Big Falls Flowage Lake

Big Falls Flowage Lake sits at the top of the Wisconsin DNR grading rubric with an A, a mark reached by the cleanest lakes in 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.

The lake's low TSI puts it in oligotrophic territory — the cleanest of the four trophic classes, but also the most vulnerable to nutrient-driven shifts. The lake bottoms out at 45 ft — a moderate depth that supports a warm-water fishery without the year-round cold refuge a deeper basin provides. At 281 acres, Big Falls Flowage Lake fits the Wisconsin median for monitored lakes, with partial shoreline records. Among the 13 graded lakes in Rusk County, Big Falls Flowage Lake sits at rank 4, above the county median.

Eurasian watermilfoil is established at Big Falls Flowage Lake, which can dampen recreational access and pressure the native plant community. Walleye are documented at Big Falls Flowage Lake, one of 8 fish species on record for the lake. 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.