Harpt Lake
Manitowoc County, Wisconsin32 acresView mapDirections
Wisconsin DNR publishes the water-quality measurements for Harpt Lake. Here is what has been measured.
- Eutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- Curly-Leaf Pondweed
- 54 ft max depth
- Public access
Harpt Lake in Manitowoc County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 3.5 ft visibility. Phosphorus: 45.3 µg/L. Maximum depth: 54 ft. Surface area: 32 acres.
Wisconsin DNR rates Panfish as abundant on Harpt Lake. DNR survey details →
Harpt Lake is a 32-acre productive, nutrient-rich eutrophic lake in Manitowoc County, Wisconsin with a maximum depth of 54 feet. Overall water quality is declining over recent sampling years. The lake supports 4 documented fish species including Panfish, Largemouth Bass, and Northern Pike. Public access is available with 1 public boat landing. Compared to the 15 other monitored lakes in Manitowoc County, Harpt Lake ranks #11 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-06-15. Methodology: how these readings are compared.
Harpt Lake covers about 32 acres in Manitowoc County. It has one public boat landing. Vrbo is where to look for cabins and lake homes around Harpt Lake, and Booking.com and Expedia search hotels near the lake for your dates.
What Harpt Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
- Fishing4 species recorded
- Deep water54 ft surveyed max depth
Swimming conditions
Readings onlyRecreation use not supported
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. Harpt Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Harpt 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 Harpt Lake
These are the measurements Wisconsin DNR publishes for Harpt Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Murky, only visible to about 3.5 ft. Phosphorus 45.3 µg/L. TSI 59.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 3.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 45.3µg/L | Fair 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. | 59 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Harpt Lake
Answers come straight from the public measurements and survey records on this page.
Wisconsin DNR rates Panfish as abundant on Harpt Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Harpt Lake’s water-quality measurements separately, and the water-quality trend over 7 years of monitoring is declining. 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 2003. 2 stations on file (most recent sample 2025).
Fish Species (DNR-rated)
Lake Details
Max depth
54 ft
Surface area
32 acres
Public access
Yes
Listed by Wisconsin DNR
Recreation & Access
- Harpt LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Harpt Lake
Compare lakeside cabins, hotels, and vacation rentals near Harpt Lake in Manitowoc 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 Harpt Lake
Prices for Oct 9–11, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Wisconsin’s top lakes →
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Fish Species
Click a species to see every lake where it is documented.
Fishing Harpt 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: Worsening
Based on 7 years of monitoring (2020–2026).
Water clarity
Worsening6 years
Phosphorus
Worsening+12.56 µg/L/yr7 years
EPA Impairment Status
Harpt Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Aquatic life, Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit WI10000321 · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Harpt Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Denmark Wastewater Treatment FDenmark · 4.2 mi away · NPDES WI0021741Recent 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.
Nearby Lakes in Manitowoc County
Frequently asked questions about Harpt Lake
Where is Harpt Lake?
- Harpt Lake is a lake in Manitowoc County, Wisconsin. Its water-quality measurements are published by Wisconsin DNR and shown on this page as reported.
What is the water quality of Harpt Lake?
- Harpt Lake in Manitowoc County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 3.5 ft visibility. Phosphorus: 45.3 µg/L. Maximum depth: 54 ft. Surface area: 32 acres.
Is Harpt Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Harpt Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
How deep is Harpt Lake?
- Harpt Lake has a maximum depth of 54 feet. The lake covers 32 acres.
What fish are in Harpt Lake?
- Fish species found in Harpt Lake include Panfish, Largemouth Bass, Northern Pike, Walleye. Harpt Lake is located in Manitowoc County, Wisconsin.
What did the DNR fisheries survey find at Harpt Lake?
- Wisconsin DNR rates Panfish as abundant on Harpt Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Harpt Lake’s water-quality measurements separately, and the water-quality trend over 7 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
Are there boat ramps on Harpt Lake?
- Harpt Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Harpt Lake. Public access is listed as yes.
Can I fish at Harpt Lake?
- Harpt Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. 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 Harpt Lake across LakeQuality
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Where this data comes from
50 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_WQX50 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
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Fish and recreation data from Wisconsin DNR Lakes
Named boat-access points from the USGS National Boat Ramps inventory