Colby Lake
Washington County, Minnesota71 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Colby Lake. Here is what has been measured.
- Eutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- Eurasian watermilfoil
- 11 ft max depth
- Limited data
Colby Lake in Washington County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 3.8 ft visibility. Phosphorus: 61 µg/L. Chlorophyll-a (algae): 34.5 µg/L. Maximum depth: 11 ft. Surface area: 70.94 acres.
Colby Lake is a 71-acre productive, nutrient-rich eutrophic lake in Washington County, Minnesota with a maximum depth of 11 feet (7-foot average). The lake supports 8 documented fish species including black bullhead, black crappie, and bluegill. No public access — the lake is private or restricted. Compared to the 74 other monitored lakes in Washington County, Colby Lake ranks #66 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-10-22. Methodology: how these readings are compared.
Colby Lake covers about 71 acres in Washington County. For a place on the water, look through cabin and lake-house rentals near Colby Lake on Vrbo. For a hotel or motel room, Booking.com and Expedia both search around the lake.
What Colby Lake is good for
From access and monitoring records, not editorial picks.
- Fishing8 species recorded
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. Colby Lake is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Colby 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 Colby Lake
These are the measurements Minnesota PCA publishes for Colby 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 3.8 ft. Phosphorus 61 µg/L. Chlorophyll-a 34.5 µg/L. TSI 62.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 3.8ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 61µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 34.5µg/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. | 62 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Colby Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Colby Lake typically sits around 58°F at the surface in October. Summer average is about 73°F. Usually warmest in Jul (about 76°F) and coldest in Apr (about 54°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (54°F) to its warmest (76°F).
Typical surface water temperature by month, from 83 field readings (2011–2024) via the EPA Water Quality Portal. See the full Colby Lake water temperature breakdown →
Lake Details
Max depth
11 ft
Average depth
7 ft
Surface area
71 acres
Shoreline
2.3 mi
Littoral zone
97%
Share shallower than 15 ft
Public access
No
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
11 sq mi
HydroLAKES / HydroSHEDS
Elevation
886 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Stays via Stay22
Stays near Colby Lake
Compare lakeside cabins, hotels, and vacation rentals near Colby Lake in Washington 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 Colby Lake are listed below.
Top-rated places to stay near Colby 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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Fish Species
Click a species to see every lake where it is documented.
Fishing Colby Lake
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
EPA Impairment Status
Colby Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Recreation.
Source: EPA ATTAINS assessment unit MN82-0094-00 · Official waterbody report
Nearby Lakes in Washington County
Frequently asked questions about Colby Lake
Where is Colby Lake?
- Colby Lake is a lake in Washington County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Colby Lake?
- Colby Lake in Washington County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 3.8 ft visibility. Phosphorus: 61 µg/L. Chlorophyll-a (algae): 34.5 µg/L. Maximum depth: 11 ft. Surface area: 70.94 acres.
Is Colby Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Colby Lake is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Colby Lake?
- Colby Lake typically sits around 58°F at the surface in October, from 83 EPA Water Quality Portal field readings (2011–2024). That is a typical value for the month, not a live reading.
How deep is Colby Lake?
- Colby Lake has a maximum depth of 11 feet and an average depth of 7 feet. The lake covers 70.94 acres.
What fish are in Colby Lake?
- Fish species found in Colby Lake include black bullhead, black crappie, bluegill, channel catfish, green sunfish, hybrid sunfish, pumpkinseed, yellow perch. Colby Lake is located in Washington County, Minnesota.
Can I fish at Colby Lake?
- Public access to Colby 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 Colby Lake across LakeQuality
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Where this data comes from
56 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
MNPCA56 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