Bear Trap Lake

On the LakeGrade scale Bear Trap Lake grades a B, with clarity at 8.8 ft and 25 µg/L of phosphorus placing it above the Wisconsin median. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

A TSI near 48 places Bear Trap Lake in the mesotrophic band — moderate productivity, with seasonal swings between clearer spring water and richer late-summer conditions. A maximum depth of 25 ft puts Bear Trap Lake in the middle of Wisconsin's depth distribution. The lake's 247 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. Among the 74 graded lakes in Polk County, Bear Trap Lake sits at rank 32, above the county median.

Zebra mussel presence at Bear Trap Lake means the lake's clarity numbers carry an asterisk — filtered water is not the same as nutrient-poor water. The fishery includes walleye alongside the lake's other 5 documented species — a notable draw for Wisconsin anglers. Public access is available — the lake is on the Wisconsin DNR public-access list. 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.