Long Lake
Otter Tail County, MinnesotaView mapDirections
Minnesota PCA publishes the water-quality measurements for Long Lake. Here is what has been measured.
- Eutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- 71 ft max depth
- Public access
Long Lake in Otter Tail County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 3 ft visibility. Phosphorus: 35 µg/L. Chlorophyll-a (algae): 16 µg/L.
Long Lake is a productive, nutrient-rich eutrophic lake in Otter Tail County, Minnesota with an estimated average depth of about 71 feet. Overall water quality is improving 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, Long Lake ranks #63 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-08-18. Methodology: how these readings are compared.
What Long Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
- Fishing13 species recorded
Swimming conditions
Readings onlyRecreation use not supported
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. Long Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Long 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 Long Lake
These are the measurements Minnesota PCA publishes for Long Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 3 ft of visibility. Phosphorus 35 µg/L. Chlorophyll-a 16 µg/L. TSI 58.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 3ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 35µg/L | Fair GoodFairPoor |
| Chlorophyll-a (algae) | 16µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 58 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Long Lake
Answers come straight from the public measurements and survey records on this page.
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Long Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was high (118,032 cells/mL) on July 18, 2026.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Long Lake. 2 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fish Stocking History — LongFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — LongPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
~71 ft est.
Public access
Yes
Listed by Minnesota PCA
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Minnesota has not published bathymetry for Long Lake.
Lake Size & Watershed
Watershed (drainage) area
6 sq mi
HydroLAKES / HydroSHEDS
Surface area
1,018 acres
HydroLAKES / HydroSHEDS
Shoreline
8.6 mi
HydroLAKES / HydroSHEDS
Elevation
1,309 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Recreation & Access
- Riviera (North)Public
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Long Lake
Compare lakeside cabins, hotels, and vacation rentals near Long 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. The water-quality readings cover nutrients and algae, not lodging. Cabins and rentals around Long Lake are listed below.
Top-rated places to stay near Long Lake
Prices for Oct 9–11, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
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 Long Lake
Water Quality Trend: Improving
Based on 6 years of monitoring (2020–2025).
Water clarity
Improving6 years
Phosphorus
Improving-7.01 µg/L/yr6 years
Chlorophyll-a
Improving-5.98 µg/L/yr6 years
EPA Impairment Status
Long 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: Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN56-0210-00 · Official waterbody report
Nearby Lakes in Otter Tail County
Frequently asked questions about Long Lake
Where is Long Lake?
- Long 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 Long Lake?
- Long Lake in Otter Tail County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 3 ft visibility. Phosphorus: 35 µg/L. Chlorophyll-a (algae): 16 µg/L.
Is Long Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Long Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
How deep is Long Lake?
- No published bathymetric survey covers Long Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 71 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
What fish are in Long Lake?
- Fish species found in Long Lake include black bullhead, black crappie, bluegill, brown bullhead, common carp, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, rock bass, walleye, white sucker, yellow bullhead. Long Lake is located in Otter Tail County, Minnesota.
Does Long Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Long Lake (clouds, ice, or an off-season gap). The most recent reading was high (118,032 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Are there boat ramps on Long Lake?
- Long Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Riviera (North). Public access is listed as yes.
Can I fish at Long Lake?
- Long 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 Long Lake across LakeQuality
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Where this data comes from
87 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
MNPCA87 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