Thomas Lake

On the LakeGrade rubric, Thomas Lake pulls an A: clarity at 15.0 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.

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 28 ft — a moderate depth that supports a warm-water fishery without the year-round cold refuge a deeper basin provides. Thomas Lake is small — 32 acres alongside partial shoreline records — which makes it sensitive to even modest changes in watershed runoff or recreational pressure. Among the 28 graded lakes in Portage County, Thomas Lake ranks 5 — in the top quartile locally.

Eurasian watermilfoil has been documented at Thomas Lake, requiring shoreline management to keep dense mats from crowding native vegetation. The fishery is bass-led, with 4 documented species across the lake's records. 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.