Rock Lake
Wright County, Minnesota183 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Rock Lake. Here is what has been measured.
- Eutrophic
- Impaired · Impaired biota (cause unknown)
- Eurasian watermilfoil
- 37 ft max depth
- Public access
- Limited data
Rock Lake in Wright County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 2.6 ft visibility. Phosphorus: 64 µg/L. Chlorophyll-a (algae): 59.6 µg/L. Maximum depth: 37 ft. Surface area: 183.12 acres.
Minnesota DNR's Targeted Survey on August 11, 2025 caught 8.35 largemouth bass per hour of electrofishing at Rock Lake. Length samples in the latest survey that recorded them ran 4–18 inches. DNR survey details →
Rock Lake is a 183-acre productive, nutrient-rich eutrophic lake in Wright County, Minnesota with a maximum depth of 37 feet (14-foot average). 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 50 other monitored lakes in Wright County, Rock Lake ranks #33 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-14. Methodology: how these readings are compared.
What Rock Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
- Fishing15 species recorded
- Ice seasonIce-out around Apr 5
- Deep water37 ft surveyed max depth
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. Rock Lake is listed impaired under Clean Water Act §303(d) (IR 5) for impaired biota (cause unknown), nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether 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 Rock Lake
These are the measurements Minnesota PCA publishes for Rock Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 2.6 ft of visibility. Phosphorus 64 µg/L. Chlorophyll-a 59.6 µg/L. TSI 66.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2.6ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 64µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 59.6µg/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. | 66 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Rock Lake
Answers come straight from the public measurements and survey records on this page.
Minnesota DNR's Targeted Survey on August 11, 2025 caught 8.35 largemouth bass per hour of electrofishing at Rock Lake. Length samples in the latest survey that recorded them ran 4–18 inches.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Rock Lake’s water-quality measurements separately, and the water-quality trend over 2 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
8 surveys on file from MN DNR Fisheries. Most recent: 2025-08-11 (Targeted Survey).
8 surveys on file · most recent 2025-08-11 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluegill | 101.97 | 3–9 in 2016-08-15 | 0.2 lb |
| Green Sunfish | 34.91 | 6 in 2016-08-15 | 0.19 lb |
| Largemouth Bass | 17.91 | 4–18 in 2016-08-15 | 0.83 lb |
| Golden Shiner | 14.27 | 5–7 in 2016-08-15 | 0.09 lb |
| Black Crappie | 12.61 | 5–12 in 2016-08-15 | 0.35 lb |
| Yellow Bullhead | 7.97 | 7–14 in 2016-08-15 | 0.75 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.
Bluegill
Green Sunfish
Largemouth Bass
Golden Shiner
From the 2025-08-11 survey
A targeted survey of nearshore fish species in Rock Lake, was conducted on August 11th, 2025, by Area Fisheries staff. Sampling sites were evenly spaced around the lake, and each was sampled by backpack electrofishing and seining with a 50-foot or 15-foot seine, where possible. Backpack electrofishing was completed at…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for 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 — RockFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Rock (2017)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — RockFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — RockPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
37 ft
Average depth
13.6 ft
Surface area
183 acres
Shoreline
3 mi
Littoral zone
54%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
20 sq mi
HydroLAKES / HydroSHEDS
Elevation
974 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- 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 Rock Lake
Compare lakeside cabins, hotels, and vacation rentals near Rock Lake in Wright 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 Rock Lake are listed below.
Top-rated places to stay near 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 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 readings over time
2 seasons of samples on record (2020–2025). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Worsening2 years
Ice season
Typical ice-out
Apr 5
Earliest Mar 30, 2003 · Latest Apr 15, 2002
Typical ice-in
Dec 6
Earliest Nov 22, 2003 · Latest Dec 8, 2001
Most recent ice-out
Apr 6
2005
8 observations · Minnesota PCA ice records
EPA Impairment Status
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, Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN86-0182-00 · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Rock Lake under Clean Water Act (NPDES) discharge permits, including 1 classified by the EPA as major discharger. 1 facility has a reported Clean Water Act violation in the past three years.
- Annandale/Maple Lake/Howard Lake WwtpMaple Lake · 1.2 mi away · NPDES MN0066966MajorRecent violation
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
Nearby Lakes in Wright County
Frequently asked questions about Rock Lake
Where is Rock Lake?
- Rock Lake is a lake in Wright County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Rock Lake?
- Rock Lake in Wright County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 2.6 ft visibility. Phosphorus: 64 µg/L. Chlorophyll-a (algae): 59.6 µg/L. Maximum depth: 37 ft. Surface area: 183.12 acres.
Is Rock Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Rock Lake is listed impaired under Clean Water Act §303(d) (IR 5) for impaired biota (cause unknown), nutrients (phosphorus, nitrogen). Check local advisories before you swim.
How deep is Rock Lake?
- Rock Lake has a maximum depth of 37 feet and an average depth of 13.6 feet. The lake covers 183.12 acres.
What fish are in Rock Lake?
- Fish species found in Rock Lake include black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, common carp, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, walleye, white crappie, yellow bullhead, yellow perch. Rock Lake is located in Wright County, Minnesota.
What did the DNR fisheries survey find at Rock Lake?
- Minnesota DNR's Targeted Survey on August 11, 2025 caught 8.35 largemouth bass per hour of electrofishing at Rock Lake. Length samples in the latest survey that recorded them ran 4–18 inches. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Rock Lake’s water-quality measurements separately, and the water-quality trend over 2 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
When does Rock Lake thaw?
- Rock Lake typically has ice-out around Apr 5. Ice typically forms around Dec 6. The open water season is approximately 245 days.
Are there boat ramps on Rock Lake?
- Rock Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Rock Lake. Public access is listed as yes.
Can I fish at Rock Lake?
- 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 Rock Lake across LakeQuality
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Where this data comes from
23 measurements from 2 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
MNPCA23 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 (2)
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
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