Long Lake
Dakota County, MinnesotaView mapDirections
Minnesota PCA publishes the water-quality measurements for Long Lake. Here is what has been measured.
- Hypereutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- 24 ft max depth
- Limited data
Long Lake in Dakota County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 1.6 ft visibility. Phosphorus: 110 µg/L. Chlorophyll-a (algae): 81.5 µg/L.
Long Lake is a highly nutrient-loaded hypereutrophic lake in Dakota County, Minnesota with an estimated average depth of about 24 feet. Limited fish-species data available. No public access — the lake is private or restricted. Compared to the 44 other monitored lakes in Dakota County, Long Lake ranks #33 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-10-17. Methodology: how these readings are compared.
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 1.6 ft of visibility. Phosphorus 110 µg/L. Chlorophyll-a 81.5 µg/L. TSI 72.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 1.6ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 110µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 81.5µg/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. | 72 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about Long Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Long Lake typically sits around 58°F at the surface in October. Summer average is about 77°F. Usually warmest in Jul (about 83°F) and coldest in Apr (about 51°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (51°F) to its warmest (83°F).
Typical surface water temperature by month, from 42 field readings (2010–2024) via the EPA Water Quality Portal. See the full Long Lake water temperature breakdown →
Lake Details
Max depth
~24 ft est.
Public access
No
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
2 sq mi
HydroLAKES / HydroSHEDS
Surface area
25 acres
HydroLAKES / HydroSHEDS
Shoreline
1 mi
HydroLAKES / HydroSHEDS
Elevation
896 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.
Stays via Stay22
Stays near Long Lake
Compare lakeside cabins, hotels, and vacation rentals near Long Lake in Dakota 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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Fishing Long Lake
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 MN19-0022-00 · Official waterbody report
Nearby Lakes in Dakota County
Frequently asked questions about Long Lake
Where is Long Lake?
- Long Lake is a lake in Dakota 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 Dakota County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 1.6 ft visibility. Phosphorus: 110 µg/L. Chlorophyll-a (algae): 81.5 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.
What is the water temperature of Long Lake?
- Long Lake typically sits around 58°F at the surface in October, from 42 EPA Water Quality Portal field readings (2010–2024). That is a typical value for the month, not a live reading.
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 24 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Can I fish at Long Lake?
- Public access to Long Lake is listed as no on the lake record, so confirm before you make the trip. 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
44 measurements from 1 monitoring station, 2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA44 samples · 2024
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Colorimetry
- Analysis of Chlorophyll in Periphyton and Plankton
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