Loon Lake
Blue Earth County, Minnesota809 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Loon Lake. Here is what has been measured.
- Impaired · Mercury
- 7 ft max depth
- Public access
- Limited data
Loon Lake in Blue Earth County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 2 ft visibility. Maximum depth: 7 ft. Surface area: 808.62 acres.
Minnesota DNR's Standard Survey on August 15, 2022 caught 14.67 walleye per gill net at Loon Lake. Length samples in the latest survey that recorded them ran 8–26 inches. DNR survey details →
Free interactive depth-contour map of Loon Lake, reaching a maximum surveyed depth of 5 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Minnesota DNR.
Loon Lake is a 809-acre lake in Blue Earth County, Minnesota with a maximum depth of 7 feet. Overall water quality is declining over recent sampling years. The lake supports 13 documented fish species including bigmouth buffalo, black bullhead, and black crappie. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2022-06-24. Methodology: how these readings are compared.
What Loon Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
- Fishing13 species recorded
Swimming conditions
No readingRecreation use not supported
Nutrient and algae readings are not a swimming clearance. Loon Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Loon 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 Loon Lake
These are the measurements Minnesota PCA publishes for Loon Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 2 ft of visibility. TSI 67.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | No reading The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. | |
| 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. | 67 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Loon Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Loon Lake typically sits around 73°F at the surface in September. Summer average is about 77°F. Usually warmest in Aug (about 83°F) and coldest in Jun (about 71°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (71°F) to its warmest (83°F).
Typical surface water temperature by month, from 10 field readings (2016–2016) via the EPA Water Quality Portal. See the full Loon Lake water temperature breakdown →
Minnesota DNR's Standard Survey on August 15, 2022 caught 14.67 walleye per gill net at Loon Lake. Length samples in the latest survey that recorded them ran 8–26 inches.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Loon Lake’s water-quality measurements separately, and the water-quality trend over 3 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
8 surveys on file from MN DNR Fisheries. Most recent: 2022-08-15 (Standard Survey).
8 surveys on file · most recent 2022-08-15 (Standard Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Black Bullhead | 64.32 | 4–12 in 2022-08-15 | 0.45 lb |
| Common Carp | 29.06 | 5–27 in 2022-08-15 | 2.93 lb |
| Black Crappie | 19.40 | 3–12 in 2022-08-15 | 0.28 lb |
| Walleye | 16.10 | 8–26 in 2022-08-15 | 1.11 lb |
| Yellow Perch | 11.17 | 5–10 in 2022-08-15 | 0.21 lb |
| Bluegill | 7.09 | 3–8 in 2022-08-15 | 0.24 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.
Black Bullhead
Common Carp
Black Crappie
Walleye
From the 2022-08-15 survey
Loon Lake is an 809-acre lake located east of the city of Lake Crystal in northwest Blue Earth County. A DNR-maintained public access is located on the south side of the lake off County Road 9. Loon Lake is shallow with a maximum depth of 7 feet with generally poor water clarity and frequent algal blooms caused by…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Loon Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — LoonFisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — LoonFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — LoonPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
7 ft
Surface area
809 acres
Shoreline
5.3 mi
Littoral zone
100%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
7 sq mi
HydroLAKES / HydroSHEDS
Elevation
965 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Loon LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
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Stays near Loon Lake
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Top-rated places to stay near Loon Lake
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Follow Loon Lake’s readings
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Fish Species
Click a species to see every lake where it is documented.
Fishing Loon Lake
Water quality readings over time
3 seasons of samples on record (2020–2022). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Worsening3 years
EPA Impairment Status
Loon 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: Fish consumption, Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN07-0096-00 · Official waterbody report
Nearby Lakes in Blue Earth County
Frequently asked questions about Loon Lake
Where is Loon Lake?
- Loon Lake is a lake in Blue Earth County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Loon Lake?
- Loon Lake in Blue Earth County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 2 ft visibility. Maximum depth: 7 ft. Surface area: 808.62 acres.
Is Loon Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Loon Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Loon Lake?
- Loon Lake typically sits around 73°F at the surface in September, from 10 EPA Water Quality Portal field readings (2016–2016). That is a typical value for the month, not a live reading.
How deep is Loon Lake?
- Loon Lake has a maximum depth of 7 feet. The lake covers 808.62 acres.
What fish are in Loon Lake?
- Fish species found in Loon Lake include bigmouth buffalo, black bullhead, black crappie, bluegill, brown bullhead, common carp, hybrid sunfish, northern pike, walleye, white crappie, white sucker, yellow bullhead, yellow perch. Loon Lake is located in Blue Earth County, Minnesota.
What did the DNR fisheries survey find at Loon Lake?
- Minnesota DNR's Standard Survey on August 15, 2022 caught 14.67 walleye per gill net at Loon Lake. Length samples in the latest survey that recorded them ran 8–26 inches. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Loon Lake’s water-quality measurements separately, and the water-quality trend over 3 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
Are there boat ramps on Loon Lake?
- Loon Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Loon Lake. Public access is listed as yes.
Can I fish at Loon Lake?
- Loon 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 Minnesota's fish and wildlife agency, so check its current regulations before you go.
Explore Loon Lake across LakeQuality
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Where this data comes from
4 measurements from 1 monitoring station, 2020–2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA4 samples · 2020–2022
Analytical methods
- Field measurement/observation, generic method
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory