Delavan Lake

The LakeGrade rubric puts Delavan Lake at a C: clarity at 8.0 ft, 50 µg/L of phosphorus, and a TSI of 54 signal an intermediate trophic state. Sub-grades cluster within a single letter of each other, which usually means the lake is in stable trophic balance rather than fighting one specific stressor.

A TSI in the eutrophic range signals a lake doing what nutrient-loaded waters do — supporting an active algal community at the cost of clear water. 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 35 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.