Red Rock Lake
Red Rock Lake in Cook County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 12 ft visibility. Maximum depth: 64 ft. Surface area: 450.9 acres.
- Clarity
- 12 ft
- Max depth
- 64 ft
- Area
- 451 acres
- Trend
- ↓ Declining
- Public access
- No
Next lake in Cook County
Why Red Rock 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 Red Rock Lake, the only measurement available is water clarity, which is not a water-quality indicator on its own — EPA's National Lakes Assessment does not grade clarity. Sampling here has recorded water clarity, but not 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.
Red Rock Lake is a 451-acre lake in Cook County, Minnesota with a maximum depth of 64 feet. Overall water quality is declining over recent sampling years. The lake supports 8 documented fish species including burbot, lake whitefish, and northern pike. No public access — the lake is private or restricted.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-06-29. 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 Red Rock Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Good clarity, visible to about 12 ft. Trophic State Index: 41.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 12 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 41 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Red Rock Lake
Compare lakeside cabins, hotels, and vacation rentals near Red Rock 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 Red Rock Lake
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Planning a whole trip? See where to stay at Minnesota’s top lakes →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Red Rock Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was high (469,894 cells/mL) on November 24, 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 | 64 ft |
| Surface Area | 451 acres |
| Shoreline Length | 12.9 mi |
| Littoral Zone | 32% |
| Public Access | No |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Red Rock 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
7 surveys on file from MN DNR Fisheries. Most recent: 2025-08-07 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| RBS | 15.50 | 0.05 lb |
| Tullibee (Cisco) | 5.33 | 0.92 lb |
| LKW | 4.78 | 3.13 lb |
| Walleye | 2.95 | 1.9 lb |
| Northern Pike | 2.58 | 2.75 lb |
| Yellow Perch | 1.69 | 0.16 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.
RBS
Tullibee (Cisco)
LKW
Walleye
From the 2025-08-07 survey
Temperature and dissolved oxygen measurements were collected from the deepest basin in Red Rock Lake on August 7th, 2025. This was done to evaluate the quantity and quality of cold, oxygenated water (i.e., oxythermal habitat) available to Lake Whitefish, the most sensitive coldwater species present in this lake…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Red Rock Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — Red RockFisheries Lake Survey · MN DNR LakeFinder
Water Quality Trend: ↓ Declining
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.104 m/yr | 4 |
EPA Impairment Status
Red Rock 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 MN16-0793-00 · Official waterbody report
Graded lakes near Red Rock Lake
Red Rock Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Cook County
Frequently asked questions about Red Rock Lake
What is the water quality grade for Red Rock Lake?
- Red Rock Lake in Cook County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 12 ft visibility. Maximum depth: 64 ft. Surface area: 450.9 acres.
Is Red Rock Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Red Rock Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
How deep is Red Rock Lake?
- Red Rock Lake has a maximum depth of 64 feet. The lake covers 450.9 acres.
What fish are in Red Rock Lake?
- Fish species found in Red Rock Lake include burbot, lake whitefish, northern pike, pumpkinseed, smallmouth bass, tullibee (cisco), walleye, white sucker. Red Rock Lake is located in Cook County, Minnesota.
Does Red Rock Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Red Rock Lake (clouds, ice, or an off-season gap). The most recent reading was high (469,894 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Explore Red Rock Lake across LakeGrade
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Where this data comes from
4 measurements from 4 monitoring stations, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA4 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
Monitoring station identifiers (4)
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