Long Lake
Long Lake in Aitkin County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 10.8 ft visibility. Maximum depth: 116 ft. Surface area: 434.72 acres.
- Clarity
- 10.8 ft
- Typical in August
- 52°F
- Max depth
- 116 ft
- Area
- 435 acres
- Trend
- → Stable
- Public access
- Yes
- Ice-out
- Apr 18
- Open water
- 230 days
Next lake in Aitkin County
Why Long Lake has no grade
We grade a lake only when its monitoring record clears the evidence bar: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Long Lake, the only measurement available is water clarity, which is not a water-quality indicator on its own — EPA's National Lakes Assessment does not grade clarity. Sampling here has recorded water clarity, but not phosphorus and algae (chlorophyll-a).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by MPCA and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Long Lake is a 435-acre lake in Aitkin County, Minnesota with a maximum depth of 116 feet (30-foot average). The lake supports 16 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-28. Grade methodology: LakeGrade methodology.
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Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Long Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Good clarity, visible to about 10.8 ft. Trophic State Index: 43.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 10.8 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 43 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Long Lake
Compare lakeside cabins, hotels, and vacation rentals near Long Lake in Aitkin 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 Long Lake
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Water Temperature
Long Lake typically sits around 52°F at the surface in August. Summer average is about 51°F. Usually warmest in Aug (about 52°F) and coldest in May (about 47°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 460 field readings (2016–2025) via the EPA Water Quality Portal. See the full Long Lake water temperature breakdown →
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 (108,643 cells/mL) on November 29, 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 | 116 ft |
| Average Depth | 30 ft |
| Surface Area | 435 acres |
| Shoreline Length | 5.5 mi |
| Littoral Zone | 28% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Long LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Long Lake
DNR Fisheries Survey Summary
26 surveys on file from MN DNR Fisheries. Most recent: 2025-08-04 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Bluegill | 32.36 | 0.16 lb |
| Tullibee (Cisco) | 26.16 | 0.23 lb |
| Largemouth Bass | 15.33 | 0.91 lb |
| Bluntnose Minnow | 14.06 | — |
| BKS | 7.49 | — |
| BNS | 5.03 | — |
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
Tullibee (Cisco)
Largemouth Bass
From the 2025-08-04 survey
A temperature-dissolved oxygen (TDO) profile was collected on 8/4/2025, to measure the amount of thermal habitat available for Tullibee. Adequate oxy-thermal habitat for Tullibee survival was observed from a depth of 13 feet to approximately 106 feet. In some years, a TDO3 (temperature at 3 mg/l dissolved oxygen)…
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 (0029)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 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.003 m/yr | 5 |
Ice Season
Historical ice data from Minnesota DNR (19 observations).
Estimated open water season: 230 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2004-03-16 (2004) | 2008-04-30 (2008) |
| Ice-In | 2003-11-25 (2003) | 2007-12-16 (2007) |
Most recent ice-out: 2015-04-12
EPA Impairment Status
Long Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit MN01-0089-00 · Official waterbody report
Graded lakes near Long Lake
Long Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Aitkin County
Frequently asked questions about Long Lake
What is the water quality grade for Long Lake?
- Long Lake in Aitkin County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 10.8 ft visibility. Maximum depth: 116 ft. Surface area: 434.72 acres.
Is Long Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Long Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
What is the water temperature of Long Lake?
- Long Lake typically sits around 52°F at the surface in August, from 460 EPA Water Quality Portal field readings (2016–2025). That is a typical value for the month, not a live reading.
How deep is Long Lake?
- Long Lake has a maximum depth of 116 feet and an average depth of 30 feet. The lake covers 434.72 acres.
What fish are in Long Lake?
- Fish species found in Long Lake include black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, rock bass, splake, tullibee (cisco), walleye, white sucker, yellow bullhead, yellow perch. Long Lake is located in Aitkin County, Minnesota.
When does Long Lake thaw?
- Long Lake typically has ice-out around Apr 18. Ice typically forms around Dec 4. The open water season is approximately 230 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 (108,643 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.
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Where this data comes from
32 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
MNPCA32 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
Monitoring station identifiers (2)
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