Black Oak Lake

The LakeGrade rubric puts Black Oak Lake at a C: clarity at 9.5 ft, phosphorus readings still being added, and a TSI of 45 signal an intermediate trophic state. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

Mesotrophic conditions dominate at Black Oak Lake: enough nutrients for a healthy fishery, not so much that algal blooms become a chronic problem. Black Oak Lake reaches 19 ft at its deepest point — typical for Minnesota mid-sized lakes, with seasonal stratification but limited cold-water refuge. The lake is compact at 95 acres, with 3.4 miles of shoreline and little volume to buffer nutrient inputs. Black Oak Lake ranks 27 of 55 in Stearns County — solidly in the upper half of the local distribution.

Black Oak Lake has no invasive species recorded in Minnesota state databases as of 2024, though prevention practices still apply at all access points. Walleye are documented at Black Oak Lake, one of 9 fish species on record for the lake. Public access is available — the lake is on the Minnesota PCA public-access list. 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.