Decatur Lake
Decatur Lake in Green County, Wisconsin is not rated for water quality — its monitoring record does not meet the evidence bar. Surface area: 109 acres.
- Area
- 109 acres
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Why Decatur Lake has no grade
We grade a lake only when the monitoring record supports a letter: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Decatur Lake, no water-quality sampling on record for this lake.
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by WI DNR and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Decatur Lake is a 109-acre lake in Green County, Wisconsin.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled recent years. Grade methodology: LakeQuality methodology.
Watch Decatur Lake water quality
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Swimming Safety
Not ratedElevated nutrients
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Decatur Lake
These readings exist but are not enough for an A–F grade — see why.
No clarity data. Trophic State Index: undefined.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) |
Where to stay near Decatur Lake
Compare lakeside cabins, hotels, and vacation rentals near Decatur Lake in Green County, Wisconsin — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Decatur Lake
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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
| Characteristic | Value |
|---|---|
| Surface Area | 109 acres |
No bathymetric survey has been published for Decatur Lake, so its depth is not documented here.
Fishing Decatur Lake
Nearby Lakes in Green County
Frequently asked questions about Decatur Lake
Where is Decatur Lake?
- Decatur Lake is a lake in Green County, Wisconsin. LakeQuality has not rated this lake (UNRATED) — no water-quality sampling on record for this lake.
What is the water quality grade for Decatur Lake?
- Decatur Lake in Green County, Wisconsin is not rated for water quality — its monitoring record does not meet the evidence bar. Surface area: 109 acres.
Is Decatur Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Decatur Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
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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.