waterbycounty
Compiled federal source snapshot

Wisconsin Water Quality

Drinking water data for all 71 counties.

Avg SDWIS Compliance Index

36.4

Most Common Five-Year SDWIS Compliance Band

F

Counties with Data

71

of 71 total

County water atlas

Wisconsin water signals by county

A state-level 2.5D view across drinking-water compliance, watershed impairment, monitoring density, and streamflow snapshot context. Pin any county, switch layers, then use the lens controls to compare index ranges, recorded violation rates, or impaired watersheds without leaving the page.

Counties

71

Avg SDWIS index

36.4

Watersheds

71

ATTAINS counties

Monitoring

71

53 fresh USGS snapshots

State atlas layers combine EPA SDWIS health-based violations, EPA ATTAINS 303(d) impairment assessments, EPA Water Quality Portal monitoring sites, and representative USGS NWIS streamflow gauges. Streamflow values appear only for fresh pipeline snapshots, not as a continuously updated stream. County pages include the observation time and year.

Prepared by ByCounty Editorial TeamPublished by WaterByCounty

Multi-source coverage in Wisconsin

Beyond Drinking Water

EPA SDWIS

71/ 71

counties with drinking-water compliance data

502 health violations statewide (5yr)

EPA ATTAINS

26.8%

avg impaired across 71 counties

1,993 of 10,309 assessed bodies impaired

EPA WQP

7,631

monitoring sites across 71 counties

4,699,760 total readings (5yr window)

USGS NWIS

53

counties with a fresh pipeline snapshot

2 above46 below

State atlas notes

What stands out in Wisconsin

County water quality is not one number. The strongest read comes from comparing drinking-water compliance against watershed impairment, monitoring density, and streamflow context. Use these signals as a starting point, then open any county profile for source-level detail.

Compliance spread

Door County has the highest value in the published state SDWIS Compliance Index table at 86.2/100, while Florence County has the lowest at 5.4/100. That is a 80.8 point gap inside one state.

Zero health violations

1

3+ health violations

55

Watershed pressure

The atlas impairment layer points to counties where assessed water bodies are most likely to miss state quality standards. Assessment density varies, so compare the percentage with the number of assessed bodies on the county page.

Milwaukee County74.3%Pepin County72.7%Calumet County70.3%

Monitoring hubs

Milwaukee County518 sitesDane County375 sitesBrown County346 sites

Lowest flow reads

Manitowoc County11%Douglas County11%Ashland County11%

Highest fresh streamflow pipeline snapshots: Waukesha County (188%, observation 2026), Rock County (120%, observation 2026), Kenosha County (105%, observation 2026). These are source-data observations, not household tap-water conclusions.

All Wisconsin Counties

CountySDWIS Compliance Index
Door County86.2
Milwaukee County72.3
Wood County65.4
Outagamie County65.1
Portage County65.1
Sheboygan County65.1
Brown County64.5
Dane County64.1
Racine County60.7
La Crosse County59.8
Washington County59.1
Winnebago County56.5
Fond du Lac County55.7
Chippewa County54.9
Rock County54.9
St. Croix County54.3
Waupaca County52.5
Eau Claire County52.0
Walworth County49.3
Pierce County47.5
Kewaunee County47.4
Marathon County46.8
Manitowoc County46.4
Kenosha County44.9
Shawano County43.7
Waushara County42.8
Ozaukee County41.6
Sauk County41.4
Calumet County39.7
Dunn County39.5
Polk County39.4
Marinette County37.6
Monroe County37.5
Green County37.2
Green Lake County37.0
Juneau County35.2
Burnett County32.5
Trempealeau County32.2
Lincoln County32.1
Douglas County31.8
Jefferson County31.4
Barron County30.1
Price County28.0
Waukesha County27.6
Washburn County26.1
Buffalo County25.9
Oneida County25.8
Dodge County25.0
Bayfield County24.1
Oconto County23.3
Clark County23.1
Grant County23.1
Lafayette County22.7
Columbia County22.4
Jackson County21.7
Richland County21.2
Vernon County18.0
Langlade County17.9
Iowa County17.3
Crawford County16.6
Sawyer County16.6
Taylor County16.6
Iron County15.1
Adams County11.6
Vilas County11.2
Forest County11.0
Marquette County10.7
Ashland County10.6
Pepin County8.3
Rusk County7.4
Florence County5.4

Frequently Asked Questions

Which Wisconsin county has the highest SDWIS Compliance Index?
Door County has the highest SDWIS Compliance Index in the published Wisconsin cohort at 86.2/100. This WaterByCounty relative comparison is not an EPA score and does not establish current conditions for a utility or address.
What does the Five-Year SDWIS Compliance Band mean?
The band is derived only from each county aggregation's recorded health-violation rate per 100,000 people served for the stated five-year source window. It is separate from the relative SDWIS Compliance Index and is not a current determination for a specific utility or address.
What does EPA ATTAINS report across Wisconsin?
Across 71 published Wisconsin county records with EPA ATTAINS data, 1,993 of 10,309 assessed water bodies are listed as impaired. This is a watershed assessment and does not describe finished household tap water.
Which USGS streamflow records are shown across Wisconsin?
WaterByCounty has 53 fresh USGS pipeline snapshots in the published Wisconsin cohort. Each county page shows its observation timestamp and year. A pipeline snapshot is not a continuously updated reading or a tap-water safety measure.
Where can Wisconsin residents find current official information?
Review the applicable utility's Consumer Confidence Report, active notices, and the state drinking-water agency. WaterByCounty's county-level historical aggregations do not establish the current status of a specific utility, address, private well, or household plumbing system.
What does Water Quality Portal monitoring volume show in Wisconsin?
The published county records contain 4,699,760 results from 7,631 monitoring locations in the site's five-year aggregation. Monitoring volume does not by itself indicate better or worse water quality.

Data Sources

Drinking-water compliance data from the EPA Safe Drinking Water Information System (SDWIS) via the ECHO enforcement database. The WaterByCounty SDWIS Compliance Index reflects the recorded rate and is not an EPA score.

Disclaimer: This data is informational only. It is not health, legal, or professional advice. For concerns about your specific water supply, contact your local water utility.

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