waterbycounty
EPA SDWIS

Fresno County Water Quality

Fresno County, California

Water Grade

C

Water Score

52.5

Violations

128

State Rank

#21

of 58 (1 = best)

EPA SDWIS Compliance

Drinking Water Quality

Water Quality Grade

C

Based on EPA compliance history and violation data

Water Score

52.5/100

Higher = better quality

Health Violations

128

Health-based violations

Violation Rate

13.0%

Systems with violations

Water Advisory: Fresno County

Water Verdict

Fresno County receives a below-average water quality assessment with a grade of C and a score of 52.5 out of 100. Residents should review their utility's Consumer Confidence Report and may want to consider additional water filtration for drinking.

Violation Context

Fresno County has recorded 128 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 13.0 violations per 1,000 residents, this rate is high and signals significant water quality management issues.

Consumer Guidance

Tap water in Fresno County meets baseline standards, but residents who are immunocompromised or have young children may want to use an NSF-certified water filter as a precaution. With 128 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

Fresno County has better water quality than the average county in California. Its water score is 7.9 points higher than the state average, indicating stronger water system performance relative to neighboring counties.

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

24.7%

23 of 93 assessed

Some impairment

Top Impairment Causes

  • 1

    TOXICITY

  • 2

    PH

  • 3

    ALKALINITY

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

30

Active in the past 5 years

Measurements Recorded

5.6K

5,568 total readings

Most Measured

  • Organics, Pesticide
  • Organics, Other
  • Inorganics, Minor, Metals

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

153cfs

Dec 9, 8:00 AM UTC

vs Long-Term Average

20%

Well below typical

Primary Streamgage

SAN JOAQUIN R NR MENDOTA CA

USGS site
11254000
Drainage area
3,940 sq mi
Long-term mean
764 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 Fresno County, California?
Fresno County, California has a drinking-water quality grade of C with a score of 52.5/100, based on EPA SDWIS compliance data. The county has 128 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 Fresno County?
Fresno County has 128 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 Fresno County?
EPA ATTAINS assessments under Clean Water Act §303(d) indicate 24.7% of Fresno County's 93 assessed water bodies are classified as impaired (23 impaired). The top reported causes are TOXICITY, PH, ALKALINITY. 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 Fresno County?
EPA's Water Quality Portal records 5,568 measurements from 30 monitoring sites in Fresno County over the past five years. The most frequently measured characteristic groups are Organics, Pesticide, Organics, Other, Inorganics, Minor, Metals. 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 Fresno County right now?
Fresno County's primary USGS streamgage on the SAN JOAQUIN R is currently reading 153 cubic feet per second — 20% of the long-term mean of 763.91 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 Fresno County water compare to the California average?
Fresno County's SDWIS water quality score of 52.5/100 is higher than the California state average of 44.6. The average water quality grade across California is D, based on data from 58 counties with available SDWIS data.
Is tap water safe to drink in Fresno County?
Based on EPA SDWIS data, Fresno County has a water quality grade of C (52.5/100). This indicates moderate compliance. Some violations have been recorded but overall standards are maintained. 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 Fresno County have so many water violations?
Fresno County has 128 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 Fresno County rank for water quality in California?
Fresno County ranks #21 out of 58 counties in California by SDWIS water quality score (1 = best). With a score of 52.5/100, 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

San Bernardino County

California

C

52.3

Water score

Santa Cruz County

California

D

50.6

Water score

Lassen County

California

C

54.6

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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