Mill Lake
Mill Lake in Douglas County, Minnesota has a water quality grade of C (Fair). Water clarity: 11 ft visibility. Phosphorus: 23 µg/L. Chlorophyll-a (algae): 9 µg/L. Maximum depth: 40 ft. Surface area: 451.12 acres.
- Clarity
- 11 ft
- Max depth
- 40 ft
- Area
- 451 acres
- Type
- Mesotrophic
- Trend
- ↓ Declining
- Public access
- Yes
- Ice-out
- Apr 11
- Open water
- 241 days
Next lake in Douglas County
Mill Lake is a 451-acre mesotrophic lake in Douglas County, Minnesota with a maximum depth of 40 feet (20-foot average). Water quality is graded C based on 2 sampling years through 2022. Overall water quality is declining over recent sampling years. The lake supports 15 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 1 public boat landing. Compared to the 36 other monitored lakes in Douglas County, Mill Lake ranks #27 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2022-09-14. Grade methodology: LakeGrade methodology.
Watch Mill Lake water quality
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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.
Generally safe for swimming, moderate water quality
Water Quality Grade: C (Fair)
Good clarity, visible to about 11 ft. Phosphorus level: 23 µg/L. Chlorophyll-a: 9 µg/L. Trophic State Index: 48.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 11 ft | Not graded |
| Phosphorus | 23 µg/L | Good |
| Chlorophyll-a (Algae) | 9 µg/L | Fair |
| Trophic State Index (TSI) | 48 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Mill Lake
Compare lakeside cabins, hotels, and vacation rentals near Mill Lake in Douglas 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.
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Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Mill Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was low (6,668 cells/mL) on November 29, 2025.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 40 ft |
| Average Depth | 20 ft |
| Surface Area | 451 acres |
| Shoreline Length | 5.4 mi |
| Littoral Zone | 44% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Mill LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Mill 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.
DNR Fisheries Survey Summary
13 surveys on file from MN DNR Fisheries. Most recent: 2024-06-11 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Bluntnose Minnow | 45.60 | — |
| SUN | 22.36 | — |
| Bluegill | 19.00 | 0.23 lb |
| Largemouth Bass | 17.63 | 0.87 lb |
| Yellow Perch | 15.69 | 0.12 lb |
| Yellow Bass | 13.87 | 0.66 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.
Bluegill
Largemouth Bass
Yellow Perch
Yellow Bass
From the 2024-06-11 survey
Mill Lake is a 461-acre, moderately productive basin located eight miles southwest of Alexandria. Maximum depth of the lake is 40.0 feet. Average depth is estimated at 20.0 feet. Water clarity has increased markedly in response to establishment of zebra mussels. Water transparency at time of the June 2024 survey was…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Mill Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — MillFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Mill (0929)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — MillFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — MillPublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: ↓ Declining
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.23 m/yr | 3 |
Ice Season
Historical ice data from Minnesota DNR (11 observations).
Estimated open water season: 241 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2016-03-21 (2016) | 2022-04-25 (2022) |
| Ice-In | 2018-11-13 (2018) | 2001-12-26 (2001) |
Most recent ice-out: 2022-04-25
EPA Impairment Status
Mill Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit MN21-0180-00 · Official waterbody report
County Ranking
Ranked #27 of 37 lakes in Douglas County
Nearby Lakes With Higher Grades
Mill Lake holds Grade C. 3 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
Nearby Lakes in Douglas County
Frequently asked questions about Mill Lake
What is the water quality grade for Mill Lake?
- Mill Lake in Douglas County, Minnesota has a water quality grade of C (Fair). Water clarity: 11 ft visibility. Phosphorus: 23 µg/L. Chlorophyll-a (algae): 9 µg/L. Maximum depth: 40 ft. Surface area: 451.12 acres.
Is Mill Lake safe to swim in?
- Generally safe for swimming, moderate water quality. Mill Lake has a water quality grade of C (Fair). Algae concentration (chlorophyll-a) is 9 µg/L. Always check local health department advisories before swimming.
How deep is Mill Lake?
- Mill Lake has a maximum depth of 40 feet and an average depth of 20 feet. The lake covers 451.12 acres.
What fish are in Mill Lake?
- Fish species found in Mill Lake include black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, common carp, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, walleye, white sucker, yellow bullhead, yellow perch. Mill Lake is located in Douglas County, Minnesota.
When does Mill Lake thaw?
- Mill Lake typically has ice-out around Apr 11. Ice typically forms around Dec 8. The open water season is approximately 241 days.
Does Mill Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Mill Lake (clouds, ice, or an off-season gap). The most recent reading was low (6,668 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Are there boat ramps on Mill Lake?
- Mill Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Mill Lake. Public access is listed as yes.
Explore Mill 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 Douglas County
Species activity outlook by water temperature and season
Top lakes and where to stay in the Alexandria Lakes area
Where to stay at Minnesota's top lakes, each with its grade
Lakes in the St. Croix Watershed, ranked by water quality
Lakes in the Lake Superior Basin (MN+WI), ranked by water quality
Lakes in the Sauk River Watershed, ranked by water quality
Moderate nutrients, good water quality
Minnesota's cleanest and most-polluted lakes, ranked
More Minnesota Lake Rankings
State Parks Near Mill Lake
Other Grade C Lakes in Minnesota
Mesotrophic Lakes in Minnesota
Compare Mill Lake With Nearby Lakes
Where this data comes from
46 measurements from 2 monitoring stations, 2020–2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA46 samples · 2020–2022
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (2)
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