Otter Lake

Otter Lake earns an A — water clarity, phosphorus, and chlorophyll-a all rate among the best monitored waters in Waupaca County. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

A TSI value of 33 puts Otter Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. The lake bottoms out at 40 ft — a moderate depth that supports a warm-water fishery without the year-round cold refuge a deeper basin provides. Otter Lake is small — 15 acres alongside partial shoreline records — which makes it sensitive to even modest changes in watershed runoff or recreational pressure. Among the 27 graded lakes in Waupaca County, Otter Lake sits at rank 11, above the county median.

Eurasian watermilfoil is established at Otter Lake, which can dampen recreational access and pressure the native plant community. Walleye are documented at Otter Lake, one of 4 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.