South Farm Lake
South Farm Lake in Lake County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 5 ft visibility. Maximum depth: 31 ft. Surface area: 563.98 acres.
- Clarity
- 5 ft
- Typical in August
- 68°F
- Max depth
- 31 ft
- Area
- 564 acres
- Trend
- → Stable
- Public access
- No
Next lake in Lake County
Why South Farm 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 Farm 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 Farm Lake is a 564-acre lake in Lake County, Minnesota with a maximum depth of 31 feet. Water clarity is declining over recent sampling years. The lake supports 11 documented fish species including black crappie, bluegill, and burbot. No public access — the lake is private or restricted.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-29. 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 Farm Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Murky, only visible to about 5 ft. Trophic State Index: 54.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 5 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 54 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near South Farm Lake
Compare lakeside cabins, hotels, and vacation rentals near South Farm Lake in Lake 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 Farm Lake
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Water Temperature
South Farm Lake typically sits around 68°F at the surface in August. Summer average is about 66°F. Usually warmest in Aug (about 68°F) and coldest in May (about 55°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 69 field readings (2023–2025) via the EPA Water Quality Portal. See the full South Farm Lake water temperature breakdown →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for South Farm Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was high (731,139 cells/mL) on May 30, 2026.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 31 ft |
| Surface Area | 564 acres |
| Shoreline Length | 10.8 mi |
| Littoral Zone | 64% |
| 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 Farm Lake
DNR Fisheries Survey Summary
13 surveys on file from MN DNR Fisheries. Most recent: 2025-07-31 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| CIS | 21.50 | 0.25 lb |
| Tullibee (Cisco) | 14.63 | 0.38 lb |
| Bluegill | 5.25 | 0.21 lb |
| Yellow Perch | 4.04 | 0.16 lb |
| White Sucker | 2.66 | 2.22 lb |
| Walleye | 2.24 | 1.19 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.
CIS
Tullibee (Cisco)
Bluegill
Yellow Perch
From the 2025-07-31 survey
Temperature and dissolved oxygen measurements were collected from the deepest basin in South Farm Lake on July 31st, 2025. This was done to evaluate the quantity and quality of cold, oxygenated water (i.e., oxythermal habitat) available to Cisco, also known as Tullibee, the most sensitive coldwater species present in…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for South Farm Lake. 2 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — South FarmFisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — South FarmFish Stocking History · MN DNR LakeFinder
Water Quality Trend: → Stable
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.047 m/yr | 6 |
| Phosphorus | → Stable | +0.19 µg/L/yr | 6 |
| Chlorophyll-a | ↑ Improving | -0.15 µg/L/yr | 6 |
EPA Impairment Status
South Farm Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit MN38-0778-00 · Official waterbody report
Graded lakes near South Farm Lake
South Farm Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Lake County
Frequently asked questions about South Farm Lake
What is the water quality grade for South Farm Lake?
- South Farm Lake in Lake County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 5 ft visibility. Maximum depth: 31 ft. Surface area: 563.98 acres.
Is South Farm Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. South Farm Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
What is the water temperature of South Farm Lake?
- South Farm Lake typically sits around 68°F at the surface in August, from 69 EPA Water Quality Portal field readings (2023–2025). That is a typical value for the month, not a live reading.
How deep is South Farm Lake?
- South Farm Lake has a maximum depth of 31 feet. The lake covers 563.98 acres.
What fish are in South Farm Lake?
- Fish species found in South Farm Lake include black crappie, bluegill, burbot, cisco species, northern pike, rock bass, smallmouth bass, tullibee (cisco), walleye, white sucker, yellow perch. South Farm Lake is located in Lake County, Minnesota.
Does South Farm Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for South Farm Lake (clouds, ice, or an off-season gap). The most recent reading was high (731,139 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Explore South Farm Lake across LakeGrade
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Where this data comes from
85 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA85 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
Monitoring station identifiers (1)
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