Isabella Lake
Lake County, Minnesota1,257 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Isabella Lake. Here is what has been measured.
- Eutrophic
- Impaired · Mercury
- 19 ft max depth
- Public access
- Limited data
Isabella Lake in Lake County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 4.4 ft visibility. Phosphorus: 19 µg/L. Chlorophyll-a (algae): 5.8 µg/L. Maximum depth: 19 ft. Surface area: 1257.23 acres.
Minnesota DNR's Standard Survey on September 19, 2016 caught 7.25 walleye per gill net at Isabella Lake. Length samples in the latest survey that recorded them ran 7–21 inches. DNR survey details →
Free interactive depth-contour map of Isabella Lake, reaching a maximum surveyed depth of 15 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Minnesota DNR.
Isabella Lake is a 1,257-acre productive, nutrient-rich eutrophic lake in Lake County, Minnesota with a maximum depth of 19 feet (8-foot average). Overall water quality is declining over recent sampling years. The lake supports 11 documented fish species including black crappie, bluegill, and lake whitefish. Public access is available. Compared to the 34 other monitored lakes in Lake County, Isabella Lake ranks #9 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-09. Methodology: how these readings are compared.
What Isabella Lake is good for
From access and monitoring records, not editorial picks.
- Fishing11 species recorded
- Big water1,257 acres
Swimming conditions
Readings onlyLimited data
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Isabella Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether Isabella 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 Isabella Lake
These are the measurements Minnesota PCA publishes for Isabella 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 4.4 ft. Phosphorus 19 µg/L. Chlorophyll-a 5.8 µg/L. TSI 50.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 4.4ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 19µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 5.8µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 50 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Isabella Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Isabella Lake typically sits around 44°F at the surface in October. Summer average is about 68°F. Usually warmest in Jul (about 71°F) and coldest in Oct (about 44°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (44°F) to its warmest (71°F).
Typical surface water temperature by month, from 65 field readings (2011–2025) via the EPA Water Quality Portal. See the full Isabella Lake water temperature breakdown →
Minnesota DNR's Standard Survey on September 19, 2016 caught 7.25 walleye per gill net at Isabella Lake. Length samples in the latest survey that recorded them ran 7–21 inches.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Isabella Lake’s water-quality measurements separately, and the water-quality trend over 2 years of monitoring is declining. 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: 2016-09-19 (Standard Survey).
9 surveys on file · most recent 2016-09-19 (Standard Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluegill | 8.00 | 1–4 in 2016-09-19 | |
| Walleye | 7.86 | 7–21 in 2016-09-19 | 0.63 lb |
| White Sucker | 4.29 | 6–21 in 2016-09-19 | 1.52 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.
Bluegill
Walleye
White Sucker
From the 2016-09-19 survey
Isabella Lake has an area of 1,257 acres and has a maximum depth of 19 feet. It is located entirely with the Boundary Waters Canoe Area Wilderness (BWCAW) approximately 13 miles north of Isabella, MN off of USFS Road 377 (Tomahawk Road). The lake has three different access points. The main access to Isabella Lake is a…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Isabella Lake. 2 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — IsabellaFisheries Lake Survey · MN DNR LakeFinder
- —Public Water Access Sites — IsabellaPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
19 ft
Average depth
8 ft
Surface area
1,257 acres
Shoreline
17.1 mi
Littoral zone
77%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
27 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,542 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Stays via Stay22
Stays near Isabella Lake
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Fish Species
Click a species to see every lake where it is documented.
Fishing Isabella Lake
Water quality readings over time
2 seasons of samples on record (2020–2025). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Worsening2 years
EPA Impairment Status
Isabella 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 MN38-0396-00 · Official waterbody report
Nearby Lakes in Lake County
Frequently asked questions about Isabella Lake
Where is Isabella Lake?
- Isabella 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 Isabella Lake?
- Isabella Lake in Lake County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 4.4 ft visibility. Phosphorus: 19 µg/L. Chlorophyll-a (algae): 5.8 µg/L. Maximum depth: 19 ft. Surface area: 1257.23 acres.
Is Isabella Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Isabella Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
What is the water temperature of Isabella Lake?
- Isabella Lake typically sits around 44°F at the surface in October, from 65 EPA Water Quality Portal field readings (2011–2025). That is a typical value for the month, not a live reading.
How deep is Isabella Lake?
- Isabella Lake has a maximum depth of 19 feet and an average depth of 8 feet. The lake covers 1257.23 acres.
What fish are in Isabella Lake?
- Fish species found in Isabella Lake include black crappie, bluegill, lake whitefish, largemouth bass, northern pike, pumpkinseed, rock bass, sunfish, walleye, white sucker, yellow perch. Isabella Lake is located in Lake County, Minnesota.
What did the DNR fisheries survey find at Isabella Lake?
- Minnesota DNR's Standard Survey on September 19, 2016 caught 7.25 walleye per gill net at Isabella Lake. Length samples in the latest survey that recorded them ran 7–21 inches. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Isabella Lake’s water-quality measurements separately, and the water-quality trend over 2 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
Can I fish at Isabella Lake?
- Public access to Isabella Lake is listed as yes on the lake record. 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 Isabella Lake across LakeQuality
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Where this data comes from
26 measurements from 2 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 Water
MNPCA26 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (2)
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