Isabella Lake
Isabella Lake in Lake County, Minnesota has a water quality grade of A (Excellent). 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.
- Clarity
- 4.4 ft
- Typical in August
- 70°F
- Max depth
- 19 ft
- Area
- 1,257 acres
- Type
- Eutrophic
- Trend
- ↓ Declining
- Public access
- Yes
Next lake in Lake County
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). Water quality is graded A based on 2 sampling years through 2025. 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. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLimited data
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A (Excellent)
Murky, only visible to about 4.4 ft. Phosphorus level: 19 µg/L. Chlorophyll-a: 5.8 µg/L. Trophic State Index: 50.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 4.4 ft | Not graded |
| Phosphorus | 19 µg/L | Good |
| Chlorophyll-a (Algae) | 5.8 µg/L | Good |
| Trophic State Index (TSI) | 50 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Isabella Lake
Compare lakeside cabins, hotels, and vacation rentals near Isabella 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 Isabella Lake
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Water Temperature
Isabella Lake typically sits around 70°F at the surface in August. 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.
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 →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 19 ft |
| Average Depth | 8 ft |
| Surface Area | 1,257 acres |
| Shoreline Length | 17.1 mi |
| Littoral Zone | 77% |
| Public Access | Yes |
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 Isabella Lake
DNR Fisheries Survey Summary
9 surveys on file from MN DNR Fisheries. Most recent: 2016-09-19 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| BNS | 24.50 | — |
| SUN | 12.80 | — |
| Bluegill | 8.00 | — |
| Walleye | 7.86 | 0.63 lb |
| LKW | 4.83 | 0.63 lb |
| White Sucker | 4.29 | 1.52 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.
Bluegill
Walleye
LKW
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
Water Quality Trend: ↓ Declining
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.084 m/yr | 2 |
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
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN38-0396-00 · Official waterbody report
County Ranking
Ranked #9 of 35 lakes in Lake County
Nearby Lakes in Lake County
Frequently asked questions about Isabella Lake
What is the water quality grade for Isabella Lake?
- Isabella Lake in Lake County, Minnesota has a water quality grade of A (Excellent). 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?
- Excellent for swimming, crystal clear water with minimal algae. Isabella Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 5.8 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Isabella Lake?
- Isabella Lake typically sits around 70°F at the surface in August, 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.
Explore Isabella Lake across LakeGrade
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High nutrients, frequent algae, reduced clarity
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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)
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