Carlos Lake
Douglas County, Minnesota2,605 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Carlos Lake. Here is what has been measured.
- Oligotrophic
- Impaired · Mercury
- 2 aquatic invasives
- 163 ft max depth
- Public access
Carlos Lake in Douglas County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 18 ft visibility. Phosphorus: 13.5 µg/L. Chlorophyll-a (algae): 2.1 µg/L. Maximum depth: 163 ft. Surface area: 2605.11 acres.
Minnesota DNR's Targeted Survey on August 20, 2024 caught 0.42 walleye per hour of electrofishing at Carlos Lake. DNR survey details →
Free interactive depth-contour map of Carlos Lake, reaching a maximum surveyed depth of 150 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Minnesota DNR.
Carlos Lake is a 2,605-acre cold, clear oligotrophic lake in Douglas County, Minnesota with a maximum depth of 163 feet (50-foot average). Overall water quality is declining over recent sampling years. The lake supports 21 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 2 public boat landings. Compared to the 36 other monitored lakes in Douglas County, Carlos Lake ranks #18 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-10-01. Methodology: how these readings are compared.
Carlos Lake covers about 2,600 acres in Douglas County. It has 2 public boat landings, so a lakefront rental is not the only way to get a boat on the water. The median ice-out date is April 21, which is when the open-water season begins. Vrbo is where to look for cabins and lake homes around Carlos Lake, and Booking.com and Expedia search hotels near the lake for your dates.
What Carlos Lake is good for
From access and monitoring records, not editorial picks.
- Clear water18 ft of visibility
- Boat launch2 documented ramps
- Fishing21 species recorded
- Ice seasonIce-out around Apr 21
- Deep water163 ft surveyed max depth
- Big water2,605 acres
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. Carlos Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury. Check local advisories before you swim.
Whether Carlos Lake is safe to swim in today is a call for the Minnesota Pollution Control Agency and the Minnesota DNR and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Carlos Lake
These are the measurements Minnesota PCA publishes for Carlos Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Crystal clear, you can see 18 ft down. Phosphorus 13.5 µg/L. Chlorophyll-a 2.1 µg/L. TSI 38.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 18ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 13.5µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 2.1µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 38 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Carlos Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Carlos Lake typically sits around 67°F at the surface in September. Summer average is about 72°F. Usually warmest in Jul (about 76°F) and coldest in May (about 47°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (47°F) to its warmest (76°F).
Typical surface water temperature by month, from 63 field readings (2011–2025) via the EPA Water Quality Portal. See the full Carlos Lake water temperature breakdown →
Minnesota DNR's Targeted Survey on August 20, 2024 caught 0.42 walleye per hour of electrofishing at Carlos Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Carlos Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
14 surveys on file from MN DNR Fisheries. Most recent: 2024-08-20 (Targeted Survey).
14 surveys on file · most recent 2024-08-20 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluntnose Minnow | 35.04 | ||
| Largemouth Bass | 18.69 | 3–19 in 2024-07-22 | 0.69 lb |
| Bluegill | 18.02 | 2–7 in 2024-07-22 | 0.14 lb |
CPUE = catch per unit effort, fish caught per net per set in a standardised survey. It measures abundance, not size, and 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.
Largemouth Bass
Bluegill
From the 2024-08-20 survey
A targeted survey of nearshore fish species in Lake Carlos was conducted beginning on August 20, 2024, by Index of Biological Integrity (IBI) Program staff. Sampling sites were evenly spaced around the lake, and each was sampled by backpack electrofishing and seining with a 50-foot or 15-foot seine, where possible.…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Carlos Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — CarlosFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Carlos (1074)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — CarlosFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — CarlosPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
163 ft
Average depth
50 ft
Surface area
2,605 acres
Shoreline
12.8 mi
Littoral zone
35%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Recreation & Access
- Lake Carlos (East)Public
- Lake Carlos (West)Public
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Carlos Lake
Compare lakeside cabins, hotels, and vacation rentals near Carlos Lake in Douglas 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 Carlos 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 trip? Cabins and lodging at Carlos Lake → · more Minnesota lake trips
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Fish Species
Click a species to see every lake where it is documented.
Fishing Carlos 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 6 years of monitoring (2020–2025).
Water clarity
Worsening6 years
Phosphorus
Worsening+0.6 µg/L/yr6 years
Chlorophyll-a
Stable0 µg/L/yr6 years
Ice season
Typical ice-out
Apr 21
Earliest Mar 12, 2024 · Latest May 13, 2013
Most recent ice-out
Mar 12
2024
17 observations · Minnesota PCA ice records
Reservoir Info (USACE NID)
Carlos Lake is a man-made reservoir impounded by the Lake Carlos (completed 1993), built primarily for recreation on the Long Prairie River; other-type dam, 7 ft tall.
- Surface area
- 183 ac
- Normal storage
- 156,000 ac-ft
- Max storage
- 156,000 ac-ft
- Drainage area
- 247 sq mi
- Hazard class
- Undetermined
- Owner
- MNDNR
Source: USACE National Inventory of Dams, NID ID MN01118 · Operator website
EPA Impairment Status
Carlos Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Fish consumption.
Source: EPA ATTAINS assessment unit MN21-0057-00 · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Carlos Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Carlos WwtpCarlos · 3.3 mi away · NPDES MN0023019Recent 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 Douglas County
Frequently asked questions about Carlos Lake
Where is Carlos Lake?
- Carlos Lake is a lake in Douglas County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Carlos Lake?
- Carlos Lake in Douglas County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 18 ft visibility. Phosphorus: 13.5 µg/L. Chlorophyll-a (algae): 2.1 µg/L. Maximum depth: 163 ft. Surface area: 2605.11 acres.
Is Carlos Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Carlos Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury. Check local advisories before you swim.
What is the water temperature of Carlos Lake?
- Carlos Lake typically sits around 67°F at the surface in September, from 63 EPA Water Quality Portal field readings (2011–2025). That is a typical value for the month, not a live reading.
How deep is Carlos Lake?
- Carlos Lake has a maximum depth of 163 feet and an average depth of 50 feet. The lake covers 2605.11 acres.
What fish are in Carlos Lake?
- Fish species found in Carlos Lake include black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, common carp, greater redhorse, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, rock bass, shorthead redhorse, smallmouth bass, sunfish, tullibee (cisco), walleye, white sucker, yellow bullhead, yellow perch. Carlos Lake is located in Douglas County, Minnesota.
What did the DNR fisheries survey find at Carlos Lake?
- Minnesota DNR's Targeted Survey on August 20, 2024 caught 0.42 walleye per hour of electrofishing at Carlos Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Carlos Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
When does Carlos Lake thaw?
- Carlos Lake typically has ice-out around Apr 21.
Are there boat ramps on Carlos Lake?
- Carlos Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Lake Carlos (East), Lake Carlos (West). Public access is listed as yes.
Can I fish at Carlos Lake?
- Carlos Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Minnesota's fish and wildlife agency, so check its current regulations before you go.
Explore Carlos Lake across LakeQuality
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Fish species and best lakes in Douglas County
Species activity outlook by water temperature and season
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Compare Carlos Lake With Nearby Lakes
Douglas County · 18.7 ft
Douglas County · 16.4 ft
Douglas County · 13.1 ft
Douglas County · 14 ft
Douglas County · 13 ft
Douglas County · 9.8 ft
Where this data comes from
175 measurements from 4 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
MNPCA175 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
- Phosphorus by Colorimetry
Monitoring station identifiers (4)
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)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory
Ice data from Minnesota DNR Climate