Hartlaub Lake

Hartlaub Lake carries a solid B grade — strong on most parameters, with measurements that hold up well across the summer season. Phosphorus is the parameter holding the grade back — runoff from the surrounding watershed appears to keep nutrient levels elevated through the summer.

The lake sits in the mesotrophic zone — the band where most well-managed Wisconsin lakes fall. 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. Public access is available — the lake is on the Wisconsin DNR public-access list. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.