Plum Lake

Plum Lake earns an A — water clarity, phosphorus, and chlorophyll-a all rate among the best monitored waters in Vilas County. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

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. Plum Lake is unusually deep for Wisconsin at 57 ft, which buffers the lake against summer warming and helps the deep water stay oxygenated. Plum Lake covers 1,057 acres alongside partial shoreline records, large enough that conditions can vary meaningfully between bays. Among the 202 graded lakes in Vilas County, Plum Lake sits at rank 95, above the county median.

Eurasian watermilfoil has been documented at Plum Lake, requiring shoreline management to keep dense mats from crowding native vegetation. 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. 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.