Cottonwood Lake
Cottonwood Lake in Lyon County, Minnesota has a water quality grade of F (Algae-prone). 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.
- Clarity
- 1.8 ft
- Max depth
- 7 ft
- Area
- 383 acres
- Type
- Hypereutrophic
- Public access
- Yes
- Ice-out
- Mar 21
- Open water
- 253 days
Grade F measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Cottonwood Lake →
Next lake in Lyon County
Cottonwood Lake is a 383-acre highly nutrient-loaded hypereutrophic lake in Lyon County, Minnesota with a maximum depth of 7 feet. Water quality is graded F based on 2 sampling years through 2021. The lake supports 10 documented fish species including American eel, bigmouth buffalo, and black bullhead. Public access is available with 1 public boat landing. 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. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLimited data
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom
Water Quality Grade: F (Algae-prone)
Very murky, less than 1.8 ft of visibility. Phosphorus level: 154.5 µg/L. Chlorophyll-a: 64.5 µg/L. Trophic State Index: 72.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.8 ft | Not graded |
| Phosphorus | 154.5 µg/L | Poor |
| Chlorophyll-a (Algae) | 64.5 µg/L | Poor |
| Trophic State Index (TSI) | 72 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Where to stay 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 grade measures nutrients and algae, not lodging — cabins and rentals around Cottonwood Lake are listed below.
Top-rated places to stay near Cottonwood Lake
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Planning a whole trip? See where to stay at Minnesota’s top lakes →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 7 ft |
| Surface Area | 383 acres |
| Shoreline Length | 3.8 mi |
| Littoral Zone | 99% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Cottowood LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Cottonwood Lake
DNR Fisheries Survey Summary
12 surveys on file from MN DNR Fisheries. Most recent: 2025-09-08 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Fathead Minnow | 1306.14 | — |
| Black Bullhead | 81.93 | 0.32 lb |
| Walleye | 38.44 | 1.18 lb |
| Yellow Perch | 25.10 | 0.27 lb |
| OSS | 20.64 | 0.04 lb |
| Green Sunfish | 15.06 | 0.22 lb |
CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.
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
OSS
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
Ice Season
Historical ice data from Minnesota DNR (9 observations).
Estimated open water season: 253 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2024-03-01 (2024) | 2020-04-01 (2020) |
| Ice-In | 2024-11-28 (2024) | 2025-12-01 (2025) |
Most recent ice-out: 2026-03-21
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
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN42-0014-00 · Official waterbody report
County Ranking
Ranked #2 of 2 lakes in Lyon County
Nearby Lakes in Lyon County
Frequently asked questions about Cottonwood Lake
What is the water quality grade for Cottonwood Lake?
- Cottonwood Lake in Lyon County, Minnesota has a water quality grade of F (Algae-prone). 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?
- Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom. Cottonwood Lake has a water quality grade of F (Algae-prone). Algae concentration (chlorophyll-a) is 64.5 µg/L. Always check local health department advisories before swimming.
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.
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.
Are there boat ramps on Cottonwood Lake?
- Cottonwood Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Cottowood Lake. Public access is listed as yes.
Explore Cottonwood Lake across LakeGrade
Depth, room, public access, and the state wake-sport rules
Fish species and top-graded 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 grade
Very high nutrients, dense algae, poor clarity
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State Parks Near Cottonwood Lake
Other Grade F Lakes in Minnesota
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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)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated 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
Ice data from Minnesota DNR Climate