Loon Lake
Waseca County, Minnesota125 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Loon Lake. Here is what has been measured.
- Eutrophic
- Impaired · Mercury
- 9 ft max depth
- Public access
- Limited data
Loon Lake in Waseca County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 2.5 ft visibility. Phosphorus: 121.5 µg/L. Chlorophyll-a (algae): 5.8 µg/L. Maximum depth: 9 ft. Surface area: 124.94 acres.
Minnesota DNR's Standard Survey on July 27, 2015 caught 1.33 walleye per gill net at Loon Lake. Length samples in the latest survey that recorded them ran 16–17 inches. DNR survey details →
Loon Lake is a 125-acre productive, nutrient-rich eutrophic lake in Waseca County, Minnesota with a maximum depth of 9 feet. Overall water quality is declining over recent sampling years. The lake supports 7 documented fish species including black bullhead, bluegill, and channel catfish. Public access is available with 1 public boat landing. Compared to the 1 other monitored lakes in Waseca County, Loon Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-10. Methodology: how these readings are compared.
What Loon Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
- Fishing7 species recorded
- Ice seasonIce-out around Mar 27
Swimming conditions
Readings onlyRecreation use not supported
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. 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 2.5 ft of visibility. Phosphorus 121.5 µg/L. Chlorophyll-a 5.8 µg/L. TSI 62.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 122µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 5.8µg/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. | 62 | 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 71°F at the surface in September. Summer average is about 77°F. Usually warmest in Jul (about 82°F) and coldest in May (about 54°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (54°F) to its warmest (82°F).
Typical surface water temperature by month, from 36 field readings (2022–2025) via the EPA Water Quality Portal. See the full Loon Lake water temperature breakdown →
Minnesota DNR's Standard Survey on July 27, 2015 caught 1.33 walleye per gill net at Loon Lake. Length samples in the latest survey that recorded them ran 16–17 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
12 surveys on file from MN DNR Fisheries. Most recent: 2023-04-19 (Targeted Survey).
12 surveys on file · most recent 2023-04-19 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluegill | 116.33 | 3–9 in 2015-07-27 | 0.18 lb |
| Black Bullhead | 112.22 | 5–11 in 2015-07-27 | 0.25 lb |
| Black Crappie | 53.93 | 5–9 in 2009-06-08 | 0.16 lb |
| Largemouth Bass | 25.90 | 10–11 in 2015-07-27 | 0.86 lb |
| Walleye | 13.47 | 16–17 in 2015-07-27 | 1.92 lb |
| Northern Pike | 6.44 | 14–20 in 2015-07-27 | 1.89 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.
Bluegill
Black Bullhead
Black Crappie
Largemouth Bass
From the 2023-04-19 survey
Three trap nets were set on 19 April 2023 to assess for winterkill. Yellow Perch and Black Bullheads were common and were the only species sampled. Loon Lake appears to have sustained a moderate winterkill.
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
9 ft
Surface area
125 acres
Shoreline
2.2 mi
Littoral zone
100%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
1 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,129 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
Stays via Stay22
Stays near Loon Lake
Compare lakeside cabins, hotels, and vacation rentals near Loon Lake in Waseca 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 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 (2022–2025). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Worsening3 years
Ice season
Typical ice-out
Mar 27
Earliest Feb 27, 2024 · Latest Apr 27, 2018
Typical ice-in
Dec 4
Earliest Nov 30, 2024 · Latest Jan 18, 2008
Most recent ice-out
Mar 23
2026
41 observations · Minnesota PCA ice records
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 MN81-0015-00 · Official waterbody report
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Loon Lake under Clean Water Act (NPDES) discharge permits, including 1 classified by the EPA as major discharger. 2 facilities have a reported Clean Water Act violation in the past three years.
- Waseca WwtpWaseca · 1.5 mi away · NPDES MN0020796MajorRecent violation
- Conagra Foods Packaged Foods LlcWaseca · 0.4 mi away · NPDES MN0001686Recent 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 Waseca County
Frequently asked questions about Loon Lake
Where is Loon Lake?
- Loon Lake is a lake in Waseca 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 Waseca County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 2.5 ft visibility. Phosphorus: 121.5 µg/L. Chlorophyll-a (algae): 5.8 µg/L. Maximum depth: 9 ft. Surface area: 124.94 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 71°F at the surface in September, from 36 EPA Water Quality Portal field readings (2022–2025). That is a typical value for the month, not a live reading.
How deep is Loon Lake?
- Loon Lake has a maximum depth of 9 feet. The lake covers 124.94 acres.
What fish are in Loon Lake?
- Fish species found in Loon Lake include black bullhead, bluegill, channel catfish, hybrid sunfish, largemouth bass, northern pike, yellow perch. Loon Lake is located in Waseca County, Minnesota.
What did the DNR fisheries survey find at Loon Lake?
- Minnesota DNR's Standard Survey on July 27, 2015 caught 1.33 walleye per gill net at Loon Lake. Length samples in the latest survey that recorded them ran 16–17 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.
When does Loon Lake thaw?
- Loon Lake typically has ice-out around Mar 27. Ice typically forms around Dec 4. The open water season is approximately 252 days.
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
33 measurements from 1 monitoring station, 2022–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA33 samples · 2022–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
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