Pewaukee Lake
Pewaukee Lake in Waukesha County, Wisconsin has a water quality grade of B (Good). Water clarity: 7.5 ft visibility. Phosphorus: 19.9 µg/L. Maximum depth: 45 ft. Surface area: 2437 acres.
Wisconsin DNR lists Musky as common on Pewaukee Lake. DNR survey details →
- Clarity
- 7.5 ft
- Typical in August
- 76°F
- Max depth
- 45 ft
- Area
- 2,437 acres
- Type
- Mesotrophic
- Trend
- ↑ Improving
- Public access
- Yes
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Pewaukee Lake is a 2,437-acre mesotrophic lake in Waukesha County, Wisconsin with a maximum depth of 45 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 5 documented fish species including Musky, Panfish, and Largemouth Bass. Public access is available with 1 public boat landing. Compared to the 34 other monitored lakes in Waukesha County, Pewaukee Lake ranks #14 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-05-21. 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 7.5 ft. Phosphorus level: 19.9 µg/L. Trophic State Index: 48.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 7.5 ft | Not graded |
| Phosphorus | 19.9 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 48 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Pewaukee Lake
Compare lakeside cabins, hotels, and vacation rentals near Pewaukee 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.
Top-rated places to stay near Pewaukee Lake
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Planning a whole trip? See where to stay at Wisconsin’s top lakes →
Water Temperature
Pewaukee Lake typically sits around 76°F at the surface in August. Summer average is about 76°F. Usually warmest in Aug (about 76°F) and coldest in Nov (about 40°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 12 field readings (2024–2025) via the EPA Water Quality Portal. See the full Pewaukee Lake water temperature breakdown →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Pewaukee Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was moderate (80,168 cells/mL) on June 27, 2026.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Wisconsin DNR lists Musky as common on Pewaukee Lake.
A DNR fisheries survey reports fish abundance and catch rates, not a water-quality grade. LakeQuality grades Pewaukee 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. 4 stations on file (most recent sample 2025).
Fish Species (DNR-rated)
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 45 ft |
| Surface Area | 2,437 acres |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Pewaukee LakePublic
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 Pewaukee 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 | +1.002 m/yr | 6 |
| Phosphorus | ↑ Improving | -1.11 µg/L/yr | 5 |
Reservoir Info (USACE NID)
Pewaukee Lake is a man-made reservoir impounded by the Pewaukee (completed 1842), built primarily for recreation on the PEWAUKEE; gravity-type dam, 14 ft tall and 800 ft long.
- Surface area
- 2,493 ac
- Normal storage
- 15,000 ac-ft
- Max storage
- 36,900 ac-ft
- Drainage area
- 27.6 sq mi
- Hazard class
- High
- Owner
- Village Of Pewaukee
Source: USACE National Inventory of Dams, NID ID WI00336 · Operator website
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Pewaukee Lake under Clean Water Act (NPDES) discharge permits, including 1 classified by the EPA as major discharger. 1 facility has a reported Clean Water Act violation in the past three years.
- Sussex Wastewater Treatment FacilitySussex · 4.5 mi away · NPDES WI0020559MajorRecent 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.
County Ranking
Ranked #14 of 35 lakes in Waukesha County
Nearby Lakes in Waukesha County
Frequently asked questions about Pewaukee Lake
Where is Pewaukee Lake?
- Pewaukee 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 Pewaukee Lake?
- Pewaukee Lake in Waukesha County, Wisconsin has a water quality grade of B (Good). Water clarity: 7.5 ft visibility. Phosphorus: 19.9 µg/L. Maximum depth: 45 ft. Surface area: 2437 acres.
Is Pewaukee Lake safe to swim in?
- Good for swimming, clear water with low algae levels. Pewaukee Lake has a water quality grade of B (Good). Always check local health department advisories before swimming.
What is the water temperature of Pewaukee Lake?
- Pewaukee Lake typically sits around 76°F at the surface in August, from 12 EPA Water Quality Portal field readings (2024–2025). That is a typical value for the month, not a live reading.
How deep is Pewaukee Lake?
- Pewaukee Lake has a maximum depth of 45 feet. The lake covers 2437 acres.
What fish are in Pewaukee Lake?
- Fish species found in Pewaukee Lake include Musky, Panfish, Largemouth Bass, Northern Pike, Walleye. Pewaukee Lake is located in Waukesha County, Wisconsin.
What did the DNR fisheries survey find at Pewaukee Lake?
- Wisconsin DNR lists Musky as common on Pewaukee Lake. A DNR fisheries survey reports fish abundance and catch rates, not a water-quality grade. LakeQuality grades Pewaukee 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.
Does Pewaukee Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Pewaukee Lake (clouds, ice, or an off-season gap). The most recent reading was moderate (80,168 cells/mL). Blue-green algae can appear and clear within days, so check Wisconsin's current advisory before swimming.
Are there boat ramps on Pewaukee Lake?
- Pewaukee Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Pewaukee Lake. Public access is listed as yes.
Explore Pewaukee Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
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Fish species and best lakes in Waukesha County
Species activity outlook by water temperature and season
Where to stay at Wisconsin's top lakes, each with its grade
Moderate nutrients, good water quality
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Compare Pewaukee Lake With Nearby Lakes
Where this data comes from
104 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_WQX104 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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
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