Mason Lake

Mason Lake pulls a D on the LakeGrade rubric — phosphorus loading and limited clarity hold it below the Wisconsin average. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

At a TSI of 64, Mason Lake reads as eutrophic — nutrient-rich enough that summer algal growth and reduced clarity are expected, not unusual. Mason Lake is a shallow lake at 9 ft maximum depth, which means it warms quickly, mixes constantly, and amplifies nutrient inputs. Mason Lake covers 882 acres alongside partial shoreline records — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins. Mason Lake ranks 20 of 20 in Adams County — at the lower end of the locally monitored distribution.

Eurasian watermilfoil is established at Mason Lake, which can dampen recreational access and pressure the native plant community. Bass fishing is part of the appeal: the species list runs to 5, anchored by largemouth and/or smallmouth bass. 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.