County water reports
Water Quality Reports for Every County
Search EPA compliance, watershed health, monitoring records, and live USGS streamflow in one county-level view.
Enter a county, state, district, or page name to search.
Compliance
EPA SDWIS
3,067
98% county coverage
Watersheds
EPA ATTAINS
1,922
61% county coverage
Monitoring
EPA WQP
2,975
95% county coverage
Streamflow
USGS NWIS
2,297
73% county coverage
Tracking water across 3,144 US counties · 51 states + DC
The Water Picture Your Utility Report Doesn't Show You
Every year, public water utilities mail a Consumer Confidence Report listing the contaminants they tested for. What those reports don't show is the broader picture: how your county's watersheds are doing, whether monitoring activity in your area is dense or sparse, and whether the rivers and streams that feed your reservoir are running low. WaterByCounty fills that gap by fusing four federal datasets — EPA SDWIS drinking-water compliance, EPA ATTAINS watershed health, EPA Water Quality Portal monitoring records, and USGS NWIS streamflow — into a single county-level view that anyone can read in under two minutes.
This site also fills a specific gap left when USGS WaterWatch, the longtime public dashboard for stream conditions across the US, was decommissioned at the end of 2025. WaterWatch gave millions of people a quick national picture of whether rivers were running high, low, or near normal. We carry that legacy forward at county resolution, pairing live NWIS streamflow against each gauge's long-term mean so you can see at a glance whether your county's primary waterway is above, at, or below typical levels for this time of year.
WaterByCounty is built for homebuyers researching a move, parents wondering about school water quality, journalists covering infrastructure, and policy researchers comparing compliance across jurisdictions. The data comes entirely from public federal sources — no proprietary scoring, no paywalls. Every number links back to an EPA or USGS endpoint you can verify yourself.
Edited by Evan Brooks, Data Editor. Editorial standards.
Four sources, one county view
The report separates tap water, watershed health, monitoring depth, and flow.
We normalize each source to the county level and surface the data that is actually reported. Drinking-water grades stay tied to EPA compliance; the other layers add context instead of pretending to be the same measurement.
Drinking Water Compliance
EPA SDWISHealth-based violations and quality grades from the Safe Drinking Water Information System. 5-year violation lookback.
3,067
98% coverage
Watershed Health
EPA ATTAINSImpaired-waterway assessments under Clean Water Act §303(d), including what share of water bodies fail state standards and why.
1,922
61% coverage
Monitoring Records
EPA WQPCounts of water-quality monitoring sites and measurements from the federal Water Quality Portal, rolling 5-year window.
2,975
95% coverage
Streamflow Snapshot
USGS NWISLatest pipeline reading from the primary streamgage per county, compared against the long-term mean to flag rivers running high or low.
2,297
73% coverage
Greenville County
South Carolina
Water Quality Grade
A
Quality Grade
A
Quality Score
71.8
Health Violations (5yr)
1
Violations / 100K Served
0.2 / 100K served
EPA ATTAINS · Clean Water Act §303(d)
Watershed Health Spotlight
Counties on opposite ends of the watershed-impairment spectrum, ranked by the share of assessed water bodies that fail Clean Water Act §303(d) quality standards.
Cleanest assessed watersheds
Minimum 8 assessed water bodies required for ranking inclusion to avoid distortion from small samples. Counties without ATTAINS assessments are not eligible.
USGS NWIS · Live streamgages
Rivers Running Far From Typical
Counties whose primary streamgage is currently flowing well above or well below its long-term mean. Useful for flood watch, drought signal, and source-water context.
Running well above typical
Snapshot from the most recent USGS reading per county. Refreshed on the next data sync.
Interactive Water Intelligence Tools
Explore, compare, and analyze water data across all 3,100+ US counties: compliance, watershed health, monitoring records, and streamflow snapshots.
National Insights
Aggregated views: state rankings, impairment distribution, monitoring coverage, and streamflow patterns.
See InsightsWater Restrictions
City watering rules, schedules, allowed hours, and compliant lawn-watering guides.
Check Local RulesGrade Breakdown
A–F letter grades for every county based on EPA SDWIS compliance and violation data.
Explore by StateWater Articles
Data-driven articles on drinking water, watersheds, monitoring, and home filtration.
