Johnson Lake
St. Louis County, MinnesotaLimited DataEutrophic
On the LakeGrade rubric Johnson Lake fails the cutoffs — a TSI of 61 and persistent algal pressure put it in the bottom tier.
Eutrophic conditions are the baseline here: clarity drops noticeably in late summer, and dissolved oxygen near the bottom can become a concern. The lake bottoms out at 18 ft — a moderate depth that supports a warm-water fishery without the year-round cold refuge a deeper basin provides. At 456 acres, Johnson Lake fits the Minnesota median for monitored lakes, with 10.6 miles of shoreline. Johnson Lake ranks 184 of 187 in St. Louis County — at the lower end of the locally monitored distribution.
No invasive species are currently listed at Johnson Lake — the lake remains off the Minnesota infested-waters roster. Walleye are documented at Johnson Lake, one of 11 fish species on record for the lake. Public access is available — the lake is on the Minnesota PCA public-access list. Monitoring depth is thin here: the LakeGrade rubric is applied to a small number of sample years, and the grade will be revised as more data accumulates.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-10-21. Grade methodology: LakeGrade methodology.
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Swimming Safety
Avoid swimming, very poor water quality, potential algae toxins
Water Quality Grade: F, Very Poor
Very murky, less than 3 ft of visibility. Trophic State Index: 61.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 61 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 18 ft |
| Surface Area | 455.98 acres |
| Shoreline Length | 10.6 mi |
| Littoral Zone | 93% |
| Public Access | Yes |
Fish Species
Click a species to see all Minnesota and Wisconsin lakes where it is found.
→ Best fishing times for Johnson Lake (14-day solunar calendar)
→ Is it safe to eat fish from Johnson Lake? (mercury & PFAS guide)
→ Johnson Lake fishing regulations (limits, seasons, special rules)
Water Quality Trend: ↓ Declining
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.31 m/yr | 2 |
Location
County Ranking
Ranked #184 of 187 lakes in St. Louis County
Cleaner Lakes Within 30 Miles
Johnson Lake holds Grade F. One nearby lake has a higher grade.
Nearby Lakes in St. Louis County
More Minnesota Lake Rankings
State Parks Near Johnson Lake
Other Grade F Lakes in Minnesota
Eutrophic Lakes in Minnesota
Compare Johnson Lake With Nearby Lakes
DNR Fisheries Survey Summary
10 surveys on file from MN DNR Fisheries. Most recent: 2022-06-06 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Bluegill | 5.54 | 0.22 lb |
| Black Bullhead | 5.49 | 0.41 lb |
| Black Crappie | 4.10 | 0.29 lb |
| White Sucker | 2.81 | 2.04 lb |
| Northern Pike | 2.67 | 2.28 lb |
| Yellow Perch | 1.72 | 0.11 lb |
CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.
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.
- —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
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
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN69-0117-00 · Official waterbody report
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Grading methodology based on Metropolitan Council standards
Lake details from Minnesota DNR LakeFinder
Most recent sample: 2024-10-21
Monitoring stations: 1