Rocky Lake
St. Louis County, Minnesota120 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Rocky Lake. Here is what has been measured.
- 40 ft max depth
- Limited data
Rocky Lake in St. Louis County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 7 ft visibility. Maximum depth: 40 ft. Surface area: 119.68 acres.
Rocky Lake is a 120-acre lake in St. Louis County, Minnesota with a maximum depth of 40 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 2025-07-26. Methodology: how these readings are compared.
What Rocky Lake is good for
From access and monitoring records, not editorial picks.
- Deep water40 ft surveyed max depth
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Rocky 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 Rocky Lake
These are the measurements Minnesota PCA publishes for Rocky Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Moderate clarity, visible to about 7 ft. TSI 49.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 7ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | No reading The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. | |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 49 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Rocky Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
40 ft
Surface area
120 acres
Shoreline
3.3 mi
Littoral zone
35%
Share shallower than 15 ft
Public access
No
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
2 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,257 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
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Stays near Rocky Lake
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Fishing Rocky Lake
Water quality readings over time
2 seasons of samples on record (2022–2025). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Stable2 years
Nearby Lakes in St. Louis County
Frequently asked questions about Rocky Lake
Where is Rocky Lake?
- Rocky Lake is a lake in St. Louis County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Rocky Lake?
- Rocky Lake in St. Louis County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 7 ft visibility. Maximum depth: 40 ft. Surface area: 119.68 acres.
Is Rocky Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
How deep is Rocky Lake?
- Rocky Lake has a maximum depth of 40 feet. The lake covers 119.68 acres.
Can I fish at Rocky Lake?
- Public access to Rocky Lake is listed as no on the lake record, so confirm before you make the trip. 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.
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Where this data comes from
1 measurement from 1 monitoring station, 2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA1 sample · 2025
Analytical methods
- Field measurement/observation, generic method
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder