South Twin Lake
Beltrami County, Minnesota222 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for South Twin Lake. Here is what has been measured.
- Oligotrophic
- Impaired · Mercury
- 45 ft max depth
- Public access
South Twin Lake in Beltrami County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 16.7 ft visibility. Phosphorus: 8.5 µg/L. Chlorophyll-a (algae): 2.2 µg/L. Maximum depth: 45 ft. Surface area: 221.54 acres.
Minnesota DNR's Targeted Survey on June 30, 2025 caught 0.44 walleye per trap net at South Twin Lake. DNR survey details →
South Twin Lake is a 222-acre cold, clear oligotrophic lake in Beltrami County, Minnesota with a maximum depth of 45 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 84 other monitored lakes in Beltrami County, South Twin Lake ranks #48 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-22. Methodology: how these readings are compared.
What South Twin Lake is good for
From access and monitoring records, not editorial picks.
- Clear water16.7 ft of visibility
- Boat launch1 documented ramp
- Fishing11 species recorded
- Ice seasonIce-out around May 8
- Deep water45 ft surveyed max depth
Swimming conditions
Readings onlyLow algae
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. South Twin Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether South Twin 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 South Twin Lake
These are the measurements Minnesota PCA publishes for South Twin Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Crystal clear, you can see 16.7 ft down. Phosphorus 8.5 µg/L. Chlorophyll-a 2.2 µg/L. TSI 37.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 16.7ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 8.5µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 2.2µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 37 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about South Twin Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
South Twin Lake typically sits around 69°F at the surface in September. Summer average is about 71°F. Usually warmest in Jul (about 78°F) and coldest in Jun (about 67°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (67°F) to its warmest (78°F).
Typical surface water temperature by month, from 16 field readings (2016–2021) via the EPA Water Quality Portal. See the full South Twin Lake water temperature breakdown →
Minnesota DNR's Targeted Survey on June 30, 2025 caught 0.44 walleye per trap net at South Twin Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows South Twin Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
8 surveys on file from MN DNR Fisheries. Most recent: 2025-06-30 (Targeted Survey).
8 surveys on file · most recent 2025-06-30 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluegill | 26.08 | 3–10 in 2025-06-30 | 0.21 lb |
| Bluntnose Minnow | 23.52 | ||
| Yellow Perch | 14.85 | 9 in 2025-06-30 | 0.24 lb |
| Largemouth Bass | 10.66 | 5–13 in 2025-06-30 | 0.69 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
Yellow Perch
Largemouth Bass
From the 2025-06-30 survey
A targeted survey of nearshore fish species in South Twin Lake, was conducted on June 30th and July 1st, 2025, by Lake Biological Monitoring and Assessment (LBMA) Program staff. Sampling sites were evenly spaced around the lake, and each was sampled by backpack electrofishing and seining with a 50-foot or 15-foot…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for South Twin Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — South TwinFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — South Twin (1759)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — South TwinFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — South TwinPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
45 ft
Surface area
222 acres
Shoreline
3.1 mi
Littoral zone
34%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
2 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,325 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- South Twin 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 South Twin Lake
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Top-rated places to stay near South Twin Lake
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Follow South Twin Lake’s readings
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Fish Species
Click a species to see every lake where it is documented.
Fishing South Twin Lake
Water Quality Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Water clarity
Stable6 years
Phosphorus
Worsening+0.44 µg/L/yr6 years
Chlorophyll-a
Stable0 µg/L/yr6 years
Ice season
Typical ice-out
May 8
Earliest Apr 9, 2017 · Latest May 8, 2022
Most recent ice-out
May 8
2022
5 observations · Minnesota PCA ice records
EPA Impairment Status
South Twin 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 MN04-0053-00 · Official waterbody report
Nearby Lakes in Beltrami County
Frequently asked questions about South Twin Lake
Where is South Twin Lake?
- South Twin Lake is a lake in Beltrami County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of South Twin Lake?
- South Twin Lake in Beltrami County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 16.7 ft visibility. Phosphorus: 8.5 µg/L. Chlorophyll-a (algae): 2.2 µg/L. Maximum depth: 45 ft. Surface area: 221.54 acres.
Is South Twin Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. South Twin 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 South Twin Lake?
- South Twin Lake typically sits around 69°F at the surface in September, from 16 EPA Water Quality Portal field readings (2016–2021). That is a typical value for the month, not a live reading.
How deep is South Twin Lake?
- South Twin Lake has a maximum depth of 45 feet. The lake covers 221.54 acres.
What fish are in South Twin Lake?
- Fish species found in South Twin Lake include black bullhead, black crappie, bluegill, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, rock bass, walleye, white sucker, yellow perch. South Twin Lake is located in Beltrami County, Minnesota.
What did the DNR fisheries survey find at South Twin Lake?
- Minnesota DNR's Targeted Survey on June 30, 2025 caught 0.44 walleye per trap net at South Twin Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows South Twin Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
When does South Twin Lake thaw?
- South Twin Lake typically has ice-out around May 8.
Are there boat ramps on South Twin Lake?
- South Twin Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include South Twin Lake. Public access is listed as yes.
Can I fish at South Twin Lake?
- South Twin 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 South Twin Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
Fish species and the cleanest lakes across Minnesota
Fish species and best lakes in Beltrami County
Species activity outlook by water temperature and season
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Where this data comes from
73 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
MNPCA73 samples · 2020–2025
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
Ice data from Minnesota DNR Climate