St. Johns Lake

On the LakeGrade rubric, St. Johns Lake pulls an A: clarity at 33.5 ft and 15 µg/L of phosphorus put it in the top bracket for Wisconsin. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

Trophically, St. Johns Lake reads as oligotrophic — nutrient-poor, clear, and ecologically more sensitive to disturbance than richer lakes. St. Johns Lake reaches 21 ft at its deepest point — typical for Wisconsin mid-sized lakes, with seasonal stratification but limited cold-water refuge. The lake's 107 acres and partial shoreline records put it in the mid-range bucket — large enough for varied use, small enough that watershed inputs reach the whole basin. Among the 35 graded lakes in Forest County, St. Johns Lake sits at rank 17, above the county median.

No invasive species are currently listed at St. Johns Lake — the lake remains off the Wisconsin infested-waters roster. Walleye are documented at St. Johns Lake, one of 3 fish species on record for the lake. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.