Mallard Lake

Mallard Lake sits at the top of the Wisconsin DNR grading rubric with an A, a mark reached by the cleanest lakes in Wisconsin. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

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. Mallard Lake is a shallow lake at 10 ft maximum depth, which means it warms quickly, mixes constantly, and amplifies nutrient inputs. The lake is compact at 16 acres, with partial shoreline records and little volume to buffer nutrient inputs. Mallard Lake ranks 4 of 15 in Milwaukee County — solidly in the upper half of the local distribution.

Eurasian watermilfoil has been documented at Mallard Lake, requiring shoreline management to keep dense mats from crowding native vegetation. 1 fish species are documented at Mallard Lake, a mixed warm-water community typical for Wisconsin lakes of this size. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.