waterbycounty
Compiled federal source snapshot

Iowa Water Quality

Drinking water data for all 98 counties.

Avg SDWIS Compliance Index

73.3

Most Common Five-Year SDWIS Compliance Band

A

Counties with Data

98

of 98 total

County water atlas

Iowa 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

98

Avg SDWIS index

73.3

Watersheds

0

ATTAINS counties

Monitoring

98

63 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 Iowa

Beyond Drinking Water

EPA SDWIS

98/ 98

counties with drinking-water compliance data

125 health violations statewide (5yr)

EPA ATTAINS

—

No §303(d) assessments yet for Iowa

EPA WQP

853

monitoring sites across 98 counties

399,230 total readings (5yr window)

USGS NWIS

63

counties with a fresh pipeline snapshot

13 above38 below

State atlas notes

What stands out in Iowa

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

Adair County has the highest value in the published state SDWIS Compliance Index table at 86.2/100, while Poweshiek County has the lowest at 13.6/100. That is a 72.6 point gap inside one state.

Zero health violations

69

3+ health violations

14

Monitoring hubs

Polk County147 sitesSac County45 sitesHardin County30 sites

Lowest flow reads

Lyon County4%Kossuth County9%Sac County10%

Highest fresh streamflow pipeline snapshots: Decatur County (1172%, observation 2026), Wayne County (325%, observation 2026), Lucas County (253%, observation 2026). These are source-data observations, not household tap-water conclusions.

All Iowa Counties

CountySDWIS Compliance Index
Adair County86.2
Adams County86.2
Allamakee County86.2
Appanoose County86.2
Audubon County86.2
Black Hawk County86.2
Bremer County86.2
Buchanan County86.2
Buena Vista County86.2
Cerro Gordo County86.2
Cherokee County86.2
Clay County86.2
Clayton County86.2
Clinton County86.2
Crawford County86.2
Davis County86.2
Delaware County86.2
Dubuque County86.2
Emmet County86.2
Fayette County86.2
Floyd County86.2
Franklin County86.2
Fremont County86.2
Greene County86.2
Hamilton County86.2
Hardin County86.2
Harrison County86.2
Henry County86.2
Howard County86.2
Humboldt County86.2
Ida County86.2
Jackson County86.2
Jasper County86.2
Jefferson County86.2
Keokuk County86.2
Kossuth County86.2
Lee County86.2
Louisa County86.2
Lucas County86.2
Lyon County86.2
Madison County86.2
Mahaska County86.2
Marion County86.2
Marshall County86.2
Mitchell County86.2
Monona County86.2
Monroe County86.2
Montgomery County86.2
Muscatine County86.2
O'Brien County86.2
Osceola County86.2
Page County86.2
Plymouth County86.2
Pottawattamie County86.2
Ringgold County86.2
Shelby County86.2
Sioux County86.2
Tama County86.2
Taylor County86.2
Union County86.2
Van Buren County86.2
Wapello County86.2
Warren County86.2
Washington County86.2
Wayne County86.2
Winnebago County86.2
Winneshiek County86.2
Worth County86.2
Wright County86.2
Polk County71.5
Scott County70.7
Story County69.8
Linn County69.3
Woodbury County69.0
Des Moines County63.1
Benton County57.3
Dallas County56.9
Jones County52.0
Cedar County51.6
Boone County47.2
Webster County46.1
Hancock County44.5
Dickinson County44.2
Chickasaw County44.0
Guthrie County44.0
Johnson County40.9
Pocahontas County39.3
Clarke County38.9
Cass County32.4
Butler County29.7
Carroll County28.7
Palo Alto County24.5
Sac County17.7
Iowa County17.4
Decatur County17.3
Calhoun County17.0
Mills County16.1
Poweshiek County13.6

Frequently Asked Questions

Which Iowa county has the highest SDWIS Compliance Index?
Adair County has the highest SDWIS Compliance Index in the published Iowa 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.
Which USGS streamflow records are shown across Iowa?
WaterByCounty has 63 fresh USGS pipeline snapshots in the published Iowa 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 Iowa 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 Iowa?
The published county records contain 399,230 results from 853 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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