Pepin Lake

On the LakeGrade rubric Pepin Lake fails the cutoffs — a TSI of 61 and persistent algal pressure put it in the bottom tier. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

At a TSI of 61, Pepin Lake reads as eutrophic — nutrient-rich enough that summer algal growth and reduced clarity are expected, not unusual. At 60 ft of maximum depth, Pepin Lake stratifies reliably through the summer — the hypolimnion stays cooler and clearer than the surface layer suggests. With 12,299 acres of surface and 54.9 miles of shoreline, Pepin Lake is a large water by Minnesota standards — recreational pressure is spread across a long shoreline.

Pepin Lake is on the Minnesota infested-waters list for zebra mussels — boaters should follow clean-drain-dry protocols when moving gear to or from the lake. Walleye are documented at Pepin Lake, one of 47 fish species on record for the lake. A documented public access point at Pepin Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. Ice-out has been logged at Pepin Lake more than two dozen times, putting the median around Mar 29 — a useful baseline for tracking climate trends. 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.