What is the water quality grade for Mill Creek Lake?

Mill Creek Lake in O'Brien County, Wisconsin received a water quality grade of F (Very Poor). Water clarity: 3 ft visibility. Chlorophyll-a (algae): 36.1 µg/L. Surface area: 40 acres.

Is Mill Creek Lake safe to swim in?

Avoid swimming, very poor water quality, potential algae toxins. Mill Creek Lake has an overall water quality grade of F. Algae concentration (chlorophyll-a) is 36.1 µg/L. Always check local health department advisories before swimming.

Mill Creek Lake

O'Brien County, WisconsinEutrophic

Mill Creek Lake is a 40-acre productive, nutrient-rich eutrophic lake in O'Brien County, IA. Water quality is graded F based on 2 sampling years through 2024. Compared to the 1 other monitored lakes in O'Brien County, Mill Creek Lake ranks #2 for water quality.

Source: EPA Water Quality Portal sampling records, local state DNR records, last sampled 2024-09-09. 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 3 ft of visibility. Chlorophyll-a: 36.1 µg/L. Trophic State Index: 64.

Metric	Value	Grade
Water Clarity (Secchi Depth)	3 ft	F
Phosphorus	No data
Chlorophyll-a (Algae)	36.1 µg/L	F
Trophic State Index (TSI)	64	Eutrophic

High nutrients, frequent algae, reduced clarity

Lake Details

Characteristic	Value
Surface Area	40 acres

Location

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County Ranking

Ranked #2 of 2 lakes in O'Brien County

Cleaner Lakes Within 30 Miles

Mill Creek Lake holds Grade F. 4 nearby lakes hold higher grades.

See full comparison →

Nearby Lakes in O'Brien County

Little Sioux Park Lake

Woodbury County

Silver Lake Max Depth

Dickinson County

More Wisconsin Lake Rankings

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Top 25 by overall water quality score

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Grade A/B + low algae filter

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Panfish-rich, public access

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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

Eutrophic Lakes in Wisconsin

Big Creek Lake Storm Lake Max Depth Lost Island Lake Nodaway Lake

Reservoir Info (USACE NID)

Mill Creek Lake is a man-made reservoir impounded by the Mill Creek Lake Dam (completed 1934), built primarily for recreation on the COLE CREEK; earth-type dam, 29 ft tall and 622 ft long.

Surface area: 40 ac
Normal storage: 125 ac-ft
Max storage: 500 ac-ft
Drainage area: 5.44 sq mi
Hazard class: Low
Owner: Iowa Department of Natural Resources

Source: USACE National Inventory of Dams, NID ID IA00837 · Operator website

Data Sources

Water quality data from the EPA Water Quality Portal

Grading methodology based on Metropolitan Council standards

Most recent sample: 2024-09-09

Monitoring stations: 1