Lower Eau Claire Lake

Lower Eau Claire 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 value of 35 puts Lower Eau Claire Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. Lower Eau Claire Lake reaches 41 ft at its deepest point — typical for Wisconsin mid-sized lakes, with seasonal stratification but limited cold-water refuge. Lower Eau Claire Lake covers 784 acres alongside partial shoreline records — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins. Within Bayfield County's 52 graded waters, Lower Eau Claire Lake sits at rank 9, near the top of the local distribution.

Lower Eau Claire Lake has at least one documented invasive species (Banded Mystery Snail), so boaters and anglers should observe clean-drain-dry steps when leaving the lake. The fishery includes walleye alongside the lake's other 6 documented species — a notable draw for Wisconsin anglers. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.