North Union Lake
Douglas County, Minnesota118 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for North Union Lake. Here is what has been measured.
- Oligotrophic
- zebra mussel
- 42 ft max depth
- Limited data
North Union Lake in Douglas County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 20.3 ft visibility. Phosphorus: 13.5 µg/L. Chlorophyll-a (algae): 2.4 µg/L. Maximum depth: 42 ft. Surface area: 118.41 acres.
Minnesota DNR's Standard Survey on August 8, 2018 caught 1.00 walleye per gill net at North Union Lake. DNR survey details →
North Union Lake is a 118-acre cold, clear oligotrophic lake in Douglas County, Minnesota with a maximum depth of 42 feet (5-foot average). Overall water quality is declining over recent sampling years. The lake supports 13 documented fish species including black crappie, bluegill, and brown bullhead. No public access — the lake is private or restricted. Compared to the 36 other monitored lakes in Douglas County, North Union Lake ranks #24 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-09-15. Methodology: how these readings are compared.
What North Union Lake is good for
From access and monitoring records, not editorial picks.
- Clear water20.3 ft of visibility
- Fishing13 species recorded
- Deep water42 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 North Union 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 North Union Lake
These are the measurements Minnesota PCA publishes for North Union 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 20.3 ft down. Phosphorus 13.5 µg/L. Chlorophyll-a 2.4 µg/L. TSI 38.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 20.3ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 13.5µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 2.4µg/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. | 38 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about North Union Lake
Answers come straight from the public measurements and survey records on this page.
Minnesota DNR's Standard Survey on August 8, 2018 caught 1.00 walleye per gill net at North Union Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows North Union Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
7 surveys on file from MN DNR Fisheries. Most recent: 2018-08-08 (Standard Survey).
7 surveys on file · most recent 2018-08-08 (Standard Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluegill | 21.40 | 4–8 in 2018-08-08 | 0.2 lb |
| Golden Shiner | 15.12 | ||
| Black Bullhead | 8.12 | 11–13 in 2002-08-05 | 1 lb |
| Yellow Bullhead | 7.77 | 8–13 in 2018-08-08 | 0.67 lb |
| Pumpkinseed | 5.98 | 4–8 in 2018-08-08 | 0.29 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
Black Bullhead
Yellow Bullhead
Pumpkinseed
From the 2018-08-08 survey
North Union, Stony, and Lottie (Taylor) lakes form a chain of lakes between Brophy and Cowdry Lakes in Douglas County. North Union Lake is the upper or first lake in this chain of interconnected lakes. Brophy Lake discharges into North Union. North Union outlets to Stony Lake. None of these three small basins have…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for North Union Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — North UnionFisheries Lake Survey · MN DNR LakeFinder
Lake Details
Max depth
42 ft
Average depth
5 ft
Surface area
118 acres
Shoreline
4.1 mi
Littoral zone
75%
Share shallower than 15 ft
Public access
No
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
9 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,355 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Stays via Stay22
Stays near North Union Lake
Compare lakeside cabins, hotels, and vacation rentals near North Union Lake in Douglas 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 North Union Lake
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Follow North Union Lake’s readings
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Fish Species
Click a species to see every lake where it is documented.
Fishing North Union Lake
- → North Union Lake fishing: DNR survey catch rates, species & stocking
- → North Union Lake fishing forecast & best times (species outlook + 14-day solunar calendar)
- → North Union Lake fishing regulations (limits, seasons, special rules)
- → Is it safe to eat fish from North Union Lake? (mercury & PFAS guide)
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
Water Quality Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Water clarity
Stable6 years
Phosphorus
Worsening+0.83 µg/L/yr6 years
Chlorophyll-a
Stable0 µg/L/yr6 years
Nearby Lakes in Douglas County
Frequently asked questions about North Union Lake
Where is North Union Lake?
- North Union Lake is a lake in Douglas County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of North Union Lake?
- North Union Lake in Douglas County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 20.3 ft visibility. Phosphorus: 13.5 µg/L. Chlorophyll-a (algae): 2.4 µg/L. Maximum depth: 42 ft. Surface area: 118.41 acres.
Is North Union Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
How deep is North Union Lake?
- North Union Lake has a maximum depth of 42 feet and an average depth of 5 feet. The lake covers 118.41 acres.
What fish are in North Union Lake?
- Fish species found in North Union Lake include black crappie, bluegill, brown bullhead, common carp, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, rock bass, tullibee (cisco), walleye, yellow bullhead, yellow perch. North Union Lake is located in Douglas County, Minnesota.
What did the DNR fisheries survey find at North Union Lake?
- Minnesota DNR's Standard Survey on August 8, 2018 caught 1.00 walleye per gill net at North Union Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows North Union Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
Can I fish at North Union Lake?
- Public access to North Union Lake is listed as no on the lake record, so confirm before you make the trip. 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
15 measurements from 1 monitoring station, 2021–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA15 samples · 2021–2024
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 size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder