake has no invasive species recorded in Minnesota state databases as of 2024, though prevention practices still apply at all access points. The fishery is bass-led, with 8 documented species across the lake's records. The lake lacks a documented public access point, so visitor use is limited. Ice-out has been logged at Barnum Lake more than two dozen times, putting the median around Apr 17 — 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.