Upper Nemahbin Lake
Upper Nemahbin Lake in Waukesha County, Wisconsin has a water quality grade of B (Good). Water clarity: 12 ft visibility. Phosphorus: 13.7 µg/L. Maximum depth: 60 ft. Surface area: 277 acres.
Wisconsin DNR lists Panfish as common on Upper Nemahbin Lake. DNR survey details →
- Clarity
- 12 ft
- Typical in August
- 74°F
- Max depth
- 60 ft
- Area
- 277 acres
- Type
- Mesotrophic
- Trend
- ↑ Improving
- Public access
- Yes
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Upper Nemahbin Lake is a 277-acre mesotrophic lake in Waukesha County, Wisconsin with a maximum depth of 60 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 Panfish, Largemouth Bass, and Smallmouth Bass. Public access is available with 1 public boat landing. Compared to the 34 other monitored lakes in Waukesha County, Upper Nemahbin Lake ranks #28 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-06-26. 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 12 ft. Phosphorus level: 13.7 µg/L. Trophic State Index: 42.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 12 ft | Not graded |
| Phosphorus | 13.7 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 42 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Upper Nemahbin Lake
Compare lakeside cabins, hotels, and vacation rentals near Upper Nemahbin 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 Upper Nemahbin Lake
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Planning a whole trip? See where to stay at Wisconsin’s top lakes →
Water Temperature
Upper Nemahbin Lake typically sits around 74°F at the surface in August. Summer average is about 77°F. Usually warmest in Jul (about 79°F) and coldest in Aug (about 74°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 8 field readings (2024–2025) via the EPA Water Quality Portal. See the full Upper Nemahbin Lake water temperature breakdown →
Wisconsin DNR lists Panfish as common on Upper Nemahbin Lake.
A DNR fisheries survey reports fish abundance and catch rates, not a water-quality grade. LakeQuality grades Upper Nemahbin Lake B from EPA Water Quality Portal chemistry, and the water-quality trend over 7 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. Monitored by volunteers since 1986. 4 stations on file (most recent sample 2025).
Fish Species (DNR-rated)
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 60 ft |
| Surface Area | 277 acres |
| Public Access | Yes |
Recreation & Access
- Nemahbin LakesPublic
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 Upper Nemahbin 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 7 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.464 m/yr | 7 |
| Phosphorus | ↑ Improving | -0.54 µg/L/yr | 7 |
County Ranking
Ranked #28 of 35 lakes in Waukesha County
Nearby Lakes in Waukesha County
Frequently asked questions about Upper Nemahbin Lake
Where is Upper Nemahbin Lake?
- Upper Nemahbin 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 Upper Nemahbin Lake?
- Upper Nemahbin Lake in Waukesha County, Wisconsin has a water quality grade of B (Good). Water clarity: 12 ft visibility. Phosphorus: 13.7 µg/L. Maximum depth: 60 ft. Surface area: 277 acres.
Is Upper Nemahbin Lake safe to swim in?
- Good for swimming, clear water with low algae levels. Upper Nemahbin Lake has a water quality grade of B (Good). Always check local health department advisories before swimming.
What is the water temperature of Upper Nemahbin Lake?
- Upper Nemahbin Lake typically sits around 74°F at the surface in August, from 8 EPA Water Quality Portal field readings (2024–2025). That is a typical value for the month, not a live reading.
How deep is Upper Nemahbin Lake?
- Upper Nemahbin Lake has a maximum depth of 60 feet. The lake covers 277 acres.
What fish are in Upper Nemahbin Lake?
- Fish species found in Upper Nemahbin Lake include Panfish, Largemouth Bass, Smallmouth Bass, Northern Pike, Walleye. Upper Nemahbin Lake is located in Waukesha County, Wisconsin.
What did the DNR fisheries survey find at Upper Nemahbin Lake?
- Wisconsin DNR lists Panfish as common on Upper Nemahbin Lake. A DNR fisheries survey reports fish abundance and catch rates, not a water-quality grade. LakeQuality grades Upper Nemahbin Lake B from EPA Water Quality Portal chemistry, and the water-quality trend over 7 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.
Are there boat ramps on Upper Nemahbin Lake?
- Upper Nemahbin Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Nemahbin Lakes. Public access is listed as yes.
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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
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