Flambeau Lake Deep

On the LakeGrade rubric, Flambeau Lake Deep pulls an A: clarity at 42.7 ft and phosphorus readings still being added put it in the top bracket for Wisconsin. Sub-grades cluster within a single letter of each other, which usually means the lake is in stable trophic balance rather than fighting one specific stressor.

A TSI value of 23 puts Flambeau Lake Deep in the oligotrophic range, where biological productivity stays low and the water column remains clear. Flambeau Lake Deep is unusually deep for Wisconsin at 78 ft, which buffers the lake against summer warming and helps the deep water stay oxygenated. Flambeau Lake Deep covers 1,166 acres alongside partial shoreline records, large enough that conditions can vary meaningfully between bays. Within Vilas County's 202 graded lakes, Flambeau Lake Deep ranks 120 — below the local median, though not at the bottom.

Flambeau Lake Deep has at least one documented invasive species (Purple Loosestrife), so boaters and anglers should observe clean-drain-dry steps when leaving the lake. The fishery includes walleye alongside the lake's other 6 documented species — a notable draw for Wisconsin anglers. 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.