Browse ArticlesWater Quality Guides & Analysis
Data-driven articles on drinking water quality and safety across America.
Article
Understanding Drinking Water Quality by County
A data-driven analysis of drinking water quality across all US counties. How EPA SDWIS data reveals geographic patterns, grade distributions, and what drives water quality differences.
Article
EPA Water Violations: What They Mean for Your Tap Water
What EPA drinking water violations actually mean, the different types of violations, which counties have the most, and what you can do if your county has a low water quality score.
Article
Best and Worst Counties for Water Quality in America
The 25 best and 25 worst counties for drinking water quality in the United States, ranked by EPA compliance data. Geographic patterns, common factors, and what it means for residents.
Article
Rural vs Urban Water Quality by County
How drinking water quality differs between rural and urban counties in America. Comparing EPA compliance data, population-normalized violation rates, and scores by county characteristics.
Article
Water Quality Grade Distribution Across US Counties
How many US counties earn A, B, C, D, or F grades for drinking water quality? A complete breakdown of the national grade distribution using EPA SDWIS data.
How We Grade Drinking Water
Letter grades are computed from EPA SDWIS compliance history. Watershed health, monitoring density, and streamflow are reported separately, not folded into the grade.
A
Excellent
Score: 90–100
B
Good
Score: 75–89
C
Moderate
Score: 60–74
D
Poor
Score: 40–59
F
Failing
Score: Below 40
Browse by State
Select a state to view water quality data for every county.
Alabama
67 counties
68.8
Alaska
30 counties
19.8
Arizona
15 counties
28.6
Arkansas
75 counties
47.6
California
58 counties
44.6
Colorado
64 counties
38.7
Connecticut
9 counties
N/A
Delaware
3 counties
66.1
District of Columbia
1 county
69.3
Florida
67 counties
56.0
Georgia
159 counties
64.4
Hawaii
5 counties
78.6
Idaho
44 counties
32.6
Illinois
102 counties
47.8
Indiana
92 counties
52.5
Iowa
99 counties
71.7
Kansas
105 counties
42.6
Kentucky
120 counties
64.2
Louisiana
64 counties
30.1
Maine
16 counties
30.1
Maryland
24 counties
50.5
Massachusetts
14 counties
69.1
Michigan
83 counties
58.5
Minnesota
87 counties
67.2
Mississippi
82 counties
51.7
Missouri
115 counties
48.8
Montana
56 counties
48.9
Nebraska
93 counties
58.1
Nevada
17 counties
48.5
New Hampshire
10 counties
33.2
New Jersey
21 counties
55.7
New Mexico
33 counties
21.7
New York
62 counties
40.1
North Carolina
100 counties
53.0
North Dakota
53 counties
71.6
Ohio
88 counties
56.2
Oklahoma
77 counties
15.8
Oregon
36 counties
44.6
Pennsylvania
67 counties
38.9
Rhode Island
5 counties
65.0
South Carolina
46 counties
64.9
South Dakota
66 counties
56.8
Tennessee
95 counties
71.3
Texas
254 counties
30.4
Utah
29 counties
47.7
Vermont
14 counties
45.6
Virginia
133 counties
57.7
Washington
39 counties
59.3
West Virginia
55 counties
35.2
Wisconsin
72 counties
39.5
Wyoming
23 counties
36.6
Best Water Quality Counties
Counties with the highest water quality scores.
Why a Multi-Source Picture Matters
No single dataset tells the full story. Compliance can be clean while the watershed is impaired. Streamflow can be normal while monitoring is sparse. WaterByCounty layers all four signals.
What comes out of the tap
EPA SDWIS records health-based violations of the Safe Drinking Water Act. A clean record means your public water system met federal standards; it does not speak to source water.
The watershed itself
EPA ATTAINS, under the Clean Water Act §303(d), classifies water bodies as impaired when they fail state quality standards. A high impairment % is a warning even when tap-water grades look fine.
How much is actually measured
The EPA Water Quality Portal aggregates monitoring records from federal, state, and tribal sources. More sites and readings = more scientific confidence in whatever signal you see.
What the rivers are doing right now
USGS streamgages report live discharge. A river running well below typical signals drought stress on source water; well above typical can mean storm runoff entering treatment facilities.