Alder Lake
Alder Lake in Cook County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. 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.
- Clarity
- 13.8 ft
- Max depth
- 72 ft
- Area
- 529 acres
- Trend
- → Stable
- Public access
- No
Next lake in Cook County
Why Alder Lake has no grade
We grade a lake only when its monitoring record clears the evidence bar: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Alder Lake, no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). Sampling here has recorded water clarity, phosphorus and algae (chlorophyll-a).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by MPCA and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
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. Grade methodology: LakeGrade methodology.
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Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Alder Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Good clarity, visible to about 13.8 ft. Phosphorus level: 8 µg/L. Chlorophyll-a: 3.1 µg/L. Trophic State Index: 38.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 13.8 ft | Not graded |
| Phosphorus | 8 µg/L | Not graded |
| Chlorophyll-a (Algae) | 3.1 µg/L | Not graded |
| Trophic State Index (TSI) | 38 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay 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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Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 72 ft |
| Surface Area | 529 acres |
| Shoreline Length | 10 mi |
| Littoral Zone | 25% |
| Public Access | No |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Fishing Alder Lake
DNR Fisheries Survey Summary
9 surveys on file from MN DNR Fisheries. Most recent: 2025-08-13 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Green Sunfish | 8.00 | — |
| Walleye | 1.57 | 1.6 lb |
| White Sucker | 0.88 | 2.66 lb |
| Lake Trout | 0.64 | 3.11 lb |
| Yellow Perch | 0.42 | 0.1 lb |
| Smallmouth Bass | 0.36 | 1.01 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.
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
Water Quality Trend: → Stable
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.035 m/yr | 2 |
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
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN16-0114-00 · Official waterbody report
Graded lakes near Alder Lake
Alder Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Cook County
Frequently asked questions about Alder Lake
What is the water quality grade for Alder Lake?
- Alder Lake in Cook County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. 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?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Alder Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Algae concentration (chlorophyll-a) is 3.1 µg/L. Always check local health department advisories before swimming.
How deep is Alder Lake?
- Alder Lake has a maximum depth of 72 feet. The lake covers 528.93 acres.
Explore Alder Lake across LakeGrade
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)
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