Upper Gresham Lake

Upper Gresham 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.

A TSI near 42 places Upper Gresham Lake in the mesotrophic band — moderate productivity, with seasonal swings between clearer spring water and richer late-summer conditions. A maximum depth of 32 ft puts Upper Gresham Lake in the middle of Wisconsin's depth distribution. At 362 acres, Upper Gresham Lake fits the Wisconsin median for monitored lakes, with partial shoreline records. Upper Gresham Lake ranks 78 of 191 in Vilas County — solidly in the upper half of the local distribution.

Eurasian watermilfoil is established at Upper Gresham Lake, which can dampen recreational access and pressure the native plant community. The fishery includes walleye alongside the lake's other 5 documented species — a notable draw for Wisconsin anglers. Public access is available — the lake is on the Wisconsin DNR public-access list. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.