Kettle Moraine Lake

On the LakeGrade rubric, Kettle Moraine Lake pulls an A: clarity at 36.1 ft and 16 µg/L of phosphorus put it in the top bracket for Wisconsin. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

A TSI value of 35 puts Kettle Moraine Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. The lake bottoms out at 30 ft — a moderate depth that supports a warm-water fishery without the year-round cold refuge a deeper basin provides. At 209 acres, Kettle Moraine Lake fits the Wisconsin median for monitored lakes, with partial shoreline records. Among the 10 graded lakes in Fond du Lac County, Kettle Moraine Lake sits at rank 3, above the county median.

Zebra mussels have been documented at Kettle Moraine Lake, which alters the filter-feeding balance and can paradoxically increase water clarity while disrupting the food web. Walleye are documented at Kettle Moraine Lake, one of 4 fish species on record for the lake. 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.