Kohlman Lake

Kohlman Lake earns an F: 94 µg/L of phosphorus and clarity at 3.3 ft signal heavy nutrient loading from the surrounding watershed. 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.

Eutrophic conditions are the baseline here: clarity drops noticeably in late summer, and dissolved oxygen near the bottom can become a concern. Kohlman Lake is a shallow lake at 9 ft maximum depth, which means it warms quickly, mixes constantly, and amplifies nutrient inputs. Kohlman Lake is small — 84 acres alongside 1.8 miles of shoreline — which makes it sensitive to even modest changes in watershed runoff or recreational pressure. Within the 49 graded lakes of Ramsey County, Kohlman Lake sits at rank 47, near the bottom of the county list.

Zebra mussel presence at Kohlman Lake means the lake's clarity numbers carry an asterisk — filtered water is not the same as nutrient-poor water. Walleye are documented at Kohlman Lake, one of 11 fish species on record for the lake. No formal public access is documented at Kohlman Lake — most use is by shoreline residents and their guests. The lake has a long ice-out record — 30 observations on file, with a median ice-out around Apr 1. 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.