Pepin Lake

Pepin Lake earns an F: phosphorus readings still being added and clarity at 1.6 ft signal heavy nutrient loading from the surrounding watershed. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

The hypereutrophic status — TSI 71 — reflects sustained heavy nutrient loading from the surrounding watershed and frequent algal pressure. The lake's 60 ft maximum depth is in the upper tier for Wisconsin — deep enough for cold-water fish to find refuge in summer. Pepin Lake covers 24,550 acres alongside partial shoreline records, large enough that conditions can vary meaningfully between bays.

Zebra mussel presence at Pepin Lake means the lake's clarity numbers carry an asterisk — filtered water is not the same as nutrient-poor water. The fishery is bass-led, with 3 documented species across the lake's records. Public access is available — the lake is on the Wisconsin DNR public-access list. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.