Duck Lake
Hennepin County, MinnesotaEutrophic
The LakeGrade rubric puts Duck Lake at a C: clarity at 6.2 ft, 34 µg/L of phosphorus, and a TSI of 53 signal an intermediate trophic state. The two scored sub-grades — clarity and phosphorus — track close together, so neither one is dragging the average down.
Eutrophic conditions are the baseline here: clarity drops noticeably in late summer, and dissolved oxygen near the bottom can become a concern. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. The lake's surface area is not consistently recorded across state datasets — physical context remains partial. Duck Lake ranks 29 of 95 in Hennepin County — solidly in the upper half of the local distribution.
Duck Lake carries an invasive watermilfoil record — boat-launch decontamination and shoreline care matter more here than at uninfested lakes. The state fisheries records do not list documented species for Duck Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. No formal public access is documented at Duck Lake — most use is by shoreline residents and their guests. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2023-09-14. Grade methodology: LakeGrade methodology.
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Swimming Safety
Generally safe for swimming, moderate water quality
Water Quality Grade: C, Fair
Murky, only visible to about 6.2 ft. Phosphorus level: 34 µg/L. Trophic State Index: 53.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 6.2 ft | D |
| Phosphorus | 34 µg/L | C |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 53 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
Water Quality Trend: ↑ Improving
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.029 m/yr | 3 |
| Phosphorus | ↑ Improving | -3.11 µg/L/yr | 3 |
Location
County Ranking
Ranked #29 of 95 lakes in Hennepin County
Cleaner Lakes Within 30 Miles
Duck Lake holds Grade C. 2 nearby lakes hold higher grades.
- CRound LakeHennepin County · mi · Higher overall water quality score
- CRice Marsh LakeHennepin County · mi · Higher overall water quality score
Nearby Lakes in Hennepin County
More Minnesota Lake Rankings
State Parks Near Duck Lake
Other Grade C Lakes in Minnesota
Eutrophic Lakes in Minnesota
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Duck Lake. 1 report on file.
- —Fish Stocking History — DuckFish Stocking History · MN DNR LakeFinder
EPA Impairment Status
Duck Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN27-0071-00 · Official waterbody report · Matched by proximity (1.16 km)
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Grading methodology based on Metropolitan Council standards
Most recent sample: 2023-09-14
Monitoring stations: 1