What is the water quality grade for Summit Lake?

Summit Lake in Union County, Wisconsin received a water quality grade of F (Very Poor). Water clarity: 1.4 ft visibility. Chlorophyll-a (algae): 45.7 µg/L. Surface area: 202 acres.

Is Summit Lake safe to swim in?

Avoid swimming, very poor water quality, potential algae toxins. Summit Lake has an overall water quality grade of F. Algae concentration (chlorophyll-a) is 45.7 µg/L. Always check local health department advisories before swimming.

Summit Lake

Union County, WisconsinHypereutrophic

Summit Lake is a 202-acre highly nutrient-loaded hypereutrophic lake in Union County, IA. Water quality is graded F based on 2 sampling years through 2024. Compared to the 5 other monitored lakes in Union County, Summit Lake ranks #5 for water quality.

Source: EPA Water Quality Portal sampling records, local state DNR records, last sampled 2024-09-30. Grade methodology: LakeGrade methodology.

Swimming Safety

Avoid swimming, very poor water quality, potential algae toxins

Water Quality Grade: F, Very Poor

Very murky, less than 1.4 ft of visibility. Chlorophyll-a: 45.7 µg/L. Trophic State Index: 70.

Metric	Value	Grade
Water Clarity (Secchi Depth)	1.4 ft	F
Phosphorus	No data
Chlorophyll-a (Algae)	45.7 µg/L	F
Trophic State Index (TSI)	70	Hypereutrophic

Very high nutrients, dense algae, poor clarity

Lake Details

Characteristic	Value
Surface Area	202 acres

Location

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County Ranking

Ranked #5 of 6 lakes in Union County

Cleaner Lakes Within 30 Miles

Summit Lake holds Grade F. 3 nearby lakes hold higher grades.

See full comparison →

Nearby Lakes in Union 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

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Panfish-rich, public access

All Wisconsin lakes

Full state directory

Other Grade F Lakes in Wisconsin

Big Creek Lake

Polk County · Clarity: 2.6 ft

Arrowhead Lake

Pottawattamie County · Clarity: 1.8 ft

White Oak Lake

Mahaska County · Clarity: 1.4 ft

Crystal Lake Max Depth

Hancock County · Clarity: 1.6 ft

Hannen Lake

Benton County · Clarity: 1.2 ft

Briggs Woods Lake

Hamilton County · Clarity: 1.5 ft

Hypereutrophic Lakes in Wisconsin

White Oak Lake Hannen Lake Briggs Woods Lake Union Grove Lake

Reservoir Info (USACE NID)

Summit Lake is a man-made reservoir impounded by the Summit Lake Dam (completed 1935), built primarily for recreation on the TR-WEST PLATTE RIVER; earth-type dam, 26 ft tall and 1,000 ft long.

Surface area: 202 ac
Normal storage: 1,410 ac-ft
Max storage: 2,680 ac-ft
Drainage area: 15.7 sq mi
Hazard class: Low
Owner: Creston Waterworks

Source: USACE National Inventory of Dams, NID ID IA01379 · Operator website

EPA Impairment Status

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

Causes of impairment

Algal growthPCBsTurbidity

Source: EPA ATTAINS assessment unit IA 05-PLA-1470 · Official waterbody report · Matched by proximity (1.17 km)

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: 2024-09-30

Monitoring stations: 1