Sylvan Lake
Hennepin County, MinnesotaHypereutrophic
Sylvan Lake earns an F: 301 µg/L of phosphorus and clarity at 1.1 ft signal heavy nutrient loading from the surrounding watershed. clarity and phosphorus rate similarly, so there is no obvious single lever to pull on watershed management.
Hypereutrophic conditions mean the lake is operating at the upper end of the productivity scale, with all the bloom risk that implies. 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. Sylvan Lake ranks 79 of 95 in Hennepin County — at the lower end of the locally monitored distribution.
No invasive species are currently listed at Sylvan Lake — the lake remains off the Minnesota infested-waters roster. The state fisheries records do not list documented species for Sylvan Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. No formal public access is documented at Sylvan Lake — most use is by shoreline residents and their guests. 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.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2023-10-03. Grade methodology: LakeGrade methodology.
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Swimming Safety
Avoid swimming, very poor water quality, potential algae toxins
Water Quality Grade: F, Very Poor
Very murky, less than 1.1 ft of visibility. Phosphorus level: 301.1 µg/L. Trophic State Index: 81.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.1 ft | F |
| Phosphorus | 301.1 µg/L | F |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 81 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Location
County Ranking
Ranked #79 of 95 lakes in Hennepin County
Cleaner Lakes Within 30 Miles
Sylvan Lake holds Grade F. 2 nearby lakes hold higher grades.
- CBeebe LakeWright County · mi · Two grade letters higher (F → C)
- DSchwappauf LakeHennepin County · mi · Higher grade (F → D)
Nearby Lakes in Hennepin County
More Minnesota Lake Rankings
State Parks Near Sylvan Lake
Other Grade F Lakes in Minnesota
EPA Impairment Status
Sylvan 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 MN27-0171-00 · Official waterbody report
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: 2023-10-03
Monitoring stations: 1