Harpt Lake
Harpt Lake in Manitowoc County, Wisconsin has a water quality grade of C (Fair). Water clarity: 3.5 ft visibility. Phosphorus: 45.3 µg/L. Maximum depth: 54 ft. Surface area: 32 acres.
- Clarity
- 3.5 ft
- Max depth
- 54 ft
- Area
- 32 acres
- Type
- Eutrophic
- Trend
- ↓ Declining
- Public access
- Yes
Next lake in Manitowoc County
Harpt Lake is a 32-acre productive, nutrient-rich eutrophic lake in Manitowoc County, Wisconsin with a maximum depth of 54 feet. Water quality is graded C based on 1 sampling years through 2026. 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. Grade methodology: LakeGrade methodology.
Watch Harpt Lake water quality
Subscribe for LakeQuality updates by email. No spam, unsubscribe anytime.
Swimming Safety
Grade onlyModerate
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.
Generally safe for swimming, moderate water quality
Water Quality Grade: C (Fair)
Murky, only visible to about 3.5 ft. Phosphorus level: 45.3 µg/L. Trophic State Index: 59.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.5 ft | Not graded |
| Phosphorus | 45.3 µg/L | Fair |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 59 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay 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
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 →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 54 ft |
| Surface Area | 32 acres |
| Public Access | Yes |
Recreation & Access
- Harpt LakePublic
Fish Species
Click a species to see every graded 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.
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)
Water Quality Trend: ↓ Declining
Based on 7 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.3 m/yr | 6 |
| Phosphorus | ↓ Declining | +12.56 µg/L/yr | 7 |
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
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.
County Ranking
Ranked #11 of 16 lakes in Manitowoc County
Nearby Lakes With Higher Grades
Harpt Lake holds Grade C. 2 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Manitowoc County
Frequently asked questions about Harpt Lake
What is the water quality grade for Harpt Lake?
- Harpt Lake in Manitowoc County, Wisconsin has a water quality grade of C (Fair). 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?
- Generally safe for swimming, moderate water quality. Harpt Lake has a water quality grade of C (Fair). Always check local health department advisories before swimming.
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.
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.
Explore Harpt Lake across LakeGrade
Fish species and top-graded lakes across Wisconsin
Fish species and best lakes in Manitowoc County
Species activity outlook by water temperature and season
Where to stay at Wisconsin's top lakes, each with its grade
Lakes in the Sheboygan-Manitowoc, ranked by water quality
High nutrients, frequent algae, reduced clarity
Wisconsin's cleanest and most-polluted lakes, ranked
More Wisconsin Lake Rankings
State Parks Near Harpt Lake
Other Grade C Lakes in Wisconsin
Eutrophic Lakes in Wisconsin
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)
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
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