Turtle-Flambeau Flowage Lake

Turtle-Flambeau Flowage Lake earns a D — measurements through 2023 show persistent nutrient pressure that limits clarity through the summer. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

At a TSI of 57, Turtle-Flambeau Flowage Lake reads as eutrophic — nutrient-rich enough that summer algal growth and reduced clarity are expected, not unusual. The lake's 50 ft maximum depth is in the upper tier for Wisconsin — deep enough for cold-water fish to find refuge in summer. Turtle-Flambeau Flowage Lake covers 12,942 acres alongside partial shoreline records, large enough that conditions can vary meaningfully between bays. Turtle-Flambeau Flowage Lake ranks 31 of 33 in Iron County — at the lower end of the locally monitored distribution.

Eurasian watermilfoil is established at Turtle-Flambeau Flowage Lake, which can dampen recreational access and pressure the native plant community. The fishery includes walleye alongside the lake's other 7 documented species — a notable draw for Wisconsin anglers. Public access is available — the lake is on the Wisconsin DNR public-access list. 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.