Johnson Lake
St. Louis County, Minnesota456 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Johnson Lake. Here is what has been measured.
- Eutrophic
- Impaired · Mercury
- 18 ft max depth
- Public access
- Limited data
Johnson Lake in St. Louis County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 3 ft visibility. Phosphorus: 33 µg/L. Chlorophyll-a (algae): 9.8 µg/L. Maximum depth: 18 ft. Surface area: 455.98 acres.
Minnesota DNR's Standard Survey on June 6, 2022 caught 0.12 walleye per gill net at Johnson Lake. DNR survey details →
Johnson Lake is a 456-acre productive, nutrient-rich eutrophic lake in St. Louis County, Minnesota with a maximum depth of 18 feet. Overall water quality is declining over recent sampling years. The lake supports 11 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 1 public boat landing. Compared to the 67 other monitored lakes in St. Louis County, Johnson Lake ranks #50 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-15. Methodology: how these readings are compared.
What Johnson Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
- Fishing11 species recorded
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. Johnson Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether Johnson 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 Johnson Lake
These are the measurements Minnesota PCA publishes for Johnson 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 3 ft of visibility. Phosphorus 33 µg/L. Chlorophyll-a 9.8 µg/L. TSI 56.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 3ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 33µg/L | Fair GoodFairPoor |
| Chlorophyll-a (algae) | 9.8µg/L | Fair GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 56 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Johnson Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Johnson Lake typically sits around 52°F at the surface in October. Summer average is about 69°F. Usually warmest in Jul (about 70°F) and coldest in Oct (about 52°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (52°F) to its warmest (70°F).
Typical surface water temperature by month, from 39 field readings (2023–2025) via the EPA Water Quality Portal. See the full Johnson Lake water temperature breakdown →
Minnesota DNR's Standard Survey on June 6, 2022 caught 0.12 walleye per gill net at Johnson Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Johnson Lake’s water-quality measurements separately, and the water-quality trend over 3 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
10 surveys on file from MN DNR Fisheries. Most recent: 2022-06-06 (Standard Survey).
10 surveys on file · most recent 2022-06-06 (Standard Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluegill | 5.54 | 2–9 in 2022-06-06 | 0.22 lb |
| Black Bullhead | 5.49 | 4–15 in 2022-06-06 | 0.41 lb |
| Black Crappie | 4.10 | 3–11 in 2022-06-06 | 0.29 lb |
| White Sucker | 2.81 | 7–23 in 2022-06-06 | 2.04 lb |
| Northern Pike | 2.67 | 16–30 in 2022-06-06 | 2.28 lb |
| Yellow Perch | 1.72 | 4–7 in 2022-06-06 | 0.11 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
Black Bullhead
Black Crappie
White Sucker
From the 2022-06-06 survey
Johnson Lake is located approximately 6 miles south of Ely in the Superior National Forest. The rolling shoreline is forested in a pine-hardwood mix and is lightly developed by area standards. Maximum depth is 19 feet and much of the lake is shallower than 15 feet. A heavy bog stain limits water clarity, which was…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Johnson Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — JohnsonFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Johnson (1884)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — JohnsonFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — JohnsonPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
18 ft
Surface area
456 acres
Shoreline
10.6 mi
Littoral zone
93%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
14 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,414 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Johnson 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 Johnson Lake
Compare lakeside cabins, hotels, and vacation rentals near Johnson Lake in St. Louis 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 Johnson Lake
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Fish Species
Click a species to see every lake where it is documented.
Fishing Johnson Lake
Water quality readings over time
3 seasons of samples on record (2023–2025). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Worsening3 years
EPA Impairment Status
Johnson Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Fish consumption.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN69-0117-00 · Official waterbody report
Nearby Lakes in St. Louis County
Frequently asked questions about Johnson Lake
Where is Johnson Lake?
- Johnson 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 Johnson Lake?
- Johnson Lake in St. Louis County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 3 ft visibility. Phosphorus: 33 µg/L. Chlorophyll-a (algae): 9.8 µg/L. Maximum depth: 18 ft. Surface area: 455.98 acres.
Is Johnson Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Johnson Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
What is the water temperature of Johnson Lake?
- Johnson Lake typically sits around 52°F at the surface in October, from 39 EPA Water Quality Portal field readings (2023–2025). That is a typical value for the month, not a live reading.
How deep is Johnson Lake?
- Johnson Lake has a maximum depth of 18 feet. The lake covers 455.98 acres.
What fish are in Johnson Lake?
- Fish species found in Johnson Lake include black bullhead, black crappie, bluegill, burbot, largemouth bass, northern pike, pumpkinseed, rock bass, walleye, white sucker, yellow perch. Johnson Lake is located in St. Louis County, Minnesota.
What did the DNR fisheries survey find at Johnson Lake?
- Minnesota DNR's Standard Survey on June 6, 2022 caught 0.12 walleye per gill net at Johnson Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Johnson Lake’s water-quality measurements separately, and the water-quality trend over 3 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
Are there boat ramps on Johnson Lake?
- Johnson Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Johnson Lake. Public access is listed as yes.
Can I fish at Johnson Lake?
- Johnson 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 Johnson Lake across LakeQuality
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Where this data comes from
37 measurements from 1 monitoring station, 2023–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA37 samples · 2023–2025
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