Clark Lake

Clark Lake earns an A — water clarity, phosphorus, and chlorophyll-a all rate among the best monitored waters in Door County. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

A TSI value of 31 puts Clark Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. A maximum depth of 25 ft puts Clark Lake in the middle of Wisconsin's depth distribution. The lake's 865 acres and partial shoreline records put it in the mid-range bucket — large enough for varied use, small enough that watershed inputs reach the whole basin. Clark Lake ranks 1 of 11 in Door County, putting it in the upper tier of locally monitored lakes.

Zebra mussels have been documented at Clark Lake, which alters the filter-feeding balance and can paradoxically increase water clarity while disrupting the food web. Walleye are documented at Clark Lake, one of 6 fish species on record for the lake. Public access is available — the lake is on the Wisconsin DNR public-access list. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.