Long Lake
Otter Tail County, Minnesota395 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Long Lake. Here is what has been measured.
- Mesotrophic
- 88 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: 12.1 ft visibility. Phosphorus: 19.5 µg/L. Chlorophyll-a (algae): 5.3 µg/L. Maximum depth: 88 ft. Surface area: 395.42 acres.
Minnesota DNR's Targeted Survey on May 28, 2025 caught 146.22 largemouth bass per hour of electrofishing at Long Lake. Length samples in the latest survey that recorded them ran 3–16 inches. DNR survey details →
Long Lake is a 395-acre mesotrophic lake in Otter Tail County, Minnesota with a maximum depth of 88 feet. Phosphorus level is improving over recent sampling years. The lake supports 1 documented fish species including largemouth bass. Public access is available with 1 public boat landing. Compared to the 65 other monitored lakes in Otter Tail County, Long Lake ranks #5 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-16. Methodology: how these readings are compared.
What Long Lake is good for
From access and monitoring records, not editorial picks.
- Clear water12.1 ft of visibility
- Boat launch1 documented ramp
- Ice seasonIce-out around Apr 29
- Deep water88 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. 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.
Good clarity, visible to about 12.1 ft. Phosphorus 19.5 µg/L. Chlorophyll-a 5.3 µg/L. TSI 45.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 12.1ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 19.5µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 5.3µg/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. | 45 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Long Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Long Lake typically sits around 62°F at the surface in September. Summer average is about 73°F. Usually warmest in Jul (about 74°F) and coldest in May (about 58°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (58°F) to its warmest (74°F).
Typical surface water temperature by month, from 20 field readings (2011–2023) via the EPA Water Quality Portal.
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 (147,231 cells/mL) on November 22, 2025.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Minnesota DNR's Targeted Survey on May 28, 2025 caught 146.22 largemouth bass per hour of electrofishing at Long Lake. Length samples in the latest survey that recorded them ran 3–16 inches.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Long Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is stable. 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: 2025-05-28 (Targeted Survey).
7 surveys on file · most recent 2025-05-28 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Largemouth Bass | 55.12 | 3–16 in 2025-05-28 | 0.91 lb |
| Yellow Bullhead | 36.35 | 6–12 in 2012-07-30 | 0.58 lb |
| Bluegill | 23.96 | 3–8 in 2012-07-30 | 0.13 lb |
| Pumpkinseed | 5.01 | 3–6 in 2012-07-30 | 0.18 lb |
| Hybrid Sunfish | 5.00 | 3–8 in 2012-07-30 | 0.2 lb |
| Northern Pike | 4.35 | 12–29 in 2012-07-30 | 1.61 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.
Largemouth Bass
Yellow Bullhead
Bluegill
Pumpkinseed
From the 2025-05-28 survey
Long Lake is a 350-acre mesotrophic (moderately fertile) lake located in south-central Otter Tail County approximately five miles east of Dalton, MN. Long Lake is part of the Pomme de Terre River Watershed. There are no inlets or outlets connected to Long Lake. The immediate watershed is composed primarily of…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Long Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — LongFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Long (0942)Aquatic Plant Report · MN 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
88 ft
Surface area
395 acres
Shoreline
6.2 mi
Littoral zone
60%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
7 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,263 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Long 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 Long Lake
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Follow Long Lake’s readings
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Fish Species
Click a species to see every lake where it is documented.
Fishing Long Lake
Water Quality Trend: Stable
Based on 6 years of monitoring (2020–2025).
Water clarity
Stable6 years
Phosphorus
Improving-1.15 µg/L/yr5 years
Chlorophyll-a
Worsening+0.19 µg/L/yr5 years
Ice season
Typical ice-out
Apr 29
Earliest Apr 20, 2007 · Latest Apr 30, 2008
Typical ice-in
Nov 26
Earliest Nov 20, 2022 · Latest Dec 7, 2021
Most recent ice-out
Apr 29
2022
7 observations · Minnesota PCA ice records
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: 12.1 ft visibility. Phosphorus: 19.5 µg/L. Chlorophyll-a (algae): 5.3 µg/L. Maximum depth: 88 ft. Surface area: 395.42 acres.
Is Long Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Long Lake?
- Long Lake typically sits around 62°F at the surface in September, from 20 EPA Water Quality Portal field readings (2011–2023). That is a typical value for the month, not a live reading.
How deep is Long Lake?
- Long Lake has a maximum depth of 88 feet. The lake covers 395.42 acres.
What fish are in Long Lake?
- Fish species found in Long Lake include largemouth bass. Long Lake is located in Otter Tail County, Minnesota.
What did the DNR fisheries survey find at Long Lake?
- Minnesota DNR's Targeted Survey on May 28, 2025 caught 146.22 largemouth bass per hour of electrofishing at Long Lake. Length samples in the latest survey that recorded them ran 3–16 inches. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Long Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
When does Long Lake thaw?
- Long Lake typically has ice-out around Apr 29. Ice typically forms around Nov 26. The open water season is approximately 211 days.
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 (147,231 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 Long Lake. 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.
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Where this data comes from
79 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
MNPCA79 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
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