Birch Lake

The LakeGrade rubric puts Birch Lake at a C: clarity at 3.9 ft, 21 µg/L of phosphorus, and a TSI of 53 signal an intermediate trophic state. The lake's weakest score is on Secchi depth — the water looks more turbid than its phosphorus number alone would predict.

At a TSI of 53, Birch Lake reads as eutrophic — nutrient-rich enough that summer algal growth and reduced clarity are expected, not unusual. A maximum depth of 25 ft puts Birch Lake in the middle of Minnesota's depth distribution. At 7,074 acres, Birch Lake is one of the larger lakes in St. Louis County, with 90.1 miles of shoreline supporting multiple distinct use patterns. Birch Lake ranks 93 of 187 in St. Louis County — solidly in the upper half of the local distribution.

Birch 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 Birch Lake, one of 10 fish species on record for the lake. A documented public access point at Birch Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. 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.