waterbycounty
Compiled federal source snapshot

Maine Water Quality

Drinking water data for all 16 counties.

Avg SDWIS Compliance Index

32.1

Most Common Five-Year SDWIS Compliance Band

F

Counties with Data

16

of 16 total

County water atlas

Maine 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

16

Avg SDWIS index

32.1

Watersheds

9

ATTAINS counties

Monitoring

16

13 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 Maine

Beyond Drinking Water

EPA SDWIS

16/ 16

counties with drinking-water compliance data

187 health violations statewide (5yr)

EPA ATTAINS

69.0%

avg impaired across 9 counties

10 of 23 assessed bodies impaired

EPA WQP

566

monitoring sites across 16 counties

44,023 total readings (5yr window)

USGS NWIS

13

counties with a fresh pipeline snapshot

0 above13 below

State atlas notes

What stands out in Maine

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

Sagadahoc County has the highest value in the published state SDWIS Compliance Index table at 86.2/100, while Washington County has the lowest at 7.9/100. That is a 78.3 point gap inside one state.

Zero health violations

1

3+ health violations

15

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.

Kennebec County100.0%Knox County100.0%Lincoln County100.0%

Monitoring hubs

Washington County67 sitesAroostook County63 sitesYork County62 sites

Lowest flow reads

Waldo County0%Hancock County3%Lincoln County7%

Highest fresh streamflow pipeline snapshots: Oxford County (52%, observation 2026), Cumberland County (45%, observation 2026), Androscoggin County (41%, observation 2026). These are source-data observations, not household tap-water conclusions.

All Maine Counties

CountySDWIS Compliance Index
Sagadahoc County86.2
York County58.1
Cumberland County50.5
Androscoggin County47.9
Kennebec County47.9
Penobscot County38.3
Lincoln County28.9
Oxford County28.6
Somerset County23.5
Knox County22.7
Franklin County21.6
Aroostook County20.3
Hancock County10.8
Waldo County10.2
Piscataquis County9.7
Washington County7.9

Frequently Asked Questions

Which Maine county has the highest SDWIS Compliance Index?
Sagadahoc County has the highest SDWIS Compliance Index in the published Maine 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 Maine?
Across 9 published Maine county records with EPA ATTAINS data, 10 of 23 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 Maine?
WaterByCounty has 13 fresh USGS pipeline snapshots in the published Maine 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 Maine 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 Maine?
The published county records contain 44,023 results from 566 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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