Green Lake
Green Lake in Walworth County, Wisconsin has a water quality grade of B (Good). Water clarity: 11 ft visibility. Phosphorus: 10.7 µg/L. Maximum depth: 57 ft. Surface area: 311 acres.
Wisconsin DNR lists Panfish as common on Green Lake. DNR survey details →
- Clarity
- 11 ft
- Max depth
- 57 ft
- Area
- 311 acres
- Type
- Mesotrophic
- Trend
- ↓ Declining
- Public access
- Yes
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Green Lake is a 311-acre mesotrophic lake in Walworth County, Wisconsin with a maximum depth of 57 feet. Water quality is graded B based on 1 sampling years through 2026. Overall water quality is declining over recent sampling years. The lake supports 4 documented fish species including Panfish, Largemouth Bass, and Northern Pike. Public access is available. Compared to the 18 other monitored lakes in Walworth County, Green Lake ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-06-12. Grade methodology: LakeQuality methodology.
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Swimming Safety
Grade onlyLow algae
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Good for swimming, clear water with low algae levels
Water Quality Grade: B (Good)
Good clarity, visible to about 11 ft. Phosphorus level: 10.7 µg/L. Trophic State Index: 40.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 11 ft | Not graded |
| Phosphorus | 10.7 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 40 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Green Lake
Compare lakeside cabins, hotels, and vacation rentals near Green Lake in Walworth 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 Green Lake
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Planning a whole trip? See where to stay at Wisconsin’s top lakes →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Green Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was high (337,287 cells/mL) on April 11, 2026.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Wisconsin DNR lists Panfish as common on Green Lake.
A DNR fisheries survey reports fish abundance and catch rates, not a water-quality grade. LakeQuality grades Green Lake B from EPA Water Quality Portal chemistry, and the water-quality trend over 7 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
WI DNR Lake Profile
Authoritative data from the Wisconsin DNR LakePages. Monitored by volunteers since 2006. 1 station on file (most recent sample 2025).
Fish Species (DNR-rated)
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 57 ft |
| Surface Area | 311 acres |
| Public Access | Yes |
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Green Lake
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: ↓ Declining
Based on 7 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.277 m/yr | 7 |
| Phosphorus | → Stable | +0.09 µg/L/yr | 7 |
County Ranking
Ranked #4 of 19 lakes in Walworth County
Nearby Lakes in Walworth County
Frequently asked questions about Green Lake
Where is Green Lake?
- Green Lake is a lake in Walworth County, Wisconsin. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Green Lake?
- Green Lake in Walworth County, Wisconsin has a water quality grade of B (Good). Water clarity: 11 ft visibility. Phosphorus: 10.7 µg/L. Maximum depth: 57 ft. Surface area: 311 acres.
Is Green Lake safe to swim in?
- Good for swimming, clear water with low algae levels. Green Lake has a water quality grade of B (Good). Always check local health department advisories before swimming.
How deep is Green Lake?
- Green Lake has a maximum depth of 57 feet. The lake covers 311 acres.
What fish are in Green Lake?
- Fish species found in Green Lake include Panfish, Largemouth Bass, Northern Pike, Walleye. Green Lake is located in Walworth County, Wisconsin.
What did the DNR fisheries survey find at Green Lake?
- Wisconsin DNR lists Panfish as common on Green Lake. A DNR fisheries survey reports fish abundance and catch rates, not a water-quality grade. LakeQuality grades Green Lake B from EPA Water Quality Portal chemistry, and the water-quality trend over 7 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
Does Green Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Green Lake (clouds, ice, or an off-season gap). The most recent reading was high (337,287 cells/mL). Blue-green algae can appear and clear within days, so check Wisconsin's current advisory before swimming.
Explore Green Lake across LakeQuality
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Species activity outlook by water temperature and season
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Moderate nutrients, good water quality
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Other Grade B Lakes in Wisconsin
Mesotrophic Lakes in Wisconsin
Where this data comes from
62 measurements from 1 monitoring station, 2020–2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Wisconsin Department of Natural Resources
WIDNR_WQX62 samples · 2020–2026
Analytical methods
- Phosphorus by Colorimetry
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Lake size & watershed from HydroLAKES (HydroSHEDS)
Fish and recreation data from Wisconsin DNR Lakes