Alder Lake
Cook County, Minnesota529 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Alder Lake. Here is what has been measured.
- Impaired · Mercury
- 72 ft max depth
- Limited data
Alder Lake in Cook County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 13.8 ft visibility. Phosphorus: 8 µg/L. Chlorophyll-a (algae): 3.1 µg/L. Maximum depth: 72 ft. Surface area: 528.93 acres.
Minnesota DNR's Standard Survey on June 15, 2015 caught 1.33 walleye per gill net at Alder Lake. Length samples in the latest survey that recorded them ran 13–23 inches. DNR survey details →
Alder Lake is a 529-acre lake in Cook County, Minnesota with a maximum depth of 72 feet. Limited fish-species data available. No public access — the lake is private or restricted.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2022-07-27. Methodology: how these readings are compared.
What Alder Lake is good for
From access and monitoring records, not editorial picks.
- Clear water13.8 ft of visibility
- Deep water72 ft surveyed max depth
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Alder Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether Alder 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 Alder Lake
These are the measurements Minnesota PCA publishes for Alder Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Good clarity, visible to about 13.8 ft. Phosphorus 8 µg/L. Chlorophyll-a 3.1 µg/L. TSI 38.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 13.8ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 8µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | 3.1µg/L | Measured, not scored The green pigment in algae — a direct measure of how much algae is in the water. |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 38 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Alder Lake
Answers come straight from the public measurements and survey records on this page.
Minnesota DNR's Standard Survey on June 15, 2015 caught 1.33 walleye per gill net at Alder Lake. Length samples in the latest survey that recorded them ran 13–23 inches.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Alder Lake’s water-quality measurements separately, and the water-quality trend over 2 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
9 surveys on file from MN DNR Fisheries. Most recent: 2025-08-13 (Targeted Survey).
9 surveys on file · most recent 2025-08-13 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Green Sunfish | 8.00 | ||
| Walleye | 1.57 | 13–23 in 2015-06-15 | 1.6 lb |
| White Sucker | 0.88 | 20–25 in 1999-07-12 | 2.66 lb |
| Lake Trout | 0.64 | 11–26 in 2015-06-15 | 3.11 lb |
| Yellow Perch | 0.42 | 5–9 in 2010-07-12 | 0.1 lb |
| Smallmouth Bass | 0.36 | 14–15 in 2015-06-15 | 1.01 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.
Walleye
White Sucker
Lake Trout
Yellow Perch
From the 2025-08-13 survey
Temperature and dissolved oxygen (DO) measurements were collected from the deepest basin in Alder Lake on August 13th, 2025, to evaluate the quantity and quality of cold, oxygenated water (i.e., oxythermal habitat) available to Lake Trout, the most sensitive coldwater species present in this lake. During the summer,…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Alder Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — AlderFisheries Lake Survey · MN DNR LakeFinder
Lake Details
Max depth
72 ft
Surface area
529 acres
Shoreline
10 mi
Littoral zone
25%
Share shallower than 15 ft
Public access
No
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
2 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,690 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Stays via Stay22
Stays near Alder Lake
Compare lakeside cabins, hotels, and vacation rentals near Alder Lake in Cook 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 Alder Lake
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Follow Alder Lake’s readings
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Fishing Alder Lake
Water quality readings over time
2 seasons of samples on record (2020–2022). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Stable2 years
EPA Impairment Status
Alder 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.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN16-0114-00 · Official waterbody report
Nearby Lakes in Cook County
Frequently asked questions about Alder Lake
Where is Alder Lake?
- Alder Lake is a lake in Cook County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Alder Lake?
- Alder Lake in Cook County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 13.8 ft visibility. Phosphorus: 8 µg/L. Chlorophyll-a (algae): 3.1 µg/L. Maximum depth: 72 ft. Surface area: 528.93 acres.
Is Alder Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Alder Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
How deep is Alder Lake?
- Alder Lake has a maximum depth of 72 feet. The lake covers 528.93 acres.
What did the DNR fisheries survey find at Alder Lake?
- Minnesota DNR's Standard Survey on June 15, 2015 caught 1.33 walleye per gill net at Alder Lake. Length samples in the latest survey that recorded them ran 13–23 inches. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Alder Lake’s water-quality measurements separately, and the water-quality trend over 2 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
Can I fish at Alder Lake?
- Public access to Alder Lake is listed as no on the lake record, so confirm before you make the trip. 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 Alder Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
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Fish species and best lakes in Cook County
Species activity outlook by water temperature and season
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Where this data comes from
5 measurements from 1 monitoring station, 2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA5 samples · 2022
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- 2130 B ~ Nephelometric Method
- 2120 B ~ Color in Water by Visual Comparison
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