South Twin Lake
South Twin Lake in Beltrami County, Minnesota has a water quality grade of A (Excellent). 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.
- Clarity
- 16.7 ft
- Typical in August
- 69°F
- Max depth
- 45 ft
- Area
- 222 acres
- Type
- Oligotrophic
- Trend
- ↓ Declining
- Public access
- Yes
- Ice-out
- May 8
Next lake in Beltrami County
South Twin Lake is a 222-acre cold, clear oligotrophic lake in Beltrami County, Minnesota with a maximum depth of 45 feet. Water quality is graded A based on 2 sampling years through 2025. 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. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLow algae
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A (Excellent)
Crystal clear, you can see 16.7 ft down. Phosphorus level: 8.5 µg/L. Chlorophyll-a: 2.2 µg/L. Trophic State Index: 37.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 16.7 ft | Not graded |
| Phosphorus | 8.5 µg/L | Good |
| Chlorophyll-a (Algae) | 2.2 µg/L | Good |
| Trophic State Index (TSI) | 37 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near South Twin Lake
Compare lakeside cabins, hotels, and vacation rentals near South Twin Lake in Beltrami 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.
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Water Temperature
South Twin Lake typically sits around 69°F at the surface in August. 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.
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 →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 45 ft |
| Surface Area | 222 acres |
| Shoreline Length | 3.1 mi |
| Littoral Zone | 34% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- South Twin LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing South Twin Lake
DNR Fisheries Survey Summary
8 surveys on file from MN DNR Fisheries. Most recent: 2025-06-30 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| MMS | 69.33 | — |
| Bluegill | 26.08 | 0.21 lb |
| Bluntnose Minnow | 23.52 | — |
| Yellow Perch | 14.85 | 0.24 lb |
| Largemouth Bass | 10.66 | 0.69 lb |
| BKF | 9.17 | — |
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
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
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.016 m/yr | 6 |
| Phosphorus | ↓ Declining | +0.44 µg/L/yr | 6 |
| Chlorophyll-a | → Stable | 0 µg/L/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (5 observations).
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2017-04-09 (2017) | 2022-05-08 (2022) |
| Ice-In | 2018-11-15 (2018) | 2007-11-29 (2007) |
Most recent ice-out: 2022-05-08
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
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN04-0053-00 · Official waterbody report
County Ranking
Ranked #48 of 85 lakes in Beltrami County
Nearby Lakes in Beltrami County
Frequently asked questions about South Twin Lake
What is the water quality grade for South Twin Lake?
- South Twin Lake in Beltrami County, Minnesota has a water quality grade of A (Excellent). 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?
- Excellent for swimming, crystal clear water with minimal algae. South Twin Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 2.2 µg/L. Always check local health department advisories before swimming.
What is the water temperature of South Twin Lake?
- South Twin Lake typically sits around 69°F at the surface in August, 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.
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.
Explore South Twin Lake across LakeGrade
Depth, room, public access, and the state wake-sport rules
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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)
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
Named boat-access points from the USGS National Boat Ramps inventory
Ice data from Minnesota DNR Climate