What is the water quality grade for Union Lake?

Union Lake in Branch County, Wisconsin received a water quality grade of D (Poor). Water clarity: 3.5 ft visibility.

Is Union Lake safe to swim in?

Swimming not recommended, poor water quality with high algae risk. Union Lake has an overall water quality grade of D. Always check local health department advisories before swimming.

What fish are in Union Lake?

Fish species found in Union Lake include Barred fantail darter, Blackchin shiner, Bluegill, Bluntnose minnow, Brindled madtom, Brook silverside, Central mudminnow, Common shiner, Green sunfish, Iowa darter, Johnny darter, Lake herring, Longnose gar, Mimic shiner, Mottled sculpin, Rainbow darter, Rock bass, Sand shiner, Smallmouth bass, Spottail shiner, Western banded killifish, Yellow perch. Union Lake is located in Branch County, Wisconsin.

Union Lake

Branch County, WisconsinLimited DataEutrophic

Union Lake is a productive, nutrient-rich eutrophic lake in Branch County, MI. Water quality is graded D based on 1 sampling years through 2022. The lake supports 22 documented fish species including Barred fantail darter, Blackchin shiner, and Bluegill. Compared to the 4 other monitored lakes in Branch County, Union Lake ranks #4 for water quality.

Source: EPA Water Quality Portal sampling records, local state DNR records, last sampled 2022-09-20. Grade methodology: LakeGrade methodology.

Swimming Safety

Swimming not recommended, poor water quality with high algae risk

Water Quality Grade: D, Poor

Murky, only visible to about 3.5 ft. Trophic State Index: 59.

Metric	Value	Grade
Water Clarity (Secchi Depth)	3.5 ft	D
Phosphorus	No data
Chlorophyll-a (Algae)	No data
Trophic State Index (TSI)	59	Eutrophic

High nutrients, frequent algae, reduced clarity

Fish Species

Click a species to see all Wisconsin and Minnesota lakes where it is found.

→ Best fishing times for Union Lake (14-day solunar calendar)

→ Is it safe to eat fish from Union Lake? (mercury & PFAS guide)

→ Union Lake fishing regulations (limits, seasons, special rules)

Location

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County Ranking

Ranked #4 of 5 lakes in Branch County

Cleaner Lakes Within 30 Miles

Union Lake holds Grade D. One nearby lake has a higher grade.

A
Rose Lake North Basin; Ovid Township
Branch County · 15.5 mi · Two grade letters higher (D → A)

See full comparison →

Nearby Lakes in Branch County

Rose Lake North Basin; Ovid Township

Union Lake Southwest Basin; Sherwood Township Section 11

Branch County

More Wisconsin Lake Rankings

Cleanest lakes in Wisconsin

Top 25 by overall water quality score

Best swimming lakes in Wisconsin

Grade A/B + low algae filter

Family fishing lakes in Wisconsin

Panfish-rich, public access

All Wisconsin lakes

Full state directory

Other Grade D Lakes in Wisconsin

Kimball Lake

Newaygo County · Clarity: 4.5 ft

Community College Pond

Chippewa County · Clarity: 1.5 ft

Little Beaver Lake

Alger County · Clarity: 6.2 ft

Van Etten Lake

Iosco County · Clarity: 5.5 ft

South Pond

Chippewa County · Clarity: 1.3 ft

Eagle Lake

Cass County · Clarity: 6 ft

Eutrophic Lakes in Wisconsin

Kimball Lake Van Etten Lake North Central Basin; Oscoda Township Community College Pond Pentwater Lake Northwest Basin; Pentwater Township

EPA Impairment Status

Union Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).

Causes of impairment

Nutrients (phosphorus, nitrogen)PCBs

A Total Maximum Daily Load (TMDL) plan has been approved.

Source: EPA ATTAINS assessment unit MI040500010403-03 · Official waterbody report

Data Sources

Water quality data from the EPA Water Quality Portal

Impairment status from EPA ATTAINS 303(d) database

Grading methodology based on Metropolitan Council standards

Most recent sample: 2022-09-20

Monitoring stations: 1