waterbycounty
Federal water data

Connecticut Water Quality

Drinking water data for all 9 counties.

Avg Water Score

N/A

State Grade

N/A

Counties with Data

0

of 9 total

County water atlas

Connecticut 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 isolate clean systems, violation clusters, or impaired watersheds without leaving the page.

Counties

9

Avg score

Pending

Watersheds

5

ATTAINS counties

Monitoring

0

9 gauges

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 are pipeline snapshots, not a real-time stream. County pages include the source-specific detail behind each layer.

Multi-source coverage in Connecticut

Beyond Drinking Water

EPA SDWIS

0/ 9

counties with drinking-water compliance data

EPA ATTAINS

60.0%

avg impaired across 5 counties

8 of 12 assessed bodies impaired

EPA WQP

—

No WQP monitoring data in this state

USGS NWIS

9

counties with an active streamgage

0 above8 below

State atlas notes

What stands out in Connecticut

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

EPA SDWIS coverage is present for 0 Connecticut counties, but the score spread is still stabilizing.

Zero health violations

0

3+ health violations

0

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.

Naugatuck Valley Planning Region100.0%Capitol Planning Region66.7%Lower Connecticut River Valley Planning Region66.7%

Lowest flow reads

Naugatuck Valley Planning Region18%Greater Bridgeport Planning Region22%South Central Connecticut Planning Region51%

Highest current streamflow readings: Lower Connecticut River Valley Planning Region (110%), Western Connecticut Planning Region (80%), Capitol Planning Region (79%). High flow can reflect recent storms or runoff, not necessarily safer source water.

All Connecticut Counties

CountyWater Score
Capitol Planning Region—
Greater Bridgeport Planning Region—
Lower Connecticut River Valley Planning Region—
Naugatuck Valley Planning Region—
Northeastern Connecticut Planning Region—
Northwest Hills Planning Region—
South Central Connecticut Planning Region—
Southeastern Connecticut Planning Region—
Western Connecticut Planning Region—

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Frequently Asked Questions

Which county in Connecticut has the best water quality?
See the county rankings below for drinking-water compliance across Connecticut.
Which county in Connecticut has the most water violations?
See the county rankings below for drinking-water compliance data across Connecticut.
How healthy are Connecticut's watersheds?
Across the 5 Connecticut counties with EPA ATTAINS §303(d) assessments, an average of 60.0% of assessed water bodies are classified as impaired — 8 of 12 reported assessments. Impairment is a Clean Water Act designation that a water body fails to meet state quality standards for one or more designated uses.
What are streams and rivers doing across Connecticut right now?
Of the 9 Connecticut counties with an active USGS streamgage, 0 are currently flowing above their long-term mean and 8 are flowing below. Above-typical can indicate recent storm runoff; below-typical can indicate drought stress on source water. See each county page for the specific gauge and reading.
Is the tap water safe to drink in Connecticut?
Drinking-water compliance data for Connecticut counties is available in the table below. Always check your local water utility's Consumer Confidence Report for the most current data.
What contaminants are tracked in Connecticut water supplies?
EPA SDWIS tracks violations for regulated contaminants like lead, nitrates, bacteria, disinfection byproducts, and others. EPA ATTAINS captures broader watershed impairments including mercury, E. coli, sediment, nutrients, and PCBs. The Water Quality Portal aggregates monitoring records from federal, state, and tribal sources. See individual county pages for source-specific detail.
What's the difference between SDWIS, ATTAINS, WQP, and NWIS?
Each one measures a different layer of water. EPA SDWIS tracks drinking-water compliance — whether your public water system met federal Safe Drinking Water Act standards. EPA ATTAINS records §303(d) assessments — what share of a county's rivers, lakes, and streams fail state quality standards under the Clean Water Act. EPA WQP aggregates monitoring records — how many samples have been taken and what's being measured. USGS NWIS provides streamflow snapshots — how much water was flowing through the county's primary streamgage when the pipeline last ran. SDWIS speaks to your tap; the other three speak to source water and the watershed.
What does it mean when a water body is impaired?
An 'impaired' designation under Clean Water Act §303(d) means the state has determined the water body fails to meet its designated-use quality standards — drinking water source, recreation, aquatic life, or fish consumption — for one or more pollutants. Top causes nationally include mercury, E. coli (and other fecal indicator bacteria), nutrients, sediment, and PCBs. Impairment is a structural signal about the watershed, not necessarily about what comes out of your tap (treatment plants can remove or reduce contaminants before delivery).

Data Sources

Drinking-water compliance data from the EPA Safe Drinking Water Information System (SDWIS) via the ECHO enforcement database. Scores reflect compliance history and health-based violation counts.

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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