Polly Lake
Polly Lake in Lake County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 4.5 ft visibility. Maximum depth: 21 ft. Surface area: 485.24 acres.
- Clarity
- 4.5 ft
- Max depth
- 21 ft
- Area
- 485 acres
- Trend
- ↓ Declining
- Public access
- No
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Why Polly 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 Polly Lake, the only measurement available is water clarity, which is not a water-quality indicator on its own — EPA's National Lakes Assessment does not grade clarity. 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.
Polly Lake is a 485-acre lake in Lake County, Minnesota with a maximum depth of 21 feet (9-foot average). Overall water quality is declining over recent sampling years. The lake supports 8 documented fish species including green sunfish, northern pike, and pumpkinseed. No public access — the lake is private or restricted.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-08-03. 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 Polly Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Murky, only visible to about 4.5 ft. Trophic State Index: 55.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 4.5 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 55 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Polly Lake
Compare lakeside cabins, hotels, and vacation rentals near Polly 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 Polly Lake
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Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 21 ft |
| Average Depth | 9 ft |
| Surface Area | 485 acres |
| Shoreline Length | 18.6 mi |
| Littoral Zone | 78% |
| 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 Polly Lake
DNR Fisheries Survey Summary
3 surveys on file from MN DNR Fisheries. Most recent: 2016-09-12 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| White Sucker | 10.55 | 1.69 lb |
| Walleye | 7.58 | 0.88 lb |
| Yellow Perch | 3.12 | 0.15 lb |
| Green Sunfish | 1.71 | — |
| BNS | 1.29 | — |
| Pumpkinseed | 0.93 | 0.07 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.
White Sucker
Walleye
Yellow Perch
Pumpkinseed
From the 2016-09-12 survey
Polly Lake has an area of 485 acres with a maximum depth of 21 feet and has brown tinted water with clarity around 7 feet. The lake is located within the BWCAW about 23 miles northeast of Isabella, and is a part of a popular canoe route called the Girl Chain. There are three portage routes into the lake. An 85 rod…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Polly Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — PollyFisheries Lake Survey · MN DNR LakeFinder
Water Quality Trend: ↓ Declining
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.1 m/yr | 3 |
EPA Impairment Status
Polly Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN38-0104-00 · Official waterbody report
Nearby Lakes in Lake County
Frequently asked questions about Polly Lake
What is the water quality grade for Polly Lake?
- Polly Lake in Lake County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 4.5 ft visibility. Maximum depth: 21 ft. Surface area: 485.24 acres.
Is Polly Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Polly 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 Polly Lake?
- Polly Lake has a maximum depth of 21 feet and an average depth of 9 feet. The lake covers 485.24 acres.
What fish are in Polly Lake?
- Fish species found in Polly Lake include green sunfish, northern pike, pumpkinseed, rock bass, smallmouth bass, walleye, white sucker, yellow perch. Polly Lake is located in Lake County, Minnesota.
Explore Polly Lake across LakeGrade
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Where this data comes from
5 measurements from 3 monitoring stations, 2022–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA5 samples · 2022–2024
Analytical methods
- Field measurement/observation, generic method
Monitoring station identifiers (3)
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