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C

Seed Lake

Unknown County, MinnesotaLimited DataMesotrophic

Seed Lake earns a C — middle-of-the-pack water quality, with one or two parameters dragging the average down from a stronger grade. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

The lake sits in the mesotrophic zone — the band where most well-managed Minnesota lakes fall. 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. Within the 5 graded lakes of Unknown County, Seed Lake sits at rank 5, near the bottom of the county list.

No invasive species are currently listed at Seed Lake — the lake remains off the Minnesota infested-waters roster. The state fisheries records do not list documented species for Seed Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. The lake lacks a documented public access point, so visitor use is limited. 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 2025-07-09. Grade methodology: LakeGrade methodology.

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Swimming Safety

Generally safe for swimming, moderate water quality

Water Quality Grade: C, Fair

Moderate clarity, visible to about 7 ft. Trophic State Index: 49.

MetricValueGrade
Water Clarity (Secchi Depth)7 ftC
PhosphorusNo data
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)49Mesotrophic

Moderate nutrients, good water quality

Water Quality Trend: Stable

Based on 5 years of monitoring data (2020-2025).

MetricTrendChange/YearYears
Water Clarity Stable+0.003 m/yr5
See year-by-year chart →

Location

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County Ranking

Ranked #5 of 5 lakes in Unknown County

Nearby Lakes in Unknown County

EPA Impairment Status

Seed Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).

Causes of impairment

Mercury

A Total Maximum Daily Load (TMDL) plan has been approved.

Source: EPA ATTAINS assessment unit MN38-0491-00 · Official waterbody report · Matched by proximity (2 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: 2025-07-09

Monitoring stations: 5

Where to stay near Seed Lake

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