Red Rock Lake
Douglas County, Minnesota904 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Red Rock Lake. Here is what has been measured.
- Eutrophic
- Impaired · Impaired biota (cause unknown)
- zebra mussel
- 22 ft max depth
- Public access
Red Rock Lake in Douglas County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 3.6 ft visibility. Phosphorus: 55 µg/L. Chlorophyll-a (algae): 33.7 µg/L. Maximum depth: 22 ft. Surface area: 904.1 acres.
Minnesota DNR's Standard Survey on June 2, 2025 caught 7.67 walleye per gill net at Red Rock Lake. DNR survey details →
Free interactive depth-contour map of Red Rock Lake, reaching a maximum surveyed depth of 20 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Minnesota DNR.
Red Rock Lake is a 904-acre productive, nutrient-rich eutrophic lake in Douglas County, Minnesota with a maximum depth of 22 feet (9-foot average). Overall water quality is declining over recent sampling years. The lake supports 13 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, Red Rock Lake ranks #34 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-22. Methodology: how these readings are compared.
Red Rock Lake covers about 900 acres in Douglas County. It has one public boat landing. The median ice-out date is April 7, which is when the open-water season begins. Vrbo is where to look for cabins and lake homes around Red Rock Lake, and Booking.com and Expedia search hotels near the lake for your dates.
What Red Rock Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
- Fishing13 species recorded
- Ice seasonIce-out around Apr 7
Swimming conditions
Readings onlyRecreation use not supported
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Red Rock Lake is listed impaired under Clean Water Act §303(d) (IR 5) for impaired biota (cause unknown), mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Red Rock 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 Red Rock Lake
These are the measurements Minnesota PCA publishes for Red Rock Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Murky, only visible to about 3.6 ft. Phosphorus 55 µg/L. Chlorophyll-a 33.7 µg/L. TSI 62.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 3.6ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 55µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 33.7µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 62 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Red Rock Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Red Rock Lake typically sits around 70°F at the surface in September. Summer average is about 73°F. Usually warmest in Jul (about 76°F) and coldest in May (about 59°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (59°F) to its warmest (76°F).
Typical surface water temperature by month, from 41 field readings (2011–2021) via the EPA Water Quality Portal. See the full Red Rock Lake water temperature breakdown →
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 moderate (54,450 cells/mL) on November 22, 2025.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Minnesota DNR's Standard Survey on June 2, 2025 caught 7.67 walleye per gill net at Red Rock Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Red Rock Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
15 surveys on file from MN DNR Fisheries. Most recent: 2025-06-02 (Standard Survey).
15 surveys on file · most recent 2025-06-02 (Standard Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Black Bullhead | 24.00 | 7–8 in 2025-06-02 | 0.7 lb |
| Yellow Perch | 20.33 | 5–10 in 2025-06-02 | 0.22 lb |
| Largemouth Bass | 16.41 | 8–18 in 2025-06-02 | 1.18 lb |
| Fathead Minnow | 15.24 | ||
| Black Crappie | 11.06 | 6–13 in 2025-06-02 | 0.25 lb |
| Bluegill | 8.82 | 3–10 in 2025-06-02 | 0.32 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.
Black Bullhead
Yellow Perch
Largemouth Bass
Black Crappie
From the 2025-06-02 survey
Red Rock Lake is a 902-acre shallow lake located approximately seven miles northeast of Hoffman. Maximum depth is 22 feet. Average depth is estimated at 9 feet. Water transparency has improved over time, averaging over 10 feet during early summer months since 2010. A trend in increasing water clarity is expected to…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Red Rock Lake. 4 reports 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
- —Aquatic Plant Report — Red Rock (0927)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — Red RockFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — Red RockPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
22 ft
Average depth
9.1 ft
Surface area
904 acres
Shoreline
11.7 mi
Littoral zone
57%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
10 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,293 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Red Rock LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Red Rock Lake
Compare lakeside cabins, hotels, and vacation rentals near Red Rock 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. The water-quality readings cover nutrients and algae, not lodging. Cabins and rentals around Red Rock Lake are listed below.
Top-rated places to stay near Red Rock Lake
Prices for Oct 9–11, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Minnesota’s top lakes →
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Fish Species
Click a species to see every 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.
Water Quality Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Water clarity
Worsening6 years
Phosphorus
Worsening+4.99 µg/L/yr6 years
Chlorophyll-a
Worsening+8.81 µg/L/yr6 years
Ice season
Typical ice-out
Apr 7
Earliest Mar 13, 2024 · Latest Apr 24, 2008
Typical ice-in
Nov 24
Earliest Nov 4, 1991 · Latest Dec 12, 2001
Most recent ice-out
Mar 13
2024
37 observations · Minnesota PCA ice records
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 5).
Causes of impairment
Designated uses not supporting: Aquatic life, Fish consumption, Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN21-0291-00 · Official waterbody report
Nearby Lakes in Douglas County
Frequently asked questions about Red Rock Lake
Where is Red Rock Lake?
- Red Rock Lake is a lake in Douglas County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Red Rock Lake?
- Red Rock Lake in Douglas County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 3.6 ft visibility. Phosphorus: 55 µg/L. Chlorophyll-a (algae): 33.7 µg/L. Maximum depth: 22 ft. Surface area: 904.1 acres.
Is Red Rock Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Red Rock Lake is listed impaired under Clean Water Act §303(d) (IR 5) for impaired biota (cause unknown), mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Red Rock Lake?
- Red Rock Lake typically sits around 70°F at the surface in September, from 41 EPA Water Quality Portal field readings (2011–2021). That is a typical value for the month, not a live reading.
How deep is Red Rock Lake?
- Red Rock Lake has a maximum depth of 22 feet and an average depth of 9.1 feet. The lake covers 904.1 acres.
What fish are in Red Rock Lake?
- Fish species found in Red Rock Lake include black bullhead, black crappie, bluegill, brown bullhead, common carp, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, walleye, yellow bullhead, yellow perch. Red Rock Lake is located in Douglas County, Minnesota.
What did the DNR fisheries survey find at Red Rock Lake?
- Minnesota DNR's Standard Survey on June 2, 2025 caught 7.67 walleye per gill net at Red Rock Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Red Rock Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
When does Red Rock Lake thaw?
- Red Rock Lake typically has ice-out around Apr 7. Ice typically forms around Nov 24. The open water season is approximately 231 days.
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 moderate (54,450 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Are there boat ramps on Red Rock Lake?
- Red Rock Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Red Rock Lake. Public access is listed as yes.
Can I fish at Red Rock Lake?
- Red Rock Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. 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 Red Rock Lake across LakeQuality
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Where this data comes from
84 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA84 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
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
Named boat-access points from the USGS National Boat Ramps inventory
Ice data from Minnesota DNR Climate