Koronis Lake
Stearns County, Minnesota2,968 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Koronis Lake. Here is what has been measured.
- Eutrophic
- Impaired · Impaired biota (cause unknown)
- zebra mussel
- 132 ft max depth
- Public access
Koronis Lake in Stearns County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 6 ft visibility. Phosphorus: 27 µg/L. Chlorophyll-a (algae): 13.8 µg/L. Maximum depth: 132 ft. Surface area: 2968.28 acres.
Minnesota DNR's Standard Survey on July 29, 2024 caught 27.00 walleye per gill net at Koronis Lake. Length samples in the latest survey that recorded them ran 5–12 inches. DNR survey details →
Free interactive depth-contour map of Koronis Lake, reaching a maximum surveyed depth of 130 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Minnesota DNR.
Koronis Lake is a 2,968-acre productive, nutrient-rich eutrophic lake in Stearns County, Minnesota with a maximum depth of 132 feet (29-foot average). Overall water quality is declining over recent sampling years. The lake supports 22 documented fish species including bigmouth buffalo, black bullhead, and black crappie. Public access is available with 3 public boat landings. Compared to the 31 other monitored lakes in Stearns County, Koronis Lake ranks #11 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-15. Methodology: how these readings are compared.
Koronis Lake covers about 3,000 acres in Stearns County. It has 3 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 14, which is when the open-water season begins. Vrbo is where to look for cabins and lake homes around Koronis Lake, and Booking.com and Expedia search hotels near the lake for your dates.
What Koronis Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch3 documented ramps
- Fishing22 species recorded
- Ice seasonIce-out around Apr 14
- Deep water132 ft surveyed max depth
- Big water2,968 acres
Swimming conditions
Readings onlyModerate 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. Koronis Lake is listed impaired under Clean Water Act §303(d) (IR 5) for impaired biota (cause unknown), mercury. Check local advisories before you swim.
Whether Koronis 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 Koronis Lake
These are the measurements Minnesota PCA publishes for Koronis Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Murky, only visible to about 6 ft. Phosphorus 27 µg/L. Chlorophyll-a 13.8 µg/L. TSI 53.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 6ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 27µg/L | Fair GoodFairPoor |
| Chlorophyll-a (algae) | 13.8µg/L | Fair GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 53 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Koronis Lake
Answers come straight from the public measurements and survey records on this page.
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Koronis Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was moderate (33,113 cells/mL) on June 12, 2026.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Minnesota DNR's Standard Survey on July 29, 2024 caught 27.00 walleye per gill net at Koronis Lake. Length samples in the latest survey that recorded them ran 5–12 inches.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Koronis 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
31 surveys on file from MN DNR Fisheries. Most recent: 2025-10-23 (Targeted Survey).
31 surveys on file · most recent 2025-10-23 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Yellow Perch | 33.36 | 4–9 in 2024-07-29 | 0.13 lb |
| Walleye | 29.06 | 5–12 in 2025-10-23 | 1.05 lb |
| Bluntnose Minnow | 16.84 | ||
| Bluegill | 14.58 | 3–8 in 2024-07-29 | 0.17 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.
Yellow Perch
Walleye
Bluegill
From the 2025-10-23 survey
A targeted fall night electrofishing survey was conducted for young of year "YOY" (fingerling sized) Walleye on Koronis during October 23, 2025. A targeted survey is generally used for sampling a specific kind of fish or time of year (i.e. spawning season, fall season, etc.) unlike a standard survey which samples a…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Koronis Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — Koronis (main lake)Fisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — Koronis (main lake)Fish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — Koronis (main lake)Public Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
132 ft
Average depth
29 ft
Surface area
2,968 acres
Shoreline
15.8 mi
Littoral zone
40%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
317 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,115 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Highway 55 BridgePublic
- Koronis Lake County ParkPublic
- Koronis Lake ParkPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Koronis Lake
Compare lakeside cabins, hotels, and vacation rentals near Koronis Lake in Stearns 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 Koronis Lake
Prices for Oct 9–11, 4 adults. Change dates on the map below.
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Planning a trip? Cabins and lodging at Koronis Lake → · more Minnesota lake trips
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Fish Species
Click a species to see every lake where it is documented.
Fishing Koronis 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+1.67 µg/L/yr6 years
Chlorophyll-a
Worsening+1.78 µg/L/yr6 years
Ice season
Typical ice-out
Apr 14
Earliest Apr 3, 2004 · Latest Apr 28, 2023
Typical ice-in
Dec 1
Earliest Nov 29, 1977 · Latest Dec 6, 1986
Most recent ice-out
Apr 28
2023
10 observations · Minnesota PCA ice records
Reservoir Info (USACE NID)
Koronis Lake is a man-made reservoir impounded by the Lake Koronis (completed 1989), built primarily for recreation on the Crow River; concrete-type dam, 9 ft tall.
- Surface area
- 3,034 ac
- Normal storage
- 9,112 ac-ft
- Max storage
- 90,000 ac-ft
- Drainage area
- 307 sq mi
- Hazard class
- Low
Source: USACE National Inventory of Dams, NID ID MN01547 · Operator website
EPA Impairment Status
Koronis 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: Aquatic life, Fish consumption.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN73-0200-02 · Official waterbody report
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Koronis Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Ampi - PaynesvillePaynesville · 2.8 mi away · NPDES MN0044326Recent violation
- PaynesvillePaynesville · 2.8 mi away · NPDES MN0020168
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 Stearns County
Frequently asked questions about Koronis Lake
Where is Koronis Lake?
- Koronis Lake is a lake in Stearns County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Koronis Lake?
- Koronis Lake in Stearns County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 6 ft visibility. Phosphorus: 27 µg/L. Chlorophyll-a (algae): 13.8 µg/L. Maximum depth: 132 ft. Surface area: 2968.28 acres.
Is Koronis Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Koronis Lake is listed impaired under Clean Water Act §303(d) (IR 5) for impaired biota (cause unknown), mercury. Check local advisories before you swim.
How deep is Koronis Lake?
- Koronis Lake has a maximum depth of 132 feet and an average depth of 29 feet. The lake covers 2968.28 acres.
What fish are in Koronis Lake?
- Fish species found in Koronis Lake include bigmouth buffalo, black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, common carp, golden redhorse, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, river redhorse, rock bass, shorthead redhorse, smallmouth bass, tullibee (cisco), walleye, white sucker, yellow bullhead, yellow perch. Koronis Lake is located in Stearns County, Minnesota.
What did the DNR fisheries survey find at Koronis Lake?
- Minnesota DNR's Standard Survey on July 29, 2024 caught 27.00 walleye per gill net at Koronis Lake. Length samples in the latest survey that recorded them ran 5–12 inches. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Koronis 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 Koronis Lake thaw?
- Koronis Lake typically has ice-out around Apr 14. Ice typically forms around Dec 1. The open water season is approximately 231 days.
Does Koronis Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Koronis Lake (clouds, ice, or an off-season gap). The most recent reading was moderate (33,113 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Are there boat ramps on Koronis Lake?
- Koronis Lake has 3 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Highway 55 Bridge, Koronis Lake County Park, Koronis Lake Park. Public access is listed as yes.
Can I fish at Koronis Lake?
- Koronis Lake has 3 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 Koronis Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
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Fish species and best lakes in Stearns County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its readings
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Where this data comes from
212 measurements from 3 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
MNPCA212 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (3)
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