Triangle Lake
Triangle Lake in Lake County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. 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.
- Clarity
- 12.3 ft
- Max depth
- 43 ft
- Area
- 300 acres
- Public access
- No
- Ice-out
- Apr 25
Next lake in Lake County
Why Triangle Lake has no grade
We grade a lake only when its monitoring record clears the evidence bar: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Triangle Lake, no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). Sampling here has recorded water clarity, phosphorus and algae (chlorophyll-a).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by MPCA and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
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. Grade methodology: LakeGrade methodology.
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Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Triangle Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Good clarity, visible to about 12.3 ft. Phosphorus level: 7 µg/L. Chlorophyll-a: 2.1 µg/L. Trophic State Index: 37.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 12.3 ft | Not graded |
| Phosphorus | 7 µg/L | Not graded |
| Chlorophyll-a (Algae) | 2.1 µg/L | Not graded |
| Trophic State Index (TSI) | 37 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Triangle Lake
Compare lakeside cabins, hotels, and vacation rentals near Triangle Lake in Lake 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.
Top-rated places to stay near Triangle Lake
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Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 43 ft |
| Average Depth | 14.5 ft |
| Surface Area | 300 acres |
| Shoreline Length | 10.4 mi |
| Littoral Zone | 53% |
| Public Access | No |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Triangle 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.
Source: USGS Nonindigenous Aquatic Species (NAS) Database. Hover a chip to see scientific name, ecological context, status, and first-observed year.
DNR Fisheries Survey Summary
11 surveys on file from MN DNR Fisheries. Most recent: 2020-07-20 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Yellow Perch | 5.65 | 0.15 lb |
| Tullibee (Cisco) | 5.38 | 1.38 lb |
| Walleye | 4.60 | 2.19 lb |
| Rock Bass | 2.76 | 0.18 lb |
| Northern Pike | 2.09 | 2.92 lb |
| White Sucker | 1.81 | 3.11 lb |
CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.
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
Ice Season
Historical ice data from Minnesota DNR (3 observations).
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 1999-04-22 (1999) | 1997-04-29 (1997) |
Most recent ice-out: 1999-04-22
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
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
What is the water quality grade for Triangle Lake?
- Triangle Lake in Lake County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. 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?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Triangle Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Algae concentration (chlorophyll-a) is 2.1 µg/L. Always check local health department advisories before swimming.
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.
When does Triangle Lake thaw?
- Triangle Lake typically has ice-out around Apr 25.
Explore Triangle Lake across LakeGrade
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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)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated 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