Duck Lake

Duck Lake earns an F: 105 µg/L of phosphorus and clarity at 2.8 ft signal heavy nutrient loading from the surrounding watershed. 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.

At a TSI of 67, Duck Lake reads as eutrophic — nutrient-rich enough that summer algal growth and reduced clarity are expected, not unusual. The lake bottoms out at 25 ft — a moderate depth that supports a warm-water fishery without the year-round cold refuge a deeper basin provides. Duck Lake covers 290 acres alongside 2.7 miles of shoreline — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins. Within the 9 graded lakes of Blue Earth County, Duck Lake sits at rank 8, near the bottom of the county list.

Duck Lake has no invasive species recorded in Minnesota state databases as of 2024, though prevention practices still apply at all access points. The fishery includes walleye alongside the lake's other 17 documented species — a notable draw for Minnesota anglers. Public access is available — the lake is on the Minnesota PCA public-access list. The lake has a long ice-out record — 41 observations on file, with a median ice-out around Apr 4. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.