South Lake
South Lake in Cook County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 26 ft visibility. Maximum depth: 140 ft. Surface area: 1144.75 acres.
- Clarity
- 26 ft
- Max depth
- 140 ft
- Area
- 1,145 acres
- Trend
- ↑ Improving
- Public access
- No
Next lake in Cook County
Why South Lake has no grade
We grade a lake only when its monitoring record clears the evidence bar: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For South Lake, the only measurement available is water clarity, which is not a water-quality indicator on its own — EPA's National Lakes Assessment does not grade clarity. Sampling here has recorded water clarity, but not phosphorus and algae (chlorophyll-a).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by MPCA and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
South Lake is a 1,145-acre lake in Cook County, Minnesota with a maximum depth of 140 feet. Overall water quality is improving over recent sampling years. The lake supports 6 documented fish species including brook trout, burbot, and lake trout. No public access — the lake is private or restricted.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-07-03. Grade methodology: LakeGrade methodology.
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Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for South Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Crystal clear, you can see 26 ft down. Trophic State Index: 30.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 26 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 30 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near South Lake
Compare lakeside cabins, hotels, and vacation rentals near South Lake in Cook 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 South Lake
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Planning a whole trip? See where to stay at Minnesota’s top lakes →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 140 ft |
| Surface Area | 1,145 acres |
| Shoreline Length | 15 mi |
| Littoral Zone | 15% |
| Public Access | No |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Fish Species
Click a species to see every graded lake where it is documented.
Fishing South Lake
DNR Fisheries Survey Summary
2 surveys on file from MN DNR Fisheries. Most recent: 2023-06-20 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| White Sucker | 10.09 | 2.16 lb |
| Tullibee (Cisco) | 5.56 | 0.19 lb |
| Lake Trout | 4.63 | 3.52 lb |
| Smallmouth Bass | 2.83 | 1.14 lb |
| BUB | 2.10 | 1.42 lb |
| Yellow Perch | 0.83 | 0.07 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.
White Sucker
Tullibee (Cisco)
Lake Trout
Smallmouth Bass
From the 2023-06-20 survey
South Lake lies on the Minnesota-Ontario border. The Minnesota side is entirely inside the BWCAW and has been non-motorized since 1978. There are no restrictions on motorized use on the Ontario side of the lake. Access is provided by portage trails from North, Topper, and Rose (via Rat) Lakes. Public access is…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for South Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — SouthFisheries Lake Survey · MN DNR LakeFinder
Water Quality Trend: ↑ Improving
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +2.98 m/yr | 2 |
EPA Impairment Status
South 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 MN16-0245-00 · Official waterbody report · Matched by proximity (2.5 km)
Graded lakes near South Lake
South Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Cook County
Frequently asked questions about South Lake
What is the water quality grade for South Lake?
- South Lake in Cook County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 26 ft visibility. Maximum depth: 140 ft. Surface area: 1144.75 acres.
Is South Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. South Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
How deep is South Lake?
- South Lake has a maximum depth of 140 feet. The lake covers 1144.75 acres.
What fish are in South Lake?
- Fish species found in South Lake include brook trout, burbot, lake trout, smallmouth bass, tullibee (cisco), white sucker. South Lake is located in Cook County, Minnesota.
Explore South Lake across LakeGrade
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Where this data comes from
3 measurements from 2 monitoring stations, 2023–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA3 samples · 2023–2025
Analytical methods
- Field measurement/observation, generic method
Monitoring station identifiers (2)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated 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