Delavan Lake

On the LakeGrade scale Delavan Lake grades a B, with clarity at 24.8 ft and 50 µg/L of phosphorus placing it above the Wisconsin median. High phosphorus is the leading drag on the score — likely from upland agriculture, lawn runoff, or in-lake sediment release.

The lake sits in the mesotrophic zone — the band where most well-managed Wisconsin lakes fall. At 52 ft of maximum depth, Delavan Lake stratifies reliably through the summer — the hypolimnion stays cooler and clearer than the surface layer suggests. Delavan Lake covers 1,906 acres alongside partial shoreline records, large enough that conditions can vary meaningfully between bays. Delavan Lake sits at rank 20 of 34 in Walworth County, in the lower half of the local distribution.

Delavan Lake is on the Wisconsin infested-waters list for zebra mussels — boaters should follow clean-drain-dry protocols when moving gear to or from the lake. Walleye are documented at Delavan Lake, one of 6 fish species on record for the lake. A documented public access point at Delavan Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.