Lake Keesus
Lake Keesus in Waukesha County, Wisconsin has a water quality grade of B (Good). Water clarity: 9.2 ft visibility. Phosphorus: 15.8 µg/L. Maximum depth: 42 ft. Surface area: 235 acres.
Wisconsin DNR rates Largemouth Bass as abundant on Lake Keesus. DNR survey details →
- Clarity
- 9.2 ft
- Max depth
- 42 ft
- Area
- 235 acres
- Type
- Mesotrophic
- Trend
- ↑ Improving
- Public access
- Yes
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Lake Keesus is a 235-acre mesotrophic lake in Waukesha County, Wisconsin with a maximum depth of 42 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, Lake Keesus ranks #17 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-04-14. 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 9.2 ft. Phosphorus level: 15.8 µg/L. Trophic State Index: 45.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 9.2 ft | Not graded |
| Phosphorus | 15.8 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 45 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Lake Keesus
Compare lakeside cabins, hotels, and vacation rentals near Lake Keesus 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 Lake Keesus
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Planning a whole trip? See where to stay at Wisconsin’s top lakes →
Wisconsin DNR rates Largemouth Bass as abundant on Lake Keesus.
A DNR fisheries survey reports fish abundance and catch rates, not a water-quality grade. LakeQuality grades Lake Keesus 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 2026).
Fish Species (DNR-rated)
DNR Reports & Resources
Wisconsin DNR Fisheries scientists publish multi-year survey reports for Lake Keesus 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).
- 2023Lake Keesus spring shocking survey, 2023Spring Shocking Survey · WI DNR · 2023 (PDF)
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 42 ft |
| Surface Area | 235 acres |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Merton MillpondPublic
- Lake KeesusPublic
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 Lake Keesus
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 | +1.474 m/yr | 6 |
| Phosphorus | ↑ Improving | -1.06 µg/L/yr | 6 |
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Lake Keesus under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Essential Industries IncMerton · 1.4 mi away · NPDES WI0066648Recent 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 #17 of 35 lakes in Waukesha County
Nearby Lakes in Waukesha County
Frequently asked questions about Lake Keesus
Where is Lake Keesus?
- Lake Keesus 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 Lake Keesus?
- Lake Keesus in Waukesha County, Wisconsin has a water quality grade of B (Good). Water clarity: 9.2 ft visibility. Phosphorus: 15.8 µg/L. Maximum depth: 42 ft. Surface area: 235 acres.
Is Lake Keesus safe to swim in?
- Good for swimming, clear water with low algae levels. Lake Keesus has a water quality grade of B (Good). Always check local health department advisories before swimming.
How deep is Lake Keesus?
- Lake Keesus has a maximum depth of 42 feet. The lake covers 235 acres.
What fish are in Lake Keesus?
- Fish species found in Lake Keesus include Panfish, Largemouth Bass, Northern Pike, Walleye. Lake Keesus is located in Waukesha County, Wisconsin.
What did the DNR fisheries survey find at Lake Keesus?
- Wisconsin DNR rates Largemouth Bass as abundant on Lake Keesus. A DNR fisheries survey reports fish abundance and catch rates, not a water-quality grade. LakeQuality grades Lake Keesus 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 Lake Keesus?
- Lake Keesus has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Merton Millpond, Lake Keesus. Public access is listed as yes.
Explore Lake Keesus across LakeQuality
Depth, room, public access, and the state wake-sport rules
Fish species and top-graded lakes across Wisconsin
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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State Parks Near Lake Keesus
Other Grade B Lakes in Wisconsin
Mesotrophic Lakes in Wisconsin
Where this data comes from
48 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_WQX48 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
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