Denoon Lake
Denoon Lake in Waukesha County, Wisconsin has a water quality grade of B (Good). Water clarity: 9 ft visibility. Phosphorus: 24.7 µg/L. Maximum depth: 55 ft. Surface area: 167 acres.
Wisconsin DNR lists Largemouth Bass as common on Denoon Lake. DNR survey details →
- Clarity
- 9 ft
- Max depth
- 55 ft
- Area
- 167 acres
- Type
- Mesotrophic
- Trend
- ↑ Improving
- Public access
- Yes
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Denoon Lake is a 167-acre mesotrophic lake in Waukesha County, Wisconsin with a maximum depth of 55 feet. Water quality is graded B based on 1 sampling years through 2026. Overall water quality is improving over recent sampling years. The lake supports 4 documented fish species including Panfish, Largemouth Bass, and Northern Pike. Public access is available with 2 public boat landings. Compared to the 34 other monitored lakes in Waukesha County, Denoon Lake ranks #25 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-06-15. 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)
Moderate clarity, visible to about 9 ft. Phosphorus level: 24.7 µg/L. Trophic State Index: 48.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 9 ft | Not graded |
| Phosphorus | 24.7 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 48 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Denoon Lake
Compare lakeside cabins, hotels, and vacation rentals near Denoon Lake in Waukesha 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.
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Wisconsin DNR lists Largemouth Bass as common on Denoon Lake.
A DNR fisheries survey reports fish abundance and catch rates, not a water-quality grade. LakeQuality grades Denoon Lake B from EPA Water Quality Portal chemistry, and the water-quality trend over 6 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. 3 stations on file (most recent sample 2024).
Fish Species (DNR-rated)
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 55 ft |
| Surface Area | 167 acres |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Long LakePublic
- Denoon ParkPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Denoon 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: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +3.375 m/yr | 3 |
| Phosphorus | ↑ Improving | -1.78 µg/L/yr | 6 |
County Ranking
Ranked #25 of 35 lakes in Waukesha County
Nearby Lakes in Waukesha County
Frequently asked questions about Denoon Lake
Where is Denoon Lake?
- Denoon Lake is a lake in Waukesha County, Wisconsin. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Denoon Lake?
- Denoon Lake in Waukesha County, Wisconsin has a water quality grade of B (Good). Water clarity: 9 ft visibility. Phosphorus: 24.7 µg/L. Maximum depth: 55 ft. Surface area: 167 acres.
Is Denoon Lake safe to swim in?
- Good for swimming, clear water with low algae levels. Denoon Lake has a water quality grade of B (Good). Always check local health department advisories before swimming.
How deep is Denoon Lake?
- Denoon Lake has a maximum depth of 55 feet. The lake covers 167 acres.
What fish are in Denoon Lake?
- Fish species found in Denoon Lake include Panfish, Largemouth Bass, Northern Pike, Walleye. Denoon Lake is located in Waukesha County, Wisconsin.
What did the DNR fisheries survey find at Denoon Lake?
- Wisconsin DNR lists Largemouth Bass as common on Denoon Lake. A DNR fisheries survey reports fish abundance and catch rates, not a water-quality grade. LakeQuality grades Denoon Lake B from EPA Water Quality Portal chemistry, and the water-quality trend over 6 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.
Are there boat ramps on Denoon Lake?
- Denoon Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Long Lake, Denoon Park. Public access is listed as yes.
Explore Denoon 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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State Parks Near Denoon Lake
Other Grade B Lakes in Wisconsin
Mesotrophic Lakes in Wisconsin
Where this data comes from
45 measurements from 2 monitoring stations, 2020–2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Wisconsin Department of Natural Resources
WIDNR_WQX45 samples · 2020–2026
Analytical methods
- Phosphorus by Colorimetry
Monitoring station identifiers (2)
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
Named boat-access points from the USGS National Boat Ramps inventory