Birch Lake is a lake in Unknown County, Minnesota. LakeQuality has not rated this lake (UNRATED) — there is not enough recent sampling to assign a letter.

How deep is Birch Lake?

Birch Lake has a maximum depth of 34 feet. The lake covers 836.35 acres.

Birch Lake

Not yet rated

15 ft clear · Oligotrophic · 836 acres

Limited DataOligotrophic

Birch Lake in Unknown County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 15 ft visibility. Maximum depth: 34 ft. Surface area: 836.35 acres.

Minnesota DNR surveys at Birch Lake average 7.49 walleye per unit of sampling effort (CPUE) across 9 surveys. The most recent is a Standard Survey dated September 5, 2017. Length samples in the latest survey that recorded them ran 8–26 inches. DNR survey details →

Clarity: 15 ft
Max depth: 34 ft
Area: 836 acres
Trend: → Stable
Public access: No

Where to stay →Safe to swim?

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Why Birch Lake has no grade

We grade a lake only when the monitoring record supports a letter: 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 Birch Lake, no EPA ecoregion for this lake, so the National Lakes Assessment condition thresholds cannot be applied. Sampling here has recorded water clarity, but not 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.

Birch Lake is a 836-acre lake in Unknown County, Minnesota with a maximum depth of 34 feet. The lake supports 10 documented fish species including bluegill, cisco species, and largemouth bass. No public access — the lake is private or restricted.

Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-07-12. Grade methodology: LakeQuality methodology.

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Swimming Safety

Not rated

Limited data

Not rated for swimming — there is not enough monitoring data to judge this lake

Compare the safest swimming lakes near Ely →

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Water quality measurements for Birch Lake

These readings exist but are not enough for an A–F grade — see why.

Crystal clear, you can see 15 ft down. Trophic State Index: 38.

Metric	Value	Grade
Water Clarity (Secchi Depth)	15 ft	Not graded
Phosphorus	No recent samples
Chlorophyll-a (Algae)	No recent samples
Trophic State Index (TSI)	38	Oligotrophic

Low nutrients, clear water, excellent for swimming

Where to stay near Birch Lake

Compare lakeside cabins, hotels, and vacation rentals near Birch Lake in Unknown 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 Birch Lake

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DNR fisheries survey

A DNR fisheries survey reports fish abundance and catch rates, not a water-quality grade. LakeQuality does not assign an A–F grade on Birch Lake — official chemistry is on file, not a letter, and the water-quality trend over 6 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.

DNR Fisheries Survey Summary

9 surveys on file from MN DNR Fisheries. Most recent: 2017-09-05 (Standard Survey).

Top Species by Catch Rate

Species	Avg catch rate (CPUE)	Avg Weight
Walleye	7.49	1.61 lb
Tullibee (Cisco)	6.15	0.64 lb
White Sucker	4.19	2.8 lb
Bluegill	2.35	0.19 lb
Northern Pike	2.28	3.61 lb

CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE means more abundant in standardized sampling. This 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.

Walleye

99 fish · 8–26 in · 2017-09-05

Tullibee (Cisco)

51 fish · 7–15 in · 2010-09-13

White Sucker

25 fish · 7–22 in · 2017-09-05

Bluegill

43 fish · 3–8 in · 2017-09-05

From the 2017-09-05 survey

Birch Lake is located approximately 18 miles NE of Ely within the BWCAW. The northern half of the lake is part of Ontario's Quetico Provincial Park. Birch Lake is 836 acres with 397 of these acres in Minnesota. Visitors should be familiar with appropriate regulations when traveling these wilderness areas. Birch Lake…

Source: MN DNR LakeFinder Fisheries Lake Survey

DNR Reports & Resources

Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Birch Lake. 1 report on file.

These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).

—
Fisheries Lake Survey — Birch
Fisheries Lake Survey · MN DNR LakeFinder

Lake Details

Characteristic	Value
Maximum Depth	34 ft
Surface Area	836 acres
Shoreline Length	27.8 mi
Littoral Zone	41%
Public Access	No

Fish Species

bluegill cisco species largemouth bass northern pike pumpkinseed rock bass smallmouth bass walleye white sucker yellow perch

Click a species to see every graded lake where it is documented.

Fishing Birch Lake

Water Quality Trend: → Stable

Based on 6 years of monitoring data (2020-2025).

Metric	Trend	Change/Year	Years
Water Clarity	→ Stable	-0.046 m/yr	6

See year-by-year chart →

EPA Impairment Status

Birch Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).

Causes of impairment

Mercury

A Total Maximum Daily Load (TMDL) plan has been approved.

Source: EPA ATTAINS assessment unit MN38-0532-00 · Official waterbody report

Nearby Lakes in Unknown County

NRCarp Lake8.5 ft clearView →NRSeed Lake7 ft clearView →NRSwamp Lake16.2 ft clearView →NRMountain Lake19 ft clearView →

Frequently asked questions about Birch Lake

Where is Birch Lake?: Birch Lake is a lake in Unknown County, Minnesota. LakeQuality has not rated this lake (UNRATED) — there is not enough recent sampling to assign a letter.
What is the water quality grade for Birch Lake?: Birch Lake in Unknown County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 15 ft visibility. Maximum depth: 34 ft. Surface area: 836.35 acres.
Is Birch Lake safe to swim in?: Not rated for swimming — there is not enough monitoring data to judge this lake. Birch Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
How deep is Birch Lake?: Birch Lake has a maximum depth of 34 feet. The lake covers 836.35 acres.
What fish are in Birch Lake?: Fish species found in Birch Lake include bluegill, cisco species, largemouth bass, northern pike, pumpkinseed, rock bass, smallmouth bass, walleye, white sucker, yellow perch. Birch Lake is located in Unknown County, Minnesota.
What did the DNR fisheries survey find at Birch Lake?: Minnesota DNR surveys at Birch Lake average 7.49 walleye per unit of sampling effort (CPUE) across 9 surveys. The most recent is a Standard Survey dated September 5, 2017. Length samples in the latest survey that recorded them ran 8–26 inches. A DNR fisheries survey reports fish abundance and catch rates, not a water-quality grade. LakeQuality does not assign an A–F grade on Birch Lake — official chemistry is on file, not a letter, and the water-quality trend over 6 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.

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Where this data comes from

68 measurements from 18 monitoring stations, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.

Collected and reported by

Minnesota Pollution Control Agency - Ambient Surface WaterMNPCA68 samples · 2020–2025

Analytical methods

Field measurement/observation, generic method

Monitoring station identifiers (18)

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