Green Lake
Green Lake County, Wisconsin7,920 acresView mapDirections
Wisconsin DNR publishes the water-quality measurements for Green Lake. Here is what has been measured.
- Mesotrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- 4 aquatic invasives
- 236 ft max depth
- Public access
Green Lake in Green Lake County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 13.5 ft visibility. Phosphorus: 38.1 µg/L. Chlorophyll-a (algae): 4.4 µg/L. Maximum depth: 236 ft. Surface area: 7920 acres.
Wisconsin DNR lists Smallmouth Bass as common on Green Lake. DNR survey details →
Green Lake is a 7,920-acre mesotrophic lake in Green Lake County, Wisconsin with a maximum depth of 236 feet. Overall water quality is improving over recent sampling years. The lake supports 7 documented fish species including Panfish, Largemouth Bass, and Smallmouth Bass. Public access is available with 3 public beaches. Compared to the 6 other monitored lakes in Green Lake County, Green Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-06-10. Methodology: how these readings are compared.
At about 7,900 acres, Green Lake is large enough that where you stay decides which shore you see most of. If you are planning to stay, you can search lake houses and cabins around Green Lake on Vrbo, or look for a hotel room near the lake on Booking.com or Expedia.
What Green Lake is good for
From access and monitoring records, not editorial picks.
- Clear water13.5 ft of visibility
- Beach3 documented beaches
- Fishing7 species recorded
- Deep water236 ft surveyed max depth
- Big water7,920 acres
Green Lake Water Quality Summary (2026)
A printable one-page summary for Green Lake: clarity, phosphorus, algae, multi-year trend, depth, and fish — with sources.
Swimming conditions
Readings onlyRecreation use not supported
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Green Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Green 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 Green Lake
These are the measurements Wisconsin DNR publishes for Green Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Good clarity, visible to about 13.5 ft. Phosphorus 38.1 µg/L. Chlorophyll-a 4.4 µg/L. TSI 47.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 13.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 38.1µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 4.4µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 47 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Green Lake
Answers come straight from the public measurements and survey records on this page.
Current Conditions
USGS snapshot Jul 6, 2026, 5:00 AM from gauge 434840089000001 (Green Lake at Green Lake, WI). Station page ↗ — a live reading replaces this snapshot when the gauge responds. Missing live data is not an all-clear.
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 (376,704 cells/mL) on September 16, 2025.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Wisconsin DNR lists Smallmouth Bass as common on Green Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Green Lake’s water-quality measurements separately, and the water-quality trend over 3 years of monitoring is improving. 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. 85 stations on file (most recent sample 2026).
Fish Species (DNR-rated)
DNR Reports & Resources
Wisconsin DNR Fisheries scientists publish multi-year survey reports for Green Lake covering fish populations, stocking, water quality, and management. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- 2024Little Green Lake comprehensive survey, 2024Comprehensive Survey · WI DNR · 2024 (PDF)
- 2023Big Green Lake creel survey, 2023Creel Survey · WI DNR · 2023 (PDF)
- 2022Big Green Lake comprehensive survey, 2022Comprehensive Survey · WI DNR · 2022 (PDF)
Lake Details
Max depth
236 ft
Surface area
7,920 acres
Public access
Yes
Listed by Wisconsin DNR
Recreation & Access
Stays via Stay22
Stays near Green Lake
Compare lakeside cabins, hotels, and vacation rentals near Green Lake in Green Lake 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 trip? Cabins and lodging at Green Lake → · more Wisconsin lake trips
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Fish Species
Click a species to see every 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 readings over time
3 seasons of samples on record (2023–2025). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Improving3 years
EPA Impairment Status
Green Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Aquatic life, Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit WI10000969 · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Green Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Green Lake Sanitary DistrictGreen Lake · 2.2 mi away · NPDES WI0036846Recent violation
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
Nearby Lakes in Green Lake County
Frequently asked questions about Green Lake
Where is Green Lake?
- Green Lake is a lake in Green Lake County, Wisconsin. Its water-quality measurements are published by Wisconsin DNR and shown on this page as reported.
What is the water quality of Green Lake?
- Green Lake in Green Lake County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 13.5 ft visibility. Phosphorus: 38.1 µg/L. Chlorophyll-a (algae): 4.4 µg/L. Maximum depth: 236 ft. Surface area: 7920 acres.
Is Green Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Green Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
How deep is Green Lake?
- Green Lake has a maximum depth of 236 feet. The lake covers 7920 acres.
What fish are in Green Lake?
- Fish species found in Green Lake include Panfish, Largemouth Bass, Smallmouth Bass, Northern Pike, Trout, Walleye, Catfish. Green Lake is located in Green Lake County, Wisconsin.
What did the DNR fisheries survey find at Green Lake?
- Wisconsin DNR lists Smallmouth Bass as common on Green Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Green Lake’s water-quality measurements separately, and the water-quality trend over 3 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.
What is the water level at Green Lake?
- The USGS snapshot on this page for Green Lake is 6.68 ft of gage height, recorded Jul 6, 2026, 5:00 AM at gauge 434840089000001. Current Conditions hydrates a live NWIS reading from that same station when the gauge responds. A missed live fetch is not an all-clear.
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 (376,704 cells/mL). Blue-green algae can appear and clear within days, so check Wisconsin's current advisory before swimming.
Can I fish at Green Lake?
- Public access to Green Lake is listed as yes on the lake record. Seasons, size and bag limits, and whether you need a license are set by Wisconsin's fish and wildlife agency, so check its current regulations before you go.
Explore Green Lake across LakeQuality
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Where this data comes from
520 measurements from 8 monitoring stations, 2020–2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- USGS Wisconsin Water Science Center
USGS-WI298 samples · 2020–2023 - Wisconsin Department of Natural Resources
WIDNR_WQX222 samples · 2023–2026
Analytical methods
- Phosphorus by Colorimetry
- Turbidity in Water
Monitoring station identifiers (8)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Fish and recreation data from Wisconsin DNR Lakes