Big Eau Pleine Lake

Big Eau Pleine Lake grades an F: every scored parameter (clarity and phosphorus) rates poorly, placing it among the most stressed lakes monitored in Wisconsin. With clarity and phosphorus scored, the sub-grades cluster within a letter of each other, pointing to stable conditions rather than one specific stressor.

The hypereutrophic status — TSI 73 — reflects sustained heavy nutrient loading from the surrounding watershed and frequent algal pressure. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. The lake's surface area is not consistently recorded across state datasets — physical context remains partial. Big Eau Pleine Lake ranks 4 of 5 in Marathon County — at the lower end of the locally monitored distribution.

Big Eau Pleine Lake has no invasive species recorded in Wisconsin state databases as of 2025, though prevention practices still apply at all access points. The state fisheries records do not list documented species for Big Eau Pleine Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.