Swan Lake

Swan 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. Swan Lake is unusually deep for Wisconsin at 82 ft, which buffers the lake against summer warming and helps the deep water stay oxygenated. Swan Lake covers 407 acres alongside partial shoreline records — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins. Among the 10 graded lakes in Columbia County, Swan Lake ranks 1 — in the top quartile locally.

Eurasian watermilfoil has been documented at Swan Lake, requiring shoreline management to keep dense mats from crowding native vegetation. Walleye are documented at Swan Lake, one of 5 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.