Blue Lake
Isanti County, Minnesota296 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Blue Lake. Here is what has been measured.
- Eutrophic
- 31 ft max depth
- Public access
Blue Lake in Isanti County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 8.9 ft visibility. Phosphorus: 44 µg/L. Chlorophyll-a (algae): 21.4 µg/L. Maximum depth: 31 ft. Surface area: 295.99 acres.
Minnesota DNR's Targeted Survey on May 12, 2025 caught 1712.43 black crappie per hour of electrofishing at Blue Lake. Length samples in the latest survey that recorded them ran 3–11 inches. DNR survey details →
Blue Lake is a 296-acre productive, nutrient-rich eutrophic lake in Isanti County, Minnesota with a maximum depth of 31 feet. Overall water quality is improving over recent sampling years. The lake supports 13 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 2 public boat landings. Compared to the 16 other monitored lakes in Isanti County, Blue Lake ranks #11 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-10-08. Methodology: how these readings are compared.
Blue Lake covers about 300 acres in Isanti County. It has 2 public boat landings, so a lakefront rental is not the only way to get a boat on the water. If you are planning to stay, you can search lake houses and cabins around Blue Lake on Vrbo, or look for a hotel room near the lake on Booking.com or Expedia.
What Blue Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch2 documented ramps
- Fishing13 species recorded
- Deep water31 ft surveyed max depth
Swimming conditions
Readings onlyAlgae risk
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. Check local advisories before you swim.
Whether Blue 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 Blue Lake
These are the measurements Minnesota PCA publishes for Blue Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Moderate clarity, visible to about 8.9 ft. Phosphorus 44 µg/L. Chlorophyll-a 21.4 µg/L. TSI 55.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 8.9ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 44µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 21.4µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 55 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Blue Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Blue Lake typically sits around 57°F at the surface in October. Summer average is about 76°F. Usually warmest in Jul (about 79°F) and coldest in Oct (about 57°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (57°F) to its warmest (79°F).
Typical surface water temperature by month, from 154 field readings (2016–2025) via the EPA Water Quality Portal. See the full Blue Lake water temperature breakdown →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Blue Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was very high (1,047,129 cells/mL) on September 28, 2024.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Minnesota DNR's Targeted Survey on May 12, 2025 caught 1712.43 black crappie per hour of electrofishing at Blue Lake. Length samples in the latest survey that recorded them ran 3–11 inches.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Blue Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
11 surveys on file from MN DNR Fisheries. Most recent: 2025-05-12 (Targeted Survey).
11 surveys on file · most recent 2025-05-12 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Black Crappie | 85.95 | 3–11 in 2025-05-12 | 0.19 lb |
| Largemouth Bass | 22.58 | 6–19 in 2021-08-02 | 0.84 lb |
| Bluegill | 20.44 | 2–9 in 2024-05-14 | 0.14 lb |
| Bluntnose Minnow | 19.27 | ||
| Yellow Perch | 10.59 | 5–8 in 2021-08-02 | 0.11 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.
Black Crappie
Largemouth Bass
Bluegill
Yellow Perch
From the 2025-05-12 survey
Blue Lake is a 263-acre lake in southwest Isanti County located five miles northeast of Zimmerman and is within the Rum River watershed. It has a maximum depth of 31 feet and 51 percent of the lake is less than 15 feet deep (134 acres). Water clarity in May and June can be 6 to 9 feet; however, it becomes low in…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Blue Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — BlueFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Blue (1850)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — BlueFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — BluePublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
31 ft
Surface area
296 acres
Shoreline
6.4 mi
Littoral zone
45%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
14 sq mi
HydroLAKES / HydroSHEDS
Elevation
945 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Blue Lake (North)Public
- Blue Lake (East)Public
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Blue Lake
Compare lakeside cabins, hotels, and vacation rentals near Blue Lake in Isanti 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. The water-quality readings cover nutrients and algae, not lodging. Cabins and rentals around Blue Lake are listed below.
Top-rated places to stay near Blue Lake
Prices for Oct 9–11, 4 adults. Change dates on the map below.
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 →
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Fish Species
Click a species to see every lake where it is documented.
Fishing Blue Lake
Water Quality Trend: Improving
Based on 6 years of monitoring (2020–2025).
Water clarity
Worsening6 years
Phosphorus
Improving-12.75 µg/L/yr4 years
Chlorophyll-a
Improving-6.87 µg/L/yr4 years
Nearby Lakes in Isanti County
Frequently asked questions about Blue Lake
Where is Blue Lake?
- Blue Lake is a lake in Isanti County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Blue Lake?
- Blue Lake in Isanti County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 8.9 ft visibility. Phosphorus: 44 µg/L. Chlorophyll-a (algae): 21.4 µg/L. Maximum depth: 31 ft. Surface area: 295.99 acres.
Is Blue Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Blue Lake?
- Blue Lake typically sits around 57°F at the surface in October, from 154 EPA Water Quality Portal field readings (2016–2025). That is a typical value for the month, not a live reading.
How deep is Blue Lake?
- Blue Lake has a maximum depth of 31 feet. The lake covers 295.99 acres.
What fish are in Blue Lake?
- Fish species found in Blue Lake include black bullhead, black crappie, bluegill, bowfin (dogfish), green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, walleye, white sucker, yellow bullhead, yellow perch. Blue Lake is located in Isanti County, Minnesota.
What did the DNR fisheries survey find at Blue Lake?
- Minnesota DNR's Targeted Survey on May 12, 2025 caught 1712.43 black crappie per hour of electrofishing at Blue Lake. Length samples in the latest survey that recorded them ran 3–11 inches. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Blue Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.
Does Blue Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Blue Lake (clouds, ice, or an off-season gap). The most recent reading was very high (1,047,129 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Are there boat ramps on Blue Lake?
- Blue Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Blue Lake (North), Blue Lake (East). Public access is listed as yes.
Can I fish at Blue Lake?
- Blue Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. 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 Blue Lake across LakeQuality
Fish species and the cleanest lakes across Minnesota
Fish species and best lakes in Isanti County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its readings
Lakes in the Rum River Watershed, ranked by water quality
Minnesota's cleanest lakes, ranked on agency measurements
More lakes in Minnesota
Other Lakes in Minnesota
Eutrophic Lakes in Minnesota
Where this data comes from
276 measurements from 2 monitoring stations, 2022–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA276 samples · 2022–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by 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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory