Big Carnelian Lake
Big Carnelian Lake in Washington County, Minnesota has a water quality grade of A (Excellent). Water clarity: 14.5 ft visibility. Phosphorus: 12 µg/L. Chlorophyll-a (algae): 3.4 µg/L. Maximum depth: 66 ft. Surface area: 457.03 acres.
- Clarity
- 14.5 ft
- Typical in August
- 77°F
- Max depth
- 66 ft
- Area
- 457 acres
- Type
- Mesotrophic
- Trend
- → Stable
- Public access
- Yes
- Ice-out
- Apr 9
- Open water
- 242 days
Next lake in Washington County
Big Carnelian Lake is a 457-acre mesotrophic lake in Washington County, Minnesota with a maximum depth of 66 feet (26-foot average). Water quality is graded A based on 2 sampling years through 2025. The lake supports 12 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 1 public boat landing. Compared to the 74 other monitored lakes in Washington County, Big Carnelian Lake ranks #7 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-30. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLimited data
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.
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A (Excellent)
Good clarity, visible to about 14.5 ft. Phosphorus level: 12 µg/L. Chlorophyll-a: 3.4 µg/L. Trophic State Index: 40.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 14.5 ft | Not graded |
| Phosphorus | 12 µg/L | Good |
| Chlorophyll-a (Algae) | 3.4 µg/L | Good |
| Trophic State Index (TSI) | 40 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Big Carnelian Lake
Compare lakeside cabins, hotels, and vacation rentals near Big Carnelian Lake in Washington 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.
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Water Temperature
Big Carnelian Lake typically sits around 77°F at the surface in August. Summer average is about 73°F. Usually warmest in Aug (about 77°F) and coldest in May (about 62°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 31 field readings (2022–2025) via the EPA Water Quality Portal.
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 66 ft |
| Average Depth | 26 ft |
| Surface Area | 457 acres |
| Shoreline Length | 5.1 mi |
| Littoral Zone | 29% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Big Carnelian LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Big Carnelian 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.
DNR Fisheries Survey Summary
15 surveys on file from MN DNR Fisheries. Most recent: 2025-08-04 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Bluntnose Minnow | 98.44 | — |
| SFS | 78.99 | — |
| Bluegill | 32.25 | 0.13 lb |
| BKF | 15.41 | — |
| BCS | 9.02 | — |
| Largemouth Bass | 7.07 | 0.74 lb |
CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.
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.
Bluegill
Largemouth Bass
From the 2025-08-04 survey
Big Carnelian Lake is a 457-acre, class 24 lake located in northern Washington County. Northern Pike is the primary management species in Big Carnelian Lake while Walleye and Largemouth Bass are secondary management species. A previously instituted 24-36 inch protected slot length for Northern Pike was dropped in 2020…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Big Carnelian Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — Big CarnelianFisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — Big CarnelianFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — Big CarnelianPublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: → Stable
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.078 m/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (34 observations).
Estimated open water season: 242 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2024-03-10 (2024) | 2008-04-23 (2008) |
| Ice-In | 2003-12-02 (2003) | 2024-01-15 (2024) |
Most recent ice-out: 2025-03-28
EPA Impairment Status
Big Carnelian 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 MN82-0049-00 · Official waterbody report
County Ranking
Ranked #7 of 75 lakes in Washington County
Nearby Lakes in Washington County
Frequently asked questions about Big Carnelian Lake
What is the water quality grade for Big Carnelian Lake?
- Big Carnelian Lake in Washington County, Minnesota has a water quality grade of A (Excellent). Water clarity: 14.5 ft visibility. Phosphorus: 12 µg/L. Chlorophyll-a (algae): 3.4 µg/L. Maximum depth: 66 ft. Surface area: 457.03 acres.
Is Big Carnelian Lake safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. Big Carnelian Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 3.4 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Big Carnelian Lake?
- Big Carnelian Lake typically sits around 77°F at the surface in August, from 31 EPA Water Quality Portal field readings (2022–2025). That is a typical value for the month, not a live reading.
How deep is Big Carnelian Lake?
- Big Carnelian Lake has a maximum depth of 66 feet and an average depth of 26 feet. The lake covers 457.03 acres.
What fish are in Big Carnelian Lake?
- Fish species found in Big Carnelian Lake include black bullhead, black crappie, bluegill, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, walleye, white sucker, yellow bullhead, yellow perch. Big Carnelian Lake is located in Washington County, Minnesota.
When does Big Carnelian Lake thaw?
- Big Carnelian Lake typically has ice-out around Apr 9. Ice typically forms around Dec 7. The open water season is approximately 242 days.
Are there boat ramps on Big Carnelian Lake?
- Big Carnelian Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Big Carnelian Lake. Public access is listed as yes.
Explore Big Carnelian Lake across LakeGrade
Depth, room, public access, and the state wake-sport rules
Fish species and top-graded lakes across Minnesota
Fish species and best lakes in Washington County
Species activity outlook by water temperature and season
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Lakes in the St. Croix Watershed, ranked by water quality
Moderate nutrients, good water quality
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Where this data comes from
167 measurements from 2 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
MNPCA167 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Colorimetry
- Analysis of Chlorophyll in Periphyton and Plankton
Monitoring station identifiers (2)
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
Named boat-access points from the USGS National Boat Ramps inventory
Ice data from Minnesota DNR Climate