Twenty-One Lake
Hubbard County, Minnesota36 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Twenty-One Lake. Here is what has been measured.
- Oligotrophic
- 52 ft max depth
- Public access
- Limited data
Twenty-One Lake in Hubbard County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 17 ft visibility. Phosphorus: 10.5 µg/L. Chlorophyll-a (algae): 3.6 µg/L. Maximum depth: 51.5 ft. Surface area: 35.8 acres.
Minnesota DNR's Standard Survey on July 27, 2015 caught 12.00 northern pike per gill net at Twenty-One Lake. Length samples in the latest survey that recorded them ran 17–29 inches. DNR survey details →
Twenty-One Lake is a 36-acre cold, clear oligotrophic lake in Hubbard County, Minnesota with a maximum depth of 52 feet. The lake supports 6 documented fish species including bluegill, largemouth bass, and northern pike. Public access is available. Compared to the 67 other monitored lakes in Hubbard County, Twenty-One Lake ranks #49 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2023-09-19. Methodology: how these readings are compared.
What Twenty-One Lake is good for
From access and monitoring records, not editorial picks.
- Clear water17 ft of visibility
- Fishing6 species recorded
- Deep water51.5 ft surveyed max depth
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. Check local advisories before you swim.
Whether Twenty-One 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 Twenty-One Lake
These are the measurements Minnesota PCA publishes for Twenty-One Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Crystal clear, you can see 17 ft down. Phosphorus 10.5 µg/L. Chlorophyll-a 3.6 µg/L. TSI 39.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 17ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 10.5µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 3.6µg/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. | 39 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Twenty-One Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Twenty-One Lake typically sits around 60°F at the surface in September. Summer average is about 62°F. Usually warmest in Jul (about 66°F) and coldest in May (about 54°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (54°F) to its warmest (66°F).
Typical surface water temperature by month, from 53 field readings (2023–2023) via the EPA Water Quality Portal. See the full Twenty-One Lake water temperature breakdown →
Minnesota DNR's Standard Survey on July 27, 2015 caught 12.00 northern pike per gill net at Twenty-One Lake. Length samples in the latest survey that recorded them ran 17–29 inches.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Twenty-One Lake’s water-quality measurements separately. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
4 surveys on file from MN DNR Fisheries. Most recent: 2015-07-27 (Standard Survey).
4 surveys on file · most recent 2015-07-27 (Standard Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluegill | 47.41 | 2–7 in 2015-07-27 | 0.06 lb |
| Yellow Perch | 8.24 | 4–8 in 2015-07-27 | 0.21 lb |
| Northern Pike | 7.43 | 17–29 in 2015-07-27 | 1.97 lb |
| Pumpkinseed | 3.54 | 2–6 in 2015-07-27 | 0.11 lb |
| Largemouth Bass | 1.19 | 4–16 in 2015-07-27 | 0.73 lb |
| Rock Bass | 0.50 | 10 in 2015-07-27 | 1.07 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
Yellow Perch
Northern Pike
Pumpkinseed
From the 2015-07-27 survey
Lake Twenty-One is a small, 28 acre lake located within the Paul Bunyan State Forest in Hubbard County. There is a public access and day-use area with picnic sites on the north shore of the lake. There are DNR maintained primitive campground sites on the east shore and south shore between Lake Twenty-One and Nelson…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Twenty-One Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — Twenty-OneFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Twenty-One (1315)Aquatic Plant Report · MN DNR LakeFinder
- —Public Water Access Sites — Twenty-OnePublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
51.5 ft
Surface area
36 acres
Shoreline
1.2 mi
Littoral zone
64%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
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Fish Species
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Fishing Twenty-One Lake
Nearby Lakes in Hubbard County
Frequently asked questions about Twenty-One Lake
Where is Twenty-One Lake?
- Twenty-One Lake is a lake in Hubbard County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Twenty-One Lake?
- Twenty-One Lake in Hubbard County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 17 ft visibility. Phosphorus: 10.5 µg/L. Chlorophyll-a (algae): 3.6 µg/L. Maximum depth: 51.5 ft. Surface area: 35.8 acres.
Is Twenty-One 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 Twenty-One Lake?
- Twenty-One Lake typically sits around 60°F at the surface in September, from 53 EPA Water Quality Portal field readings (2023–2023). That is a typical value for the month, not a live reading.
How deep is Twenty-One Lake?
- Twenty-One Lake has a maximum depth of 51.5 feet. The lake covers 35.8 acres.
What fish are in Twenty-One Lake?
- Fish species found in Twenty-One Lake include bluegill, largemouth bass, northern pike, pumpkinseed, rock bass, yellow perch. Twenty-One Lake is located in Hubbard County, Minnesota.
What did the DNR fisheries survey find at Twenty-One Lake?
- Minnesota DNR's Standard Survey on July 27, 2015 caught 12.00 northern pike per gill net at Twenty-One Lake. Length samples in the latest survey that recorded them ran 17–29 inches. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Twenty-One Lake’s water-quality measurements separately. Catch rate is not a swim clearance and is not a weekly bite report.
Can I fish at Twenty-One Lake?
- Public access to Twenty-One 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.
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Where this data comes from
62 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
MNPCA62 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)
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 details from Minnesota DNR LakeFinder