Martha Lake

On the LakeGrade rubric, Martha Lake pulls an A: clarity at 26.2 ft and phosphorus readings still being added put it in the top bracket for 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 30 puts Martha Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. At 55 ft of maximum depth, Martha Lake stratifies reliably through the summer — the hypolimnion stays cooler and clearer than the surface layer suggests. At 146 acres, Martha Lake fits the Wisconsin median for monitored lakes, with partial shoreline records. Martha Lake sits at rank 20 of 34 in Iron County, in the lower half of the local distribution.

No invasive species are currently listed at Martha Lake — the lake remains off the Wisconsin infested-waters roster. Walleye are documented at Martha Lake, one of 6 fish species on record for the lake. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.