Carp Lake
Carp Lake in Unknown County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 8.5 ft visibility. Maximum depth: 34 ft. Surface area: 836.35 acres.
Minnesota DNR surveys at Carp Lake average 7.49 walleye per unit of sampling effort (CPUE) across 9 surveys. The most recent is a Standard Survey dated September 5, 2017. Length samples in the latest survey that recorded them ran 8–26 inches. DNR survey details →
- Clarity
- 8.5 ft
- Max depth
- 34 ft
- Area
- 836 acres
- Trend
- → Stable
- Public access
- No
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Why Carp Lake has no grade
We grade a lake only when the monitoring record supports a letter: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Carp Lake, no EPA ecoregion for this lake, so the National Lakes Assessment condition thresholds cannot be applied. Sampling here has recorded water clarity, but not phosphorus and algae (chlorophyll-a).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by MPCA and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Carp Lake is a 836-acre lake in Unknown County, Minnesota with a maximum depth of 34 feet. The lake supports 10 documented fish species including bluegill, cisco species, and largemouth bass. No public access — the lake is private or restricted.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-07-26. Grade methodology: LakeQuality methodology.
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Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Carp Lake
These readings exist but are not enough for an A–F grade — see why.
Moderate clarity, visible to about 8.5 ft. Trophic State Index: 46.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 8.5 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 46 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Carp Lake
Compare lakeside cabins, hotels, and vacation rentals near Carp Lake in Unknown County, Minnesota — 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 Carp Lake
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Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Carp Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was high (387,258 cells/mL) on November 29, 2025.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Minnesota DNR surveys at Carp Lake average 7.49 walleye per unit of sampling effort (CPUE) across 9 surveys. The most recent is a Standard Survey dated September 5, 2017. Length samples in the latest survey that recorded them ran 8–26 inches.
A DNR fisheries survey reports fish abundance and catch rates, not a water-quality grade. LakeQuality does not assign an A–F grade on Carp Lake — official chemistry is on file, not a letter, and the water-quality trend over 5 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
9 surveys on file from MN DNR Fisheries. Most recent: 2017-09-05 (Standard Survey).
Top Species by Catch Rate
| Species | Avg catch rate (CPUE) | Avg Weight |
|---|---|---|
| Walleye | 7.49 | 1.61 lb |
| Tullibee (Cisco) | 6.15 | 0.64 lb |
| White Sucker | 4.19 | 2.8 lb |
| Bluegill | 2.35 | 0.19 lb |
| Northern Pike | 2.28 | 3.61 lb |
CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE means more abundant in standardized sampling. This is not a weekly bite report.
Length Distributions
Number of fish caught at each inch class in the most recent survey that recorded lengths. Red dashed line marks an approximate trophy threshold for that species.
Walleye
Tullibee (Cisco)
White Sucker
Bluegill
From the 2017-09-05 survey
Birch Lake is located approximately 18 miles NE of Ely within the BWCAW. The northern half of the lake is part of Ontario's Quetico Provincial Park. Birch Lake is 836 acres with 397 of these acres in Minnesota. Visitors should be familiar with appropriate regulations when traveling these wilderness areas. Birch Lake…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Carp Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — BirchFisheries Lake Survey · MN DNR LakeFinder
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 34 ft |
| Surface Area | 836 acres |
| Shoreline Length | 27.8 mi |
| Littoral Zone | 41% |
| Public Access | No |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Carp Lake
Water Quality Trend: → Stable
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.049 m/yr | 5 |
EPA Impairment Status
Carp 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 MN38-0491-00 · Official waterbody report · Matched by proximity (2.62 km)
Nearby Lakes in Unknown County
Frequently asked questions about Carp Lake
Where is Carp Lake?
- Carp Lake is a lake in Unknown County, Minnesota. LakeQuality has not rated this lake (UNRATED) — there is not enough recent sampling to assign a letter.
What is the water quality grade for Carp Lake?
- Carp Lake in Unknown County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 8.5 ft visibility. Maximum depth: 34 ft. Surface area: 836.35 acres.
Is Carp Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Carp Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
How deep is Carp Lake?
- Carp Lake has a maximum depth of 34 feet. The lake covers 836.35 acres.
What fish are in Carp Lake?
- Fish species found in Carp Lake include bluegill, cisco species, largemouth bass, northern pike, pumpkinseed, rock bass, smallmouth bass, walleye, white sucker, yellow perch. Carp Lake is located in Unknown County, Minnesota.
What did the DNR fisheries survey find at Carp Lake?
- Minnesota DNR surveys at Carp Lake average 7.49 walleye per unit of sampling effort (CPUE) across 9 surveys. The most recent is a Standard Survey dated September 5, 2017. Length samples in the latest survey that recorded them ran 8–26 inches. A DNR fisheries survey reports fish abundance and catch rates, not a water-quality grade. LakeQuality does not assign an A–F grade on Carp Lake — official chemistry is on file, not a letter, and the water-quality trend over 5 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
Does Carp Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Carp Lake (clouds, ice, or an off-season gap). The most recent reading was high (387,258 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Explore Carp Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
Fish species and top-graded lakes across Minnesota
Fish species and best lakes in Unknown County
Species activity outlook by water temperature and season
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Minnesota's cleanest and most-polluted lakes, ranked
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Where this data comes from
23 measurements from 8 monitoring stations, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA23 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
Monitoring station identifiers (8)
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder