Hartlaub Lake

Hartlaub Lake earns a C — middle-of-the-pack water quality, with one or two parameters dragging the average down from a stronger grade. The two scored sub-grades — clarity and phosphorus — track close together, so neither one is dragging the average down.

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. Hartlaub Lake is unusually deep for Wisconsin at 60 ft, which buffers the lake against summer warming and helps the deep water stay oxygenated. Hartlaub Lake is small — 37 acres alongside partial shoreline records — which makes it sensitive to even modest changes in watershed runoff or recreational pressure. Hartlaub Lake sits at rank 11 of 18 in Manitowoc County, in the lower half of the local distribution.

Eurasian watermilfoil has been documented at Hartlaub Lake, requiring shoreline management to keep dense mats from crowding native vegetation. The fishery is bass-led, with 3 documented species across the lake's records. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.