Union Lake
Rice County, Minnesota397 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Union Lake. Here is what has been measured.
- Hypereutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- 10 ft max depth
- Public access
- Limited data
Union Lake in Rice County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 3 ft visibility. Phosphorus: 375 µg/L. Chlorophyll-a (algae): 29.2 µg/L. Maximum depth: 10 ft. Surface area: 396.74 acres.
Minnesota DNR's Standard Survey on July 20, 2015 caught 1.60 walleye per gill net at Union Lake. DNR survey details →
Union Lake is a 397-acre highly nutrient-loaded hypereutrophic lake in Rice County, Minnesota with a maximum depth of 10 feet. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 13 other monitored lakes in Rice County, Union Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-10-10. Methodology: how these readings are compared.
What Union Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
- Ice seasonIce-out around Mar 23
Swimming conditions
Readings onlyRecreation use not supported
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. Union Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether 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 Union Lake
These are the measurements Minnesota PCA publishes for Union Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 3 ft of visibility. Phosphorus 375 µg/L. Chlorophyll-a 29.2 µg/L. TSI 72.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 3ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 375µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | 29.2µg/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. | 72 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about Union Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Union Lake typically sits around 59°F at the surface in October. Summer average is about 77°F. Usually warmest in Jul (about 81°F) and coldest in May (about 49°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (49°F) to its warmest (81°F).
Typical surface water temperature by month, from 49 field readings (2011–2025) via the EPA Water Quality Portal. See the full Union Lake water temperature breakdown →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Union Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was very high (1,976,970 cells/mL) on July 18, 2026.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Minnesota DNR's Standard Survey on July 20, 2015 caught 1.60 walleye per gill net at Union Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Union Lake’s water-quality measurements separately, and the water-quality trend over 3 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
3 surveys on file from MN DNR Fisheries. Most recent: 2015-07-20 (Standard Survey).
3 surveys on file · most recent 2015-07-20 (Standard Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Black Bullhead | 98.02 | 4–10 in 2015-07-20 | 0.21 lb |
| Common Carp | 56.44 | 2–27 in 2015-07-20 | 0.48 lb |
| Black Crappie | 20.20 | 6–12 in 1995-08-07 | 0.19 lb |
| Yellow Perch | 12.59 | 5–9 in 2015-07-20 | 0.16 lb |
| White Sucker | 10.89 | 5–17 in 2015-07-20 | 1.22 lb |
| Northern Pike | 10.58 | 13–26 in 2015-07-20 | 2.4 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 Bullhead
Common Carp
Black Crappie
Yellow Perch
From the 2015-07-20 survey
Union Lake is a 403 acre lake located in Rice County near the town of Little Chicago. A county-owned earthen access is located on the northeast side of the lake off Rice County Highway 46. Union Lake has a maximum depth of 10 feet and is placed in Lake Class 43, which includes other Waterville Area Lakes such as…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Union Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — UnionFisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — UnionFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — UnionPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
10 ft
Surface area
397 acres
Shoreline
5.2 mi
Littoral zone
100%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
5 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,004 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Union LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Union Lake
Compare lakeside cabins, hotels, and vacation rentals near Union Lake in Rice 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 Union Lake are listed below.
Top-rated places to stay near Union 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 →
Follow Union Lake’s readings
Email me when new measurements post for this lake. Updates stay free.
Or email
Fishing Union Lake
Water quality readings over time
3 seasons of samples on record (2022–2025). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Worsening3 years
Ice season
Typical ice-out
Mar 23
Earliest Feb 29, 2024 · Latest Apr 29, 2018
Most recent ice-out
Mar 22
2025
12 observations · Minnesota PCA ice records
EPA Impairment Status
Union Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN66-0032-00 · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Union Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Mndot - Heath Creek Rest AreaFaribault · 1.3 mi away · NPDES MN0069639Recent violation
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
Nearby Lakes in Rice County
Frequently asked questions about Union Lake
Where is Union Lake?
- Union Lake is a lake in Rice County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Union Lake?
- Union Lake in Rice County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 3 ft visibility. Phosphorus: 375 µg/L. Chlorophyll-a (algae): 29.2 µg/L. Maximum depth: 10 ft. Surface area: 396.74 acres.
Is Union Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Union Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Union Lake?
- Union Lake typically sits around 59°F at the surface in October, from 49 EPA Water Quality Portal field readings (2011–2025). That is a typical value for the month, not a live reading.
How deep is Union Lake?
- Union Lake has a maximum depth of 10 feet. The lake covers 396.74 acres.
What did the DNR fisheries survey find at Union Lake?
- Minnesota DNR's Standard Survey on July 20, 2015 caught 1.60 walleye per gill net at Union Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Union Lake’s water-quality measurements separately, and the water-quality trend over 3 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
When does Union Lake thaw?
- Union Lake typically has ice-out around Mar 23.
Does Union Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Union Lake (clouds, ice, or an off-season gap). The most recent reading was very high (1,976,970 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Are there boat ramps on Union Lake?
- Union Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Union Lake. Public access is listed as yes.
Can I fish at Union Lake?
- Union Lake has 1 documented boat landing 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 Union Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
Fish species and the cleanest lakes across Minnesota
Fish species and best lakes in Rice County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its readings
Minnesota's cleanest lakes, ranked on agency measurements
More lakes in Minnesota
State Parks Near Union Lake
Other Lakes in Minnesota
Hypereutrophic Lakes in Minnesota
Compare Union Lake With Nearby Lakes
Where this data comes from
35 measurements from 1 monitoring station, 2022–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA35 samples · 2022–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by 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
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
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