Barnum Lake
Barnum Lake in Cass County, Minnesota has a water quality grade of A (Excellent). Water clarity: 16.1 ft visibility. Phosphorus: 9 µg/L. Chlorophyll-a (algae): 3 µg/L. Maximum depth: 30 ft. Surface area: 151.34 acres.
- Clarity
- 16.1 ft
- Typical in August
- 73°F
- Max depth
- 30 ft
- Area
- 151 acres
- Type
- Oligotrophic
- Trend
- → Stable
- Public access
- Yes
- Ice-out
- Apr 17
- Open water
- 221 days
Next lake in Cass County
Barnum Lake is a 151-acre cold, clear oligotrophic lake in Cass County, Minnesota with a maximum depth of 30 feet. Water quality is graded A based on 2 sampling years through 2025. The lake supports 8 documented fish species including black crappie, bluegill, and largemouth bass. Public access is available with 1 public boat landing. Compared to the 103 other monitored lakes in Cass County, Barnum Lake ranks #56 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-29. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLow algae
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)
Crystal clear, you can see 16.1 ft down. Phosphorus level: 9 µg/L. Chlorophyll-a: 3 µg/L. Trophic State Index: 38.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 16.1 ft | Not graded |
| Phosphorus | 9 µg/L | Good |
| Chlorophyll-a (Algae) | 3 µg/L | Good |
| Trophic State Index (TSI) | 38 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Barnum Lake
Compare lakeside cabins, hotels, and vacation rentals near Barnum 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.
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Water Temperature
Barnum Lake typically sits around 73°F at the surface in August. Summer average is about 74°F. Usually warmest in Jul (about 78°F) and coldest in Sep (about 66°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 30 field readings (2011–2021) via the EPA Water Quality Portal. See the full Barnum Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 30 ft |
| Surface Area | 151 acres |
| Shoreline Length | 4.5 mi |
| Littoral Zone | 56% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Moccasin LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Barnum Lake
DNR Fisheries Survey Summary
2 surveys on file from MN DNR Fisheries. Most recent: 2001-06-11 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Bluegill | 42.58 | 0.23 lb |
| Largemouth Bass | 12.02 | 0.95 lb |
| Pumpkinseed | 6.92 | 0.19 lb |
| Smallmouth Bass | 5.42 | 0.76 lb |
| Yellow Perch | 4.78 | 0.22 lb |
| Black Crappie | 3.76 | 0.35 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
Largemouth Bass
Pumpkinseed
Smallmouth Bass
From the 2001-06-11 survey
Barnum Lake has an area of 134 acres and a maximum depth of 30 feet. About two-thirds of Barnum Lake is 15 feet or less in depth. Barnum Lake is located about nine miles east and three miles north of Hackensack, MN. The Minnesota Department of Natural Resources (MN DNR) has classified Minnesota's lakes into 43…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Barnum Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — BarnumFisheries Lake Survey · MN DNR LakeFinder
Water Quality Trend: → Stable
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.025 m/yr | 6 |
| Phosphorus | → Stable | +0.09 µg/L/yr | 6 |
| Chlorophyll-a | → Stable | +0.01 µg/L/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (56 observations).
Estimated open water season: 221 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2012-03-24 (2012) | 2013-05-08 (2013) |
| Ice-In | 2004-11-03 (2004) | 2001-12-19 (2001) |
Most recent ice-out: 2025-04-18
County Ranking
Ranked #56 of 104 lakes in Cass County
Nearby Lakes in Cass County
Frequently asked questions about Barnum Lake
What is the water quality grade for Barnum Lake?
- Barnum Lake in Cass County, Minnesota has a water quality grade of A (Excellent). Water clarity: 16.1 ft visibility. Phosphorus: 9 µg/L. Chlorophyll-a (algae): 3 µg/L. Maximum depth: 30 ft. Surface area: 151.34 acres.
Is Barnum Lake safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. Barnum Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 3 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Barnum Lake?
- Barnum Lake typically sits around 73°F at the surface in August, from 30 EPA Water Quality Portal field readings (2011–2021). That is a typical value for the month, not a live reading.
How deep is Barnum Lake?
- Barnum Lake has a maximum depth of 30 feet. The lake covers 151.34 acres.
What fish are in Barnum Lake?
- Fish species found in Barnum Lake include black crappie, bluegill, largemouth bass, northern pike, pumpkinseed, rock bass, smallmouth bass, yellow perch. Barnum Lake is located in Cass County, Minnesota.
When does Barnum Lake thaw?
- Barnum Lake typically has ice-out around Apr 17. Ice typically forms around Nov 24. The open water season is approximately 221 days.
Are there boat ramps on Barnum Lake?
- Barnum Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Moccasin Lake. Public access is listed as yes.
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Where this data comes from
92 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
MNPCA92 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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory
Ice data from Minnesota DNR Climate