Lake Mallalieu

Lake Mallalieu earns a C — middle-of-the-pack water quality, with one or two parameters dragging the average down from a stronger grade. 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. Lake Mallalieu reaches 17 ft at its deepest point — typical for Wisconsin mid-sized lakes, with seasonal stratification but limited cold-water refuge. At 289 acres, Lake Mallalieu fits the Wisconsin median for monitored lakes, with partial shoreline records. Within St. Croix County's 7 graded lakes, Lake Mallalieu ranks 4 — below the local median, though not at the bottom.

Eurasian watermilfoil has been documented at Lake Mallalieu, requiring shoreline management to keep dense mats from crowding native vegetation. Bass fishing is part of the appeal: the species list runs to 4, anchored by largemouth and/or smallmouth bass. A documented public access point at Lake Mallalieu makes the lake usable for shore fishing, paddle craft, and trailered boats. Monitoring depth is thin here: the LakeGrade rubric is applied to a small number of sample years, and the grade will be revised as more data accumulates.