Dark Lake
Koochiching County, Minnesota120 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Dark Lake. Here is what has been measured.
- Eutrophic
- Impaired · Mercury
- 50 ft max depth
- Public access
- Limited data
Dark Lake in Koochiching County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 6.4 ft visibility. Phosphorus: 139.5 µg/L. Chlorophyll-a (algae): 5.8 µg/L. Maximum depth: 50 ft. Surface area: 119.61 acres.
Dark Lake is a 120-acre productive, nutrient-rich eutrophic lake in Koochiching County, Minnesota with a maximum depth of 50 feet. The lake supports 10 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 1 public boat landing. Compared to the 2 other monitored lakes in Koochiching County, Dark Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-02. Methodology: how these readings are compared.
What Dark Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
- Fishing10 species recorded
- Deep water50 ft surveyed max depth
Swimming conditions
Readings onlyLimited data
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. Dark Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether Dark 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 Dark Lake
These are the measurements Minnesota PCA publishes for Dark Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Murky, only visible to about 6.4 ft. Phosphorus 139.5 µg/L. Chlorophyll-a 5.8 µg/L. TSI 58.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 6.4ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 140µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 5.8µg/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. | 58 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Dark Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Dark Lake typically sits around 56°F at the surface in September. Summer average is about 55°F. Usually warmest in Aug (about 57°F) and coldest in Jun (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 (57°F).
Typical surface water temperature by month, from 48 field readings (2025–2025) via the EPA Water Quality Portal. See the full Dark Lake water temperature breakdown →
Lake Details
Max depth
50 ft
Surface area
120 acres
Shoreline
3.1 mi
Littoral zone
59%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
2 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,319 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Dark 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 Dark Lake
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Top-rated places to stay near Dark Lake
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Fish Species
Click a species to see every lake where it is documented.
Fishing Dark Lake
Reservoir Info (USACE NID)
Dark Lake is a man-made reservoir impounded by the Clear Dark Little Lakes (completed 1958), built primarily for other on the Lost River-TR; gravity-type dam, 7 ft tall and 12 ft long.
- Surface area
- 78 ac
- Normal storage
- 2,370 ac-ft
- Max storage
- 2,904 ac-ft
- Drainage area
- 3.1 sq mi
- Hazard class
- Low
- Owner
- MNDNR
Source: USACE National Inventory of Dams, NID ID MN00091 · Operator website · Matched by proximity (0.76 km)
EPA Impairment Status
Dark 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: Fish consumption.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN36-0014-00 · Official waterbody report
Nearby Lakes in Koochiching County
Frequently asked questions about Dark Lake
Where is Dark Lake?
- Dark Lake is a lake in Koochiching County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Dark Lake?
- Dark Lake in Koochiching County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 6.4 ft visibility. Phosphorus: 139.5 µg/L. Chlorophyll-a (algae): 5.8 µg/L. Maximum depth: 50 ft. Surface area: 119.61 acres.
Is Dark Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Dark Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
What is the water temperature of Dark Lake?
- Dark Lake typically sits around 56°F at the surface in September, from 48 EPA Water Quality Portal field readings (2025–2025). That is a typical value for the month, not a live reading.
How deep is Dark Lake?
- Dark Lake has a maximum depth of 50 feet. The lake covers 119.61 acres.
What fish are in Dark Lake?
- Fish species found in Dark Lake include black bullhead, black crappie, bluegill, brown bullhead, largemouth bass, northern pike, rock bass, walleye, white sucker, yellow perch. Dark Lake is located in Koochiching County, Minnesota.
Are there boat ramps on Dark Lake?
- Dark Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Dark Lake. Public access is listed as yes.
Can I fish at Dark Lake?
- Dark 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 Dark Lake across LakeQuality
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Where this data comes from
16 measurements from 1 monitoring station, 2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA16 samples · 2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by 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