Lower Nemahbin Lake
Waukesha County, Wisconsin239 acresView mapDirections
Wisconsin DNR publishes the water-quality measurements for Lower Nemahbin Lake. Here is what has been measured.
- Mesotrophic
- 3 aquatic invasives
- 36 ft max depth
- Public access
Lower Nemahbin Lake in Waukesha County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 10.9 ft visibility. Phosphorus: 10.9 µg/L. Maximum depth: 36 ft. Surface area: 239 acres.
Lower Nemahbin Lake is a 239-acre mesotrophic lake in Waukesha County, Wisconsin with a maximum depth of 36 feet. 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. Compared to the 34 other monitored lakes in Waukesha County, Lower Nemahbin Lake ranks #24 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-06-07. Methodology: how these readings are compared.
Lower Nemahbin Lake covers about 240 acres in Waukesha County. Vrbo is where to look for cabins and lake homes around Lower Nemahbin Lake, and Booking.com and Expedia search hotels near the lake for your dates.
What Lower Nemahbin Lake is good for
From access and monitoring records, not editorial picks.
- Clear water10.9 ft of visibility
- Fishing5 species recorded
- Deep water36 ft surveyed max depth
Swimming conditions
Readings onlyLow algae
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. Check local advisories before you swim.
Whether Lower Nemahbin 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 Lower Nemahbin Lake
These are the measurements Wisconsin DNR publishes for Lower Nemahbin 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 10.9 ft. Phosphorus 10.9 µg/L. TSI 41.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 10.9ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 10.9µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 41 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Lower Nemahbin Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Lower Nemahbin Lake typically sits around 77°F at the surface in August. Summer average is about 78°F. Usually warmest in Jun (about 78°F) and coldest in Apr (about 54°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (54°F) to its warmest (78°F).
Typical surface water temperature by month, from 9 field readings (2024–2025) via the EPA Water Quality Portal. See the full Lower Nemahbin Lake water temperature breakdown →
Lake Details
Max depth
36 ft
Surface area
239 acres
Public access
Yes
Listed by Wisconsin DNR
Lake Size & Watershed
Watershed (drainage) area
146 sq mi
HydroLAKES / HydroSHEDS
Shoreline
3.7 mi
HydroLAKES / HydroSHEDS
Elevation
869 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Stays via Stay22
Stays near Lower Nemahbin Lake
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Follow Lower Nemahbin Lake’s readings
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Fish Species
Click a species to see every lake where it is documented.
Fishing Lower 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 (2020–2026).
Water clarity
Improving7 years
Phosphorus
Improving-0.5 µg/L/yr7 years
Reservoir Info (USACE NID)
Lower Nemahbin Lake is a man-made reservoir impounded by the Lower Lake Nemahbin (completed 1934), built primarily for recreation on the BARK; gravity-type dam, 8 ft tall and 200 ft long.
- Surface area
- 268 ac
- Normal storage
- 270 ac-ft
- Max storage
- 1,880 ac-ft
- Drainage area
- 54 sq mi
- Hazard class
- Low
- Owner
- Village Of Summit
Source: USACE National Inventory of Dams, NID ID WI01120 · Operator website
Nearby Lakes in Waukesha County
Frequently asked questions about Lower Nemahbin Lake
Where is Lower Nemahbin Lake?
- Lower Nemahbin Lake is a lake in Waukesha County, Wisconsin. Its water-quality measurements are published by Wisconsin DNR and shown on this page as reported.
What is the water quality of Lower Nemahbin Lake?
- Lower Nemahbin Lake in Waukesha County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 10.9 ft visibility. Phosphorus: 10.9 µg/L. Maximum depth: 36 ft. Surface area: 239 acres.
Is Lower Nemahbin Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Lower Nemahbin Lake?
- Lower Nemahbin Lake typically sits around 77°F at the surface in August, from 9 EPA Water Quality Portal field readings (2024–2025). That is a typical value for the month, not a live reading.
How deep is Lower Nemahbin Lake?
- Lower Nemahbin Lake has a maximum depth of 36 feet. The lake covers 239 acres.
What fish are in Lower Nemahbin Lake?
- Fish species found in Lower Nemahbin Lake include Panfish, Largemouth Bass, Smallmouth Bass, Northern Pike, Walleye. Lower Nemahbin Lake is located in Waukesha County, Wisconsin.
Can I fish at Lower Nemahbin Lake?
- Public access to Lower Nemahbin 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 Lower Nemahbin Lake across LakeQuality
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Species activity outlook by water temperature and season
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Where this data comes from
125 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_WQX125 samples · 2020–2026
Analytical methods
- Phosphorus by Colorimetry
Monitoring station identifiers (1)
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Fish and recreation data from Wisconsin DNR Lakes