Ashippun Lake

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

The lake's low TSI puts it in oligotrophic territory — the cleanest of the four trophic classes, but also the most vulnerable to nutrient-driven shifts. The lake bottoms out at 35 ft — a moderate depth that supports a warm-water fishery without the year-round cold refuge a deeper basin provides. Ashippun Lake is small — 94 acres alongside partial shoreline records — which makes it sensitive to even modest changes in watershed runoff or recreational pressure. Ashippun Lake ranks 19 of 48 in Waukesha County — solidly in the upper half of the local distribution.

Zebra mussel presence at Ashippun Lake means the lake's clarity numbers carry an asterisk — filtered water is not the same as nutrient-poor water. Walleye are documented at Ashippun Lake, one of 4 fish species on record for the lake. A documented public access point at Ashippun Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. 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.