Tree Lake

Tree Lake sits at the top of the Wisconsin DNR grading rubric with an A, a mark reached by the cleanest lakes in Wisconsin. 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. Tree Lake reaches 33 ft at its deepest point — typical for Wisconsin mid-sized lakes, with seasonal stratification but limited cold-water refuge. At 73 acres, Tree Lake sits below the Wisconsin median: a small water where shoreline activity has an outsized effect on water quality. Tree Lake ranks 22 of 29 in Portage County — at the lower end of the locally monitored distribution.

An invasive species record — Banded Mystery Snail — has been logged at Tree Lake; Wisconsin DNR maintains the official infested-waters list. The fishery is bass-led, with 3 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.