Mason Lake

Mason Lake grades an F: every scored parameter (clarity and phosphorus) rates poorly, placing it among the most stressed lakes monitored in Wisconsin. clarity and phosphorus rate similarly, so there is no obvious single lever to pull on watershed management.

The hypereutrophic status — TSI 73 — reflects sustained heavy nutrient loading from the surrounding watershed and frequent algal pressure. 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 19 of 19 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. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.