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Not health advice. Contact your local water utility for concerns.
Data from EPA Water Quality Reports. For official information, contact your water utility or health department.
Compare water quality across 16 counties in Iowa
16 counties ranked by average water quality score
| Rank | County | Avg Score | Grade | Cities | Population | Score Range |
|---|---|---|---|---|---|---|
| 1 | Polk County | 100 | A | 5 | 466,723 | 100 - 100 |
| 2 | Johnson County | 100 | A | 3 | 114,347 | 100 - 100 |
| 3 | Pottawattamie County | 100 | A | 1 | 64,447 | 100 - 100 |
| 4 | Marshall County | 100 | A | 1 | 27,680 | 100 - 100 |
| 5 | Webster County | 100 | A | 1 | 25,874 | 100 - 100 |
| 6 | Linn County | 99 | A | 2 | 183,987 | 97 - 100 |
| 7 | Story County | 99 | A | 1 | 55,177 | 99 - 99 |
| 8 | Cerro Gordo County | 99 | A | 1 | 27,338 | 99 - 99 |
| 9 | Black Hawk County | 97 | A | 2 | 110,217 | 94 - 100 |
| 10 | Wapello County | 96 | A | 1 | 25,529 | 96 - 96 |
| 11 | Des Moines County | 94 | A | 1 | 26,015 | 94 - 94 |
| 12 | Clinton County | 94 | A | 1 | 24,769 | 94 - 94 |
| 13 | Scott County | 88 | B | 1 | 147,720 | 88 - 88 |
| 14 | Dubuque County | 85 | B | 1 | 59,667 | 85 - 85 |
| 15 | Muscatine County | 74 | C | 1 | 25,516 | 74 - 74 |
| 16 | Woodbury County | 72 | C | 1 | 85,791 | 72 - 72 |
5 cities • 466,723 residents
2 cities • 183,987 residents
See all 16 counties in the ranking table above
Our county-level water quality analysis aggregates data from municipal water systems across Iowa. Each county's score represents the average water quality across all analyzed cities within that county, weighted by population served.
With 16 counties and 24 cities analyzed, this data helps residents understand regional water quality patterns in Iowa. County scores range from 72/100 to 100/100, reflecting the diversity of water sources and treatment infrastructure across the state.
All analyzed counties in Iowa maintain average scores above 70, indicating generally acceptable water quality standards statewide. Individual city scores may vary, so residents should still review their specific city's report.