Triangle Lake
Lake County, Minnesota300 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Triangle Lake. Here is what has been measured.
- Impaired · Mercury
- 43 ft max depth
- Limited data
Triangle Lake in Lake County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 12.3 ft visibility. Phosphorus: 7 µg/L. Chlorophyll-a (algae): 2.1 µg/L. Maximum depth: 43 ft. Surface area: 299.89 acres.
Minnesota DNR's Standard Survey on July 20, 2020 caught 9.89 walleye per gill net at Triangle Lake. Length samples in the latest survey that recorded them ran 7–28 inches. DNR survey details →
Triangle Lake is a 300-acre lake in Lake County, Minnesota with a maximum depth of 43 feet (15-foot average). The lake supports 7 documented fish species including cisco species, northern pike, and rock bass. No public access — the lake is private or restricted.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2022-07-18. Methodology: how these readings are compared.
What Triangle Lake is good for
From access and monitoring records, not editorial picks.
- Clear water12.3 ft of visibility
- Fishing7 species recorded
- Ice seasonIce-out around Apr 25
- Deep water43 ft surveyed max depth
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Triangle Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether Triangle 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 Triangle Lake
These are the measurements Minnesota PCA publishes for Triangle Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Good clarity, visible to about 12.3 ft. Phosphorus 7 µg/L. Chlorophyll-a 2.1 µg/L. TSI 37.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 12.3ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 7µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | 2.1µg/L | Measured, not scored 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. | 37 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Triangle Lake
Answers come straight from the public measurements and survey records on this page.
Minnesota DNR's Standard Survey on July 20, 2020 caught 9.89 walleye per gill net at Triangle Lake. Length samples in the latest survey that recorded them ran 7–28 inches.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Triangle Lake’s water-quality measurements separately. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
11 surveys on file from MN DNR Fisheries. Most recent: 2020-07-20 (Standard Survey).
11 surveys on file · most recent 2020-07-20 (Standard Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Yellow Perch | 5.65 | 4–8 in 2020-07-20 | 0.15 lb |
| Tullibee (Cisco) | 5.38 | 8–16 in 2014-07-28 | 1.38 lb |
| Walleye | 4.60 | 7–28 in 2020-07-20 | 2.19 lb |
| Rock Bass | 2.76 | 4–7 in 2020-07-20 | 0.18 lb |
| Northern Pike | 2.09 | 11–38 in 2020-07-20 | 2.92 lb |
| White Sucker | 1.81 | 10–23 in 2020-07-20 | 3.11 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.
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.
Yellow Perch
Tullibee (Cisco)
Walleye
Rock Bass
From the 2020-07-20 survey
Triangle Lake is located 13 miles east of Ely. There are two "remote" public accesses. The most commonly used access is a 50 yard roller portage between the southern shore of Ojibway Lake and the northern shore of Triangle Lake. The portage is slightly uphill to Triangle but boats up to 16 feet long are able to be…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Triangle Lake. 2 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — TriangleFisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — TriangleFish Stocking History · MN DNR LakeFinder
Lake Details
Max depth
43 ft
Average depth
14.5 ft
Surface area
300 acres
Shoreline
10.4 mi
Littoral zone
53%
Share shallower than 15 ft
Public access
No
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
4 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,483 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
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Stays near Triangle Lake
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Follow Triangle Lake’s readings
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Fish Species
Click a species to see every lake where it is documented.
Fishing Triangle Lake
Ice season
Typical ice-out
Apr 25
Earliest Apr 22, 1999 · Latest Apr 29, 1997
Most recent ice-out
Apr 22
1999
3 observations · Minnesota PCA ice records
EPA Impairment Status
Triangle 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 MN38-0715-00 · Official waterbody report
Nearby Lakes in Lake County
Frequently asked questions about Triangle Lake
Where is Triangle Lake?
- Triangle Lake is a lake in Lake County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Triangle Lake?
- Triangle Lake in Lake County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 12.3 ft visibility. Phosphorus: 7 µg/L. Chlorophyll-a (algae): 2.1 µg/L. Maximum depth: 43 ft. Surface area: 299.89 acres.
Is Triangle Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Triangle Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
How deep is Triangle Lake?
- Triangle Lake has a maximum depth of 43 feet and an average depth of 14.5 feet. The lake covers 299.89 acres.
What fish are in Triangle Lake?
- Fish species found in Triangle Lake include cisco species, northern pike, rock bass, smallmouth bass, walleye, white sucker, yellow perch. Triangle Lake is located in Lake County, Minnesota.
What did the DNR fisheries survey find at Triangle Lake?
- Minnesota DNR's Standard Survey on July 20, 2020 caught 9.89 walleye per gill net at Triangle Lake. Length samples in the latest survey that recorded them ran 7–28 inches. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Triangle Lake’s water-quality measurements separately. Catch rate is not a swim clearance and is not a weekly bite report.
When does Triangle Lake thaw?
- Triangle Lake typically has ice-out around Apr 25.
Can I fish at Triangle Lake?
- Public access to Triangle 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 Triangle Lake across LakeQuality
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Where this data comes from
5 measurements from 1 monitoring station, 2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA5 samples · 2022
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- 2130 B ~ Nephelometric Method
- 2120 B ~ Color in Water by Visual Comparison
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
Ice data from Minnesota DNR Climate