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County water report

Navajo County Water Report

Drinking-water compliance, watershed health, monitoring records, and river conditions for Navajo County, Arizona.

Water grade

F

Water score

24.7

State rank

#9

of 15

Health violations

88

EPA SDWIS, 5-year lookback

Watershed impaired

4.2%

24 water bodies assessed

Monitoring sites

268

62,441 recent measurements

Live streamflow

2%

LITTLE COLORADO RIVER NEAR WINSLOW, AZ

Water at a glance

Key Water Indicators for Navajo County

EPA SDWIS

Safety Grade

F

Score: 24.7 / 100

EPA SDWIS

Active Violations

88

5-year health-based lookback

EPA ATTAINS

Watershed Health

4% impaired

24 bodies assessed

USGS NWIS

Streamflow Snapshot

2% of mean

LITTLE COLORADO RIVER NEAR WINSLOW, AZ

EPA WQP

Monitoring Sites

268

62,441 recent readings

Source: EPA SDWIS · Safe Drinking Water Information System

Drinking Water Compliance

Compliance grade

F

Based on EPA SDWIS compliance history.

Water score

Higher scores indicate cleaner recent compliance records.

24.7/100

Health violations

88

Health-based violations

Violations per 100K served

91.8

Population-normalized SDWIS rate

Editorial analysis

Understanding Navajo County’s Water

Drinking Water Quality Overview

EPA SDWIS

Navajo County's water systems carry a failing grade, scoring 24.7 out of 100. Over the past five years, EPA SDWIS records 88 health-based violations — a pattern that public water utilities are required to disclose and correct.

Watershed Conditions

EPA ATTAINS

Under the Clean Water Act §303(d), EPA ATTAINS tracks whether waterways meet quality standards for drinking, recreation, and aquatic life (reporting cycle: 2022). A small share — 4.2% — of assessed waterways are impaired (1 of 24 water bodies) across Navajo County's watersheds. The leading impairment cause is mercury in fish tissue. Impairment does not mean tap water is unsafe — it measures ambient waterway conditions upstream of treatment, not finished drinking water.

River & Streamflow Status

USGS NWIS

USGS NWIS gauge data (as of 2026-05-14T12:00:00.000-07:00) puts LITTLE COLORADO RIVER at 3.2 cfs — well below its long-term average at 2% of mean — low-flow conditions worth noting for water-dependent ecosystems. Streamflow is a leading indicator of drought stress, sediment load, and dilution capacity: low flows concentrate pollutants and warm water temperatures, stressing aquatic life and, in surface-water-dependent systems, the source water quality for treatment plants.

Monitoring Network

EPA WQP

EPA's Water Quality Portal (WQP) aggregates monitoring data from federal, state, and tribal agencies. Navajo County has extensive coverage with 268 active monitoring sites with 62,441 recent measurements on record. Predominant monitoring categories include organics, other and organics, pesticide. More monitoring sites generally indicate greater scientific attention to local water conditions — and provide the baseline data that regulators use to set future impairment listings.

Editorial advisory

What the data suggests for Navajo County

Water Verdict

Navajo County, Arizona 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. Separately, EPA ATTAINS assessments cover 24 water bodies in the county's watershed, with 4.2% listed as impaired under the Clean Water Act — a source-water measure that is tracked independently of tap-water compliance. At the most recent USGS reading, local streamflow was below its historical mean at 1.7% — worth watching in drier seasons.

Violation Context

EPA SDWIS records for Navajo County, Arizona show 88 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 91.8 violations per 100,000 people served, this rate is high and signals significant water quality management issues. This compliance record sits alongside an unusually deep monitoring archive: 62,441 water-quality results have been logged across the county in the EPA Water Quality Portal over the past five years.

Consumer Guidance

Navajo County has a Grade F compliance record with 88 health-based violations — among the highest levels in the country. Navajo County's drinking-water compliance score is 24.7 out of 100. The violation rate for Navajo County is 91.8 per 100,000 people served. Residents are strongly advised to use a certified NSF 58 reverse-osmosis filter or bottled water for all drinking and cooking until violations are corrected. Contacting the Arizona Department of Environmental Quality or Health can expedite utility compliance action. Mercury in Fish Tissue is the leading impairment cause in Navajo County's watershed. With 268 active water-quality monitoring sites in Navajo County, data coverage is strong. A pipeline streamflow snapshot from the LITTLE COLORADO RIVER gauge is also available on this page.

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.

Advisory text summarizes county-level public records and is not a replacement for your utility's current Consumer Confidence Report or direct local notices.

Contaminants & Resources

Key issues flagged in Navajo County's water environment

Watershed Impairment Causes (EPA ATTAINS)

  • 1

    Mercury (fish tissue)

    Impairment cause per EPA Clean Water Act §303(d) assessment

Source: EPA ATTAINS · Reporting cycle 2022

Official EPA Resources for Navajo County

EPA How's My Waterway

Interactive watershed health data for Navajo County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Navajo County

Consumer Confidence Reports (AZ)

Annual water quality reports from utilities in Arizona

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; the percent-of-typical value compares the latest reading against that average.

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Water Cost Estimate

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Annual Total

$558

Monthly

$47

Water Bill

$558/yr

Filter Cost

$0/yr

Safety Grade for Navajo County:C — Moderate

Some violations or watershed impairment detected.

Estimates use the national average residential water rate ($0.0068/gal, EPA/AWWA 2023) and EPA WaterSense per-person consumption baseline (75 gal/person/day). Actual bills vary by utility, usage tier, and local infrastructure fees. For informational purposes only.

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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 streamflow snapshots 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 has a pipeline snapshot of 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 the latest gauge feed, 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 and 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 Evan Brooks, Data EditorUpdated Reviewed by Evan Brooks, Data Editor

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