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EPA SDWIS

Navajo County Water Quality

Navajo County, Arizona

Water Grade

F

Water Score

24.7

Violations

88

State Rank

#9

of 15 (1 = best)

EPA SDWIS Compliance

Drinking Water Quality

Water Quality Grade

F

Based on EPA compliance history and violation data

Water Score

24.7/100

Higher = better quality

Health Violations

88

Health-based violations

Violation Rate

91.8%

Systems with violations

Water Advisory: Navajo County

Water Verdict

Navajo County receives a poor water quality assessment with a grade of F and a score of 24.7 out of 100. The water supply has documented quality issues. Residents are strongly encouraged to use filtered or bottled water for drinking and to stay informed about utility improvement plans.

Violation Context

Navajo County has recorded 88 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 91.8 violations per 1,000 residents, this rate is high and signals significant water quality management issues.

Consumer Guidance

Residents of Navajo County are advised to use filtered or bottled water for drinking and cooking until water quality improves. A reverse-osmosis or activated-carbon filter certified to remove the contaminants listed in the utility's Consumer Confidence Report is recommended. With 88 recorded health violations, staying informed about utility communications and boil-water notices is especially important. For long-term peace of mind, request your utility's latest Consumer Confidence Report and consider independent water testing if you have specific health concerns.

Regional Context

Navajo County has water quality close to the average county in Arizona. Its water score is within 3.9 points of the state average, meaning its overall water system performance is broadly representative of Arizona as a whole.

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

4.2%

1 of 24 assessed

Mostly healthy

Top Impairment Causes

  • 1

    MERCURY IN FISH TISSUE

Source: EPA ATTAINS · Reporting cycle 2022

Impairment is determined under the Clean Water Act §303(d): a water body is impaired when it fails to meet state-defined quality standards for designated uses (drinking, recreation, aquatic life). Assessment coverage varies by state — counties without assessed water bodies are not shown.

Past 5 years

Water Quality Monitoring

Monitoring Sites

268

Active in the past 5 years

Measurements Recorded

62K

62,441 total readings

Most Measured

  • Organics, Other
  • Organics, Pesticide
  • Physical

Categories measured most frequently

Data from the EPA Water Quality Portal (WQP), aggregating monitoring records from federal, state, and tribal sources. Each measurement represents a single sample analyzed for a specific characteristic (e.g., E. coli, pH, dissolved oxygen, nitrogen).

Live USGS Streamgage

River & Stream Conditions

Current Discharge

3.23cfs

May 14, 7:00 PM UTC

vs Long-Term Average

2%

Well below typical

Primary Streamgage

LITTLE COLORADO RIVER NEAR WINSLOW, AZ

USGS site
09400350
Drainage area
16,192 sq mi
Long-term mean
192 cfs

One representative streamgage (the one with the largest drainage area in the county). Many counties have multiple gauges — this view summarizes the primary one. The long-term mean is the full-record annual average; "% of typical" compares the latest reading against that average.

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Frequently Asked Questions

What is the water quality in Navajo County, Arizona?
Navajo County, Arizona has a drinking-water quality grade of F with a score of 24.7/100, based on EPA SDWIS compliance data. The county has 88 health-based drinking water violations over the past 5 years. Watershed health, monitoring records, and live streamflow are reported separately on this page.
Are there any water violations in Navajo County?
Navajo County has 88 health-based drinking water violations recorded by the EPA over the past 5 years. Health-based violations indicate instances where contaminant levels exceeded EPA Maximum Contaminant Levels (MCLs). Violations may have been resolved — check with your local water utility for current status.
How healthy are the watersheds in Navajo County?
EPA ATTAINS assessments under Clean Water Act §303(d) indicate 4.2% of Navajo County's 24 assessed water bodies are classified as impaired (1 impaired). The top reported causes are MERCURY IN FISH TISSUE. Impairment means the water body fails to meet state quality standards for at least one designated use — drinking water source, recreation, aquatic life, or fish consumption. Note: watershed impairment doesn't always translate to tap-water issues; treatment plants can remove most regulated contaminants.
How much water-quality monitoring happens in Navajo County?
EPA's Water Quality Portal records 62,441 measurements from 268 monitoring sites in Navajo County over the past five years. The most frequently measured characteristic groups are Organics, Other, Organics, Pesticide, Physical. Each measurement is a single sample analyzed for one characteristic (E. coli, pH, dissolved oxygen, etc.). High monitoring density means more scientific evidence behind any reported signal — it does not by itself indicate water quality.
What's happening with rivers in Navajo County right now?
Navajo County's primary USGS streamgage on the LITTLE COLORADO RIVER is currently reading 3.23 cubic feet per second — 2% of the long-term mean of 192.05 cfs. This is well below typical — often a signal of drought stress on source water. For genuine real-time data, visit waterdata.usgs.gov.
How does Navajo County water compare to the Arizona average?
Navajo County's SDWIS water quality score of 24.7/100 is lower than the Arizona state average of 28.6. The average water quality grade across Arizona is F, based on data from 15 counties with available SDWIS data.
Is tap water safe to drink in Navajo County?
Based on EPA SDWIS data, Navajo County has a water quality grade of F (24.7/100). This indicates below-average compliance with significant violations. Residents may want to consider home water filtration or independent testing. The grade speaks to the public water system, not the watershed — for watershed-level concerns, see the Watershed Health zone. For the most up-to-date information, contact your local water utility or review your Consumer Confidence Report (CCR).
Why does Navajo County have so many water violations?
Navajo County has 88 health-based drinking water violations on record from the EPA SDWIS database. A higher violation count can result from aging infrastructure, underfunded water utilities, agricultural runoff contamination, or industrial pollution. Counties with more water systems may also see more violations simply due to scale. Residents concerned about water quality should consider independent water testing and home filtration systems.
How does Navajo County rank for water quality in Arizona?
Navajo County ranks #9 out of 15 counties in Arizona by SDWIS water quality score (1 = best). With a score of 24.7/100, it falls in the middle third of counties statewide. The ranking reflects EPA SDWIS compliance only — not watershed impairment, monitoring density, or streamflow, which are tracked separately on this page.

Counties with Similar Water Quality

Mohave County

Arizona

F

26.2

Water score

Cochise County

Arizona

F

21.7

Water score

Pinal County

Arizona

F

30.4

Water score

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.

Watershed health and impaired-waterway data from the EPA ATTAINS Clean Water Act §303(d) assessments — state-reported, EPA-finalized.

Water-quality monitoring counts from the EPA Water Quality Portal (WQP) — federated USGS, EPA, and state agency sampling records over a rolling 5-year window.

Live streamflow from the USGS National Water Information System (NWIS) — continuous discharge measurements from the largest-drainage gauge in each county, compared against the full-record long-term annual mean.

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.

By Logan Johnson, Founder & Data EditorUpdated Reviewed by Logan Johnson, Founder & Data Editor

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