Long Lake
Long Lake in Otter Tail County, Minnesota has a water quality grade of A (Excellent). 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.
- Clarity
- 12.1 ft
- Typical in August
- 71°F
- Max depth
- 88 ft
- Area
- 395 acres
- Type
- Mesotrophic
- Trend
- → Stable
- Public access
- Yes
- Ice-out
- Apr 29
- Open water
- 211 days
Next lake in Otter Tail County
Long Lake is a 395-acre mesotrophic lake in Otter Tail County, Minnesota with a maximum depth of 88 feet. Water quality is graded A based on 2 sampling years through 2025. Phosphorus level is improving over recent sampling years. The lake supports 1 documented fish species including largemouth bass. Public access is available with 2 public boat landings. 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. 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)
Good clarity, visible to about 12.1 ft. Phosphorus level: 19.5 µg/L. Chlorophyll-a: 5.3 µg/L. Trophic State Index: 45.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 12.1 ft | Not graded |
| Phosphorus | 19.5 µg/L | Good |
| Chlorophyll-a (Algae) | 5.3 µg/L | Good |
| Trophic State Index (TSI) | 45 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay 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.
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Water Temperature
Long Lake typically sits around 71°F at the surface in August. 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.
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 ↗
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 88 ft |
| Surface Area | 395 acres |
| Shoreline Length | 6.2 mi |
| Littoral Zone | 60% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Stalker LakePublic
- Long LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Long Lake
DNR Fisheries Survey Summary
7 surveys on file from MN DNR Fisheries. Most recent: 2025-05-28 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Largemouth Bass | 55.12 | 0.91 lb |
| Yellow Bass | 36.35 | 0.58 lb |
| Bluegill | 23.96 | 0.13 lb |
| Pumpkinseed | 5.01 | 0.18 lb |
| Hybrid Sunfish | 5.00 | 0.2 lb |
| Northern Pike | 4.35 | 1.61 lb |
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.
Largemouth Bass
Yellow Bass
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
Water Quality Trend: → Stable
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.034 m/yr | 6 |
| Phosphorus | ↑ Improving | -1.15 µg/L/yr | 5 |
| Chlorophyll-a | ↓ Declining | +0.19 µg/L/yr | 5 |
Ice Season
Historical ice data from Minnesota DNR (7 observations).
Estimated open water season: 211 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2007-04-20 (2007) | 2008-04-30 (2008) |
| Ice-In | 2022-11-20 (2022) | 2021-12-07 (2021) |
Most recent ice-out: 2022-04-29
County Ranking
Ranked #5 of 66 lakes in Otter Tail County
Nearby Lakes in Otter Tail County
Frequently asked questions about Long Lake
What is the water quality grade for Long Lake?
- Long Lake in Otter Tail County, Minnesota has a water quality grade of A (Excellent). 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?
- Excellent for swimming, crystal clear water with minimal algae. Long Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 5.3 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Long Lake?
- Long Lake typically sits around 71°F at the surface in August, 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.
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 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Stalker Lake, Long Lake. Public access is listed as yes.
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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)
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
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