Karl Lake

Karl Lake earns a C — middle-of-the-pack water quality, with one or two parameters dragging the average down from a stronger grade. 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.

Mesotrophic conditions dominate at Karl Lake: enough nutrients for a healthy fishery, not so much that algal blooms become a chronic problem. Karl Lake is unusually deep for Minnesota at 70 ft, which buffers the lake against summer warming and helps the deep water stay oxygenated. The lake's 121 acres and 5.4 miles of shoreline put it in the mid-range bucket — large enough for varied use, small enough that watershed inputs reach the whole basin. Within Cook County's 128 graded lakes, Karl Lake ranks 85 — below the local median, though not at the bottom.

Karl Lake has no invasive species recorded in Minnesota state databases as of 2022, though prevention practices still apply at all access points. The state fisheries records do not list documented species for Karl 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. 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.