South Turtle Lake
Otter Tail County, Minnesota837 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for South Turtle Lake. Here is what has been measured.
- Mesotrophic
- Impaired · Impaired biota (cause unknown)
- 35 ft max depth
- Public access
South Turtle Lake in Otter Tail County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 14.1 ft visibility. Phosphorus: 20 µg/L. Chlorophyll-a (algae): 3.7 µg/L. Maximum depth: 35 ft. Surface area: 836.57 acres.
Minnesota DNR's Targeted Survey on July 24, 2018 caught 5.44 largemouth bass per hour of electrofishing at South Turtle Lake. DNR survey details →
Free interactive depth-contour map of South Turtle Lake, reaching a maximum surveyed depth of 30 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Minnesota DNR.
South Turtle Lake is a 837-acre mesotrophic lake in Otter Tail County, Minnesota with a maximum depth of 35 feet. Overall water quality is declining over recent sampling years. The lake supports 13 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 1 public boat landing. Compared to the 65 other monitored lakes in Otter Tail County, South Turtle Lake ranks #33 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-22. Methodology: how these readings are compared.
South Turtle Lake covers about 840 acres in Otter Tail County. It has one public boat landing. The median ice-out date is April 20, which is when the open-water season begins. Vrbo is where to look for cabins and lake homes around South Turtle Lake, and Booking.com and Expedia search hotels near the lake for your dates.
What South Turtle Lake is good for
From access and monitoring records, not editorial picks.
- Clear water14.1 ft of visibility
- Boat launch1 documented ramp
- Fishing13 species recorded
- Ice seasonIce-out around Apr 20
- Deep water35 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 Turtle Lake is listed impaired under Clean Water Act §303(d) (IR 5) for impaired biota (cause unknown), mercury. Check local advisories before you swim.
Whether South Turtle 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 Turtle Lake
These are the measurements Minnesota PCA publishes for South Turtle Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Good clarity, visible to about 14.1 ft. Phosphorus 20 µg/L. Chlorophyll-a 3.7 µg/L. TSI 43.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 14.1ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 20µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 3.7µg/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. | 43 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about South Turtle Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
South Turtle Lake typically sits around 65°F at the surface in September. Summer average is about 73°F. Usually warmest in Jul (about 77°F) and coldest in May (about 56°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (56°F) to its warmest (77°F).
Typical surface water temperature by month, from 33 field readings (2010–2025) via the EPA Water Quality Portal. See the full South Turtle Lake water temperature breakdown →
Minnesota DNR's Targeted Survey on July 24, 2018 caught 5.44 largemouth bass per hour of electrofishing at South Turtle Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows South Turtle 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
7 surveys on file from MN DNR Fisheries. Most recent: 2018-07-24 (Targeted Survey).
7 surveys on file · most recent 2018-07-24 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluegill | 37.96 | 3–8 in 2017-08-28 | 0.16 lb |
| Yellow Bullhead | 16.56 | 5–13 in 2017-08-28 | 0.5 lb |
| Bluntnose Minnow | 12.53 | ||
| Green Sunfish | 12.13 | 2 in 2011-08-08 | 0.01 lb |
| Black Bullhead | 8.92 | 8–13 in 2017-08-28 | 0.44 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 Bullhead
Green Sunfish
Black Bullhead
From the 2018-07-24 survey
A targeted survey of the nearshore fish community in South Turtle Lake was conducted by Fisheries Index of Biological Integrity (IBI) Program Staff starting July 24, 2018 on South Turtle Lake. Fourteen sampling sites were evenly spaced around the lake and each was sampled by backpack electrofishing and seining with a…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for South Turtle 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 TurtleFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — South Turtle (1189)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — South TurtleFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — South TurtlePublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
35 ft
Surface area
837 acres
Shoreline
11 mi
Littoral zone
48%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
2 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,306 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- South Turtle 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 Turtle Lake
Compare lakeside cabins, hotels, and vacation rentals near South Turtle Lake in Otter Tail 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 Turtle Lake
Prices for Oct 9–11, 4 adults. Change dates on the map below.
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Planning a whole trip? See where to stay at Minnesota’s top lakes →
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Fish Species
Click a species to see every lake where it is documented.
Fishing South Turtle Lake
- → South Turtle Lake fishing: DNR survey catch rates, species & stocking
- → South Turtle Lake fishing forecast & best times (species outlook + 14-day solunar calendar)
- → South Turtle Lake fishing regulations (limits, seasons, special rules)
- → Is it safe to eat fish from South Turtle Lake? (mercury & PFAS guide)
Water Quality Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Water clarity
Stable6 years
Phosphorus
Stable-0.2 µg/L/yr6 years
Chlorophyll-a
Worsening+0.13 µg/L/yr6 years
Ice season
Typical ice-out
Apr 20
Earliest Mar 5, 2024 · Latest May 11, 2013
Typical ice-in
Nov 26
Earliest Nov 13, 2018 · Latest Dec 12, 2017
Most recent ice-out
Mar 5
2024
16 observations · Minnesota PCA ice records
EPA Impairment Status
South Turtle Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Aquatic life, Fish consumption.
Source: EPA ATTAINS assessment unit MN56-0377-00 · Official waterbody report
Nearby Lakes in Otter Tail County
Frequently asked questions about South Turtle Lake
Where is South Turtle Lake?
- South Turtle Lake is a lake in Otter Tail 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 Turtle Lake?
- South Turtle Lake in Otter Tail County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 14.1 ft visibility. Phosphorus: 20 µg/L. Chlorophyll-a (algae): 3.7 µg/L. Maximum depth: 35 ft. Surface area: 836.57 acres.
Is South Turtle Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. South Turtle Lake is listed impaired under Clean Water Act §303(d) (IR 5) for impaired biota (cause unknown), mercury. Check local advisories before you swim.
What is the water temperature of South Turtle Lake?
- South Turtle Lake typically sits around 65°F at the surface in September, from 33 EPA Water Quality Portal field readings (2010–2025). That is a typical value for the month, not a live reading.
How deep is South Turtle Lake?
- South Turtle Lake has a maximum depth of 35 feet. The lake covers 836.57 acres.
What fish are in South Turtle Lake?
- Fish species found in South Turtle Lake include black bullhead, black crappie, bluegill, brown bullhead, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, walleye, white sucker, yellow bullhead, yellow perch. South Turtle Lake is located in Otter Tail County, Minnesota.
What did the DNR fisheries survey find at South Turtle Lake?
- Minnesota DNR's Targeted Survey on July 24, 2018 caught 5.44 largemouth bass per hour of electrofishing at South Turtle Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows South Turtle 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 Turtle Lake thaw?
- South Turtle Lake typically has ice-out around Apr 20. Ice typically forms around Nov 26. The open water season is approximately 220 days.
Are there boat ramps on South Turtle Lake?
- South Turtle Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include South Turtle Lake. Public access is listed as yes.
Can I fish at South Turtle Lake?
- South Turtle 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 Turtle Lake across LakeQuality
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Where this data comes from
188 measurements from 2 monitoring stations, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA188 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 (2)
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