Olson Lake

On the LakeGrade rubric Olson Lake fails the cutoffs — a TSI of 92 and persistent algal pressure put it in the bottom tier. The two scored sub-grades — clarity and phosphorus — track close together, so neither one is dragging the average down.

The hypereutrophic status — TSI 92 — reflects sustained heavy nutrient loading from the surrounding watershed and frequent algal pressure. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. The lake's surface area is not consistently recorded across state datasets — physical context remains partial. Olson Lake ranks 9 of 9 in Big Stone County — at the lower end of the locally monitored distribution.

Olson Lake has no invasive species recorded in Minnesota state databases as of 2023, though prevention practices still apply at all access points. The state fisheries records do not list documented species for Olson Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. No formal public access is documented at Olson Lake — most use is by shoreline residents and their guests. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.