Onagon Lake
Cook County, Minnesota31 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Onagon Lake. Here is what has been measured.
- 15 ft max depth
- Public access
- Limited data
Onagon Lake in Cook County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 6 ft visibility. Maximum depth: 15 ft. Surface area: 31.26 acres.
Minnesota DNR's Standard Survey on September 1, 1972 caught 9.33 northern pike per gill net at Onagon Lake. DNR survey details →
Onagon Lake is a 31-acre lake in Cook County, Minnesota with a maximum depth of 15 feet. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-10-03. Methodology: how these readings are compared.
What Onagon Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Onagon 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 Onagon Lake
These are the measurements Minnesota PCA publishes for Onagon 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 ft. TSI 51.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 6ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | No reading The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. | |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 51 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Onagon Lake
Answers come straight from the public measurements and survey records on this page.
Minnesota DNR's Standard Survey on September 1, 1972 caught 9.33 northern pike per gill net at Onagon Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Onagon Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
1 survey on file from MN DNR Fisheries. Most recent: 1972-09-01 (Standard Survey).
1 survey on file · most recent 1972-09-01 (Standard Survey)
54 years old| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Yellow Perch | 13.33 | 0.35 lb | |
| Northern Pike | 9.33 | 1.32 lb |
CPUE = catch per unit effort, fish caught per net per set in a standardised survey. It measures abundance, not size, and is not a weekly bite report.
From the 1972-09-01 survey
Ambush Lk has a large N Pike population with a good distribution of sizes. A forage species. Yel Perch are abundant with a good proportion of angling size, 10-12 inches.
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Onagon Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — AmbushFisheries Lake Survey · MN DNR LakeFinder
Lake Details
Max depth
15 ft
Surface area
31 acres
Shoreline
1.4 mi
Littoral zone
100%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Recreation & Access
- SaganagaPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Onagon Lake
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Top-rated places to stay near Onagon Lake
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Follow Onagon Lake’s readings
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Fishing Onagon Lake
Water Quality Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Water clarity
Worsening6 years
Phosphorus
Worsening+0.2 µg/L/yr5 years
Chlorophyll-a
Worsening+0.35 µg/L/yr5 years
Nearby Lakes in Cook County
Frequently asked questions about Onagon Lake
Where is Onagon Lake?
- Onagon Lake is a lake in Cook County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Onagon Lake?
- Onagon Lake in Cook County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 6 ft visibility. Maximum depth: 15 ft. Surface area: 31.26 acres.
Is Onagon Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
How deep is Onagon Lake?
- Onagon Lake has a maximum depth of 15 feet. The lake covers 31.26 acres.
What did the DNR fisheries survey find at Onagon Lake?
- Minnesota DNR's Standard Survey on September 1, 1972 caught 9.33 northern pike per gill net at Onagon Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Onagon Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
Are there boat ramps on Onagon Lake?
- Onagon Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Saganaga. Public access is listed as yes.
Can I fish at Onagon Lake?
- Onagon 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 Onagon Lake across LakeQuality
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Where this data comes from
26 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
MNPCA26 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
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
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory