Clay Lake

Clay Lake sits at the top of the Wisconsin DNR grading rubric with an A, a mark reached by the cleanest lakes in Wisconsin. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

A TSI near 44 places Clay Lake in the mesotrophic band — moderate productivity, with seasonal swings between clearer spring water and richer late-summer conditions. A maximum depth of 45 ft puts Clay Lake in the middle of Wisconsin's depth distribution. At 28 acres, Clay Lake sits below the Wisconsin median: a small water where shoreline activity has an outsized effect on water quality. Within the 55 graded lakes of Bayfield County, Clay Lake sits at rank 46, near the bottom of the county list.

Clay Lake has no invasive species recorded in Wisconsin state databases as of 2023, though prevention practices still apply at all access points. Bass fishing is part of the appeal: the species list runs to 2, anchored by largemouth and/or smallmouth bass. 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.