Three Island Lake
Three Island Lake in Cass County, Minnesota has a water quality grade of A (Excellent). Water clarity: 9 ft visibility. Phosphorus: 12 µg/L. Chlorophyll-a (algae): 3.3 µg/L. Maximum depth: 13 ft. Surface area: 287.89 acres.
- Clarity
- 9 ft
- Typical in August
- 75°F
- Max depth
- 13 ft
- Area
- 288 acres
- Type
- Mesotrophic
- Trend
- ↓ Declining
- Public access
- Yes
Next lake in Cass County
Three Island Lake is a 288-acre mesotrophic lake in Cass County, Minnesota with a maximum depth of 13 feet. Water quality is graded A based on 2 sampling years through 2023. Overall water quality is declining over recent sampling years. The lake supports 8 documented fish species including black crappie, bluegill, and hybrid sunfish. Public access is available with 1 public boat landing. Compared to the 103 other monitored lakes in Cass County, Three Island Lake ranks #40 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2023-09-06. Grade methodology: LakeGrade methodology.
Watch Three Island Lake water quality
Subscribe for LakeQuality updates by email. No spam, unsubscribe anytime.
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)
Moderate clarity, visible to about 9 ft. Phosphorus level: 12 µg/L. Chlorophyll-a: 3.3 µg/L. Trophic State Index: 43.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 9 ft | Not graded |
| Phosphorus | 12 µg/L | Good |
| Chlorophyll-a (Algae) | 3.3 µg/L | Good |
| Trophic State Index (TSI) | 43 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Three Island Lake
Compare lakeside cabins, hotels, and vacation rentals near Three Island Lake in Cass 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 Three Island Lake
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Minnesota’s top lakes →
Water Temperature
Three Island Lake typically sits around 75°F at the surface in August. Summer average is about 73°F. Usually warmest in Aug (about 75°F) and coldest in May (about 65°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 24 field readings (2010–2023) via the EPA Water Quality Portal. See the full Three Island Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 13 ft |
| Surface Area | 288 acres |
| Shoreline Length | 7.5 mi |
| Littoral Zone | 100% |
| Public Access | Yes |
Recreation & Access
- Three Island LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Three Island Lake
DNR Fisheries Survey Summary
6 surveys on file from MN DNR Fisheries. Most recent: 2022-07-18 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Bluegill | 15.66 | 0.15 lb |
| Pumpkinseed | 8.59 | 0.22 lb |
| Northern Pike | 6.28 | 1.83 lb |
| Yellow Perch | 5.21 | 0.17 lb |
| Black Crappie | 1.79 | 0.3 lb |
| Walleye | 1.66 | 4.1 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
Pumpkinseed
Northern Pike
Yellow Perch
From the 2022-07-18 survey
Three Island is a 288-acre lake with 7 miles of shoreline and a maximum depth of 13 feet located east of Walker, MN. A US Forest Service owned public access is located on the north shore. The DNR has classified Minnesota's lakes into 43 different classes based on physical, chemical and other characteristics. Three…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Three Island Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — Three IslandFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Three Island (1147)Aquatic Plant Report · MN DNR LakeFinder
- —Public Water Access Sites — Three IslandPublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: ↓ Declining
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Phosphorus | ↓ Declining | +2 µg/L/yr | 2 |
| Chlorophyll-a | ↓ Declining | +1.3 µg/L/yr | 2 |
County Ranking
Ranked #40 of 104 lakes in Cass County
Nearby Lakes in Cass County
Frequently asked questions about Three Island Lake
What is the water quality grade for Three Island Lake?
- Three Island Lake in Cass County, Minnesota has a water quality grade of A (Excellent). Water clarity: 9 ft visibility. Phosphorus: 12 µg/L. Chlorophyll-a (algae): 3.3 µg/L. Maximum depth: 13 ft. Surface area: 287.89 acres.
Is Three Island Lake safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. Three Island Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 3.3 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Three Island Lake?
- Three Island Lake typically sits around 75°F at the surface in August, from 24 EPA Water Quality Portal field readings (2010–2023). That is a typical value for the month, not a live reading.
How deep is Three Island Lake?
- Three Island Lake has a maximum depth of 13 feet. The lake covers 287.89 acres.
What fish are in Three Island Lake?
- Fish species found in Three Island Lake include black crappie, bluegill, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, white sucker, yellow perch. Three Island Lake is located in Cass County, Minnesota.
Are there boat ramps on Three Island Lake?
- Three Island Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Three Island Lake. Public access is listed as yes.
Explore Three Island Lake across LakeGrade
Fish species and top-graded lakes across Minnesota
Fish species and best lakes in Cass County
Species activity outlook by water temperature and season
Top lakes and where to stay in the Brainerd Lakes area
Where to stay at Minnesota's top lakes, each with its grade
Lakes in the Mississippi Headwaters, ranked by water quality
Lakes in the Pine River Watersheds (Brainerd Lakes), ranked by water quality
Moderate nutrients, good water quality
Minnesota's cleanest and most-polluted lakes, ranked
More Minnesota Lake Rankings
Other Grade A Lakes in Minnesota
Mesotrophic Lakes in Minnesota
Where this data comes from
15 measurements from 1 monitoring station, 2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA15 samples · 2023
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory