Rock Lake
Clearwater County, MinnesotaView mapDirections
Minnesota PCA publishes the water-quality measurements for Rock Lake. Here is what has been measured.
- Mesotrophic
- 19 ft max depth
- Public access
- Limited data
Rock Lake in Clearwater County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 11.2 ft visibility. Phosphorus: 16.5 µg/L. Chlorophyll-a (algae): 4.9 µg/L.
Rock Lake is a mesotrophic lake in Clearwater County, Minnesota with an estimated average depth of about 19 feet. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available. Compared to the 36 other monitored lakes in Clearwater County, Rock Lake ranks #5 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-04. Methodology: how these readings are compared.
What Rock Lake is good for
From access and monitoring records, not editorial picks.
- Clear water11.2 ft of visibility
Swimming conditions
Readings onlyLimited data
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. 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.
Good clarity, visible to about 11.2 ft. Phosphorus 16.5 µg/L. Chlorophyll-a 4.9 µg/L. TSI 44.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 11.2ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 16.5µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 4.9µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 44 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Rock Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Rock Lake typically sits around 64°F at the surface in September. Summer average is about 67°F. Usually warmest in Jul (about 69°F) and coldest in May (about 56°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (56°F) to its warmest (69°F).
Typical surface water temperature by month, from 47 field readings (2016–2025) via the EPA Water Quality Portal. See the full Rock Lake water temperature breakdown →
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Rock Lake. 2 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Aquatic Plant Report — Rock (1416)Aquatic Plant Report · MN DNR LakeFinder
- —Public Water Access Sites — RockPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
~19 ft est.
Public access
Yes
Listed by Minnesota PCA
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Minnesota has not published bathymetry for Rock Lake.
Lake Size & Watershed
Watershed (drainage) area
4 sq mi
HydroLAKES / HydroSHEDS
Surface area
54 acres
HydroLAKES / HydroSHEDS
Shoreline
1.5 mi
HydroLAKES / HydroSHEDS
Elevation
1,811 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Stays via Stay22
Stays near Rock Lake
Compare lakeside cabins, hotels, and vacation rentals near Rock Lake in Clearwater 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 Rock Lake
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Fishing Rock Lake
Water quality readings over time
2 seasons of samples on record (2024–2025). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Improving2 years
Phosphorus
Worsening+3.5 µg/L/yr2 years
Chlorophyll-a
Worsening+2.4 µg/L/yr2 years
Nearby Lakes in Clearwater County
Frequently asked questions about Rock Lake
Where is Rock Lake?
- Rock Lake is a lake in Clearwater 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 Clearwater County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 11.2 ft visibility. Phosphorus: 16.5 µg/L. Chlorophyll-a (algae): 4.9 µg/L.
Is Rock Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Rock Lake?
- Rock Lake typically sits around 64°F at the surface in September, from 47 EPA Water Quality Portal field readings (2016–2025). That is a typical value for the month, not a live reading.
How deep is Rock Lake?
- No published bathymetric survey covers Rock Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 19 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Can I fish at Rock Lake?
- Public access to Rock Lake is listed as yes on the lake record. 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
34 measurements from 2 monitoring stations, 2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Chippewa Tribe, Minnesota (White Earth Band) (Tribal)
WEARTH_WQX34 samples · 2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- Turbidity by Nephelometry
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder