Decatur Lake
Green County, Wisconsin109 acresView mapDirections
No nutrient or algae sampling on record from Wisconsin DNR for this lake.
- Impaired · Nutrients (phosphorus, nitrogen)
- 10 ft max depth
Decatur Lake in Green County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Maximum depth: 10 ft. Surface area: 109 acres.
Decatur Lake is a 109-acre lake in Green County, Wisconsin with a maximum depth of 10 feet.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water. Methodology: how these readings are compared.
Swimming conditions
No readingRecreation use not supported
Nutrient and algae readings are not a swimming clearance. Decatur Lake is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Decatur Lake is safe to swim in today is a call for the Wisconsin Department of Natural Resources and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Decatur Lake
These are the measurements Wisconsin DNR publishes for Decatur Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data. TSI undefined.
Ask about Decatur Lake
Answers come straight from the public measurements and survey records on this page.
DNR Reports & Resources
Wisconsin DNR Fisheries scientists publish multi-year survey reports for Decatur Lake covering fish populations, stocking, water quality, and management. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- 2025Decatur Lake spring shocking survey, 2025Spring Shocking Survey · WI DNR · 2025 (PDF)
Lake Details
Max depth
10 ft
Surface area
109 acres
Shoreline
4.1 mi
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Fishing Decatur Lake
EPA Impairment Status
Decatur Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Aquatic life, Recreation.
Source: EPA ATTAINS assessment unit WI10030160 · Official waterbody report
Nearby Lakes in Green County
Frequently asked questions about Decatur Lake
Where is Decatur Lake?
- Decatur Lake is a lake in Green County, Wisconsin. Its water-quality measurements are published by Wisconsin DNR and shown on this page as reported.
What is the water quality of Decatur Lake?
- Decatur Lake in Green County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Maximum depth: 10 ft. Surface area: 109 acres.
Is Decatur Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Decatur Lake is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
How deep is Decatur Lake?
- Decatur Lake has a maximum depth of 10 feet. The lake covers 109 acres.
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Where this data comes from
Measurements for Decatur Lake come from the EPA Water Quality Portal. Per-sample source details are not recorded for this lake.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database