Cottonwood Lake
Lyon County, Minnesota383 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Cottonwood Lake. Here is what has been measured.
- Hypereutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- 7 ft max depth
- Public access
- Limited data
Cottonwood Lake in Lyon County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 1.8 ft visibility. Phosphorus: 154.5 µg/L. Chlorophyll-a (algae): 64.5 µg/L. Maximum depth: 7 ft. Surface area: 382.6 acres.
Minnesota DNR's Targeted Survey on September 8, 2025 caught 27.00 walleye per gill net at Cottonwood Lake. Length samples in the latest survey that recorded them ran 6–21 inches. DNR survey details →
Cottonwood Lake is a 383-acre highly nutrient-loaded hypereutrophic lake in Lyon County, Minnesota with a maximum depth of 7 feet. The lake supports 10 documented fish species including American eel, bigmouth buffalo, and black bullhead. Public access is available. Compared to the 1 other monitored lakes in Lyon County, Cottonwood Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2021-09-15. Methodology: how these readings are compared.
Cottonwood Lake covers about 380 acres in Lyon County. The median ice-out date is March 21, which is when the open-water season begins. Vrbo is where to look for cabins and lake homes around Cottonwood Lake, and Booking.com and Expedia search hotels near the lake for your dates.
What Cottonwood Lake is good for
From access and monitoring records, not editorial picks.
- Fishing10 species recorded
- Ice seasonIce-out around Mar 21
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. Cottonwood Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Cottonwood 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 Cottonwood Lake
These are the measurements Minnesota PCA publishes for Cottonwood 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 1.8 ft of visibility. Phosphorus 154.5 µg/L. Chlorophyll-a 64.5 µg/L. TSI 72.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 1.8ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 155µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 64.5µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 72 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about Cottonwood Lake
Answers come straight from the public measurements and survey records on this page.
Minnesota DNR's Targeted Survey on September 8, 2025 caught 27.00 walleye per gill net at Cottonwood Lake. Length samples in the latest survey that recorded them ran 6–21 inches.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Cottonwood Lake’s water-quality measurements separately. 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: 2025-09-08 (Targeted Survey).
12 surveys on file · most recent 2025-09-08 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Fathead Minnow | 1306.14 | ||
| Black Bullhead | 81.93 | 9–13 in 2025-09-08 | 0.32 lb |
| Walleye | 38.44 | 6–21 in 2025-09-08 | 1.18 lb |
| Yellow Perch | 25.10 | 4–12 in 2025-09-08 | 0.27 lb |
| Green Sunfish | 15.06 | 5–6 in 2012-06-28 | 0.22 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
Walleye
Yellow Perch
Green Sunfish
From the 2025-09-08 survey
A targeted gillnet survey was conducted during early September of 2025 on Cottonwood Lake. We conducted the survey to assess relative abundance and size structure of Northern Pike in Cottonwood Lake. A targeted survey is generally used for sampling a specific kind of fish or time of year (i.e. spawning season, fall…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Cottonwood Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — CottonwoodFisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — CottonwoodFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — CottonwoodPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
7 ft
Surface area
383 acres
Shoreline
3.8 mi
Littoral zone
99%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
27 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,050 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Stays via Stay22
Stays near Cottonwood Lake
Compare lakeside cabins, hotels, and vacation rentals near Cottonwood Lake in Lyon 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. The water-quality readings cover nutrients and algae, not lodging. Cabins and rentals around Cottonwood Lake are listed below.
Top-rated places to stay near Cottonwood 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 whole trip? See where to stay at Minnesota’s top lakes →
Follow Cottonwood Lake’s readings
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Fish Species
Click a species to see every lake where it is documented.
Fishing Cottonwood Lake
Ice season
Typical ice-out
Mar 21
Earliest Mar 1, 2024 · Latest Apr 1, 2020
Typical ice-in
Nov 29
Earliest Nov 28, 2024 · Latest Dec 1, 2025
Most recent ice-out
Mar 21
2026
9 observations · Minnesota PCA ice records
Reservoir Info (USACE NID)
Cottonwood Lake is a man-made reservoir impounded by the Cottonwood Lake (completed 1960), built primarily for grade stabilization on the Yellow Medicine River-TR; gravity-type dam, 9 ft tall.
- Surface area
- 378 ac
- Normal storage
- 2,765 ac-ft
- Max storage
- 3,582 ac-ft
- Drainage area
- 20.5 sq mi
- Hazard class
- Low
- Owner
- County of Lyon
Source: USACE National Inventory of Dams, NID ID MN00768 · Operator website
EPA Impairment Status
Cottonwood 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: Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN42-0014-00 · Official waterbody report
Nearby Lakes in Lyon County
Frequently asked questions about Cottonwood Lake
Where is Cottonwood Lake?
- Cottonwood Lake is a lake in Lyon County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Cottonwood Lake?
- Cottonwood Lake in Lyon County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 1.8 ft visibility. Phosphorus: 154.5 µg/L. Chlorophyll-a (algae): 64.5 µg/L. Maximum depth: 7 ft. Surface area: 382.6 acres.
Is Cottonwood Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Cottonwood Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
How deep is Cottonwood Lake?
- Cottonwood Lake has a maximum depth of 7 feet. The lake covers 382.6 acres.
What fish are in Cottonwood Lake?
- Fish species found in Cottonwood Lake include American eel, bigmouth buffalo, black bullhead, common carp, northern pike, orangespotted sunfish, walleye, white sucker, yellow bullhead, yellow perch. Cottonwood Lake is located in Lyon County, Minnesota.
What did the DNR fisheries survey find at Cottonwood Lake?
- Minnesota DNR's Targeted Survey on September 8, 2025 caught 27.00 walleye per gill net at Cottonwood Lake. Length samples in the latest survey that recorded them ran 6–21 inches. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Cottonwood Lake’s water-quality measurements separately. Catch rate is not a swim clearance and is not a weekly bite report.
When does Cottonwood Lake thaw?
- Cottonwood Lake typically has ice-out around Mar 21. Ice typically forms around Nov 29. The open water season is approximately 253 days.
Can I fish at Cottonwood Lake?
- Public access to Cottonwood Lake is listed as yes on the lake record. 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 Cottonwood Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
Fish species and the cleanest lakes across Minnesota
Fish species and best lakes in Lyon County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its readings
Minnesota's cleanest lakes, ranked on agency measurements
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Where this data comes from
15 measurements from 1 monitoring station, 2021. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA15 samples · 2021
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Ice data from Minnesota DNR Climate