waterbycounty
EPA SDWIS

Williamson County Water Quality

Williamson County, Texas

Water Grade

B

Water Score

66.5

Violations

19

State Rank

#21

of 254 (1 = best)

EPA SDWIS Compliance

Drinking Water Quality

Water Quality Grade

B

Based on EPA compliance history and violation data

Water Score

66.5/100

Higher = better quality

Health Violations

19

Health-based violations

Violation Rate

2.7%

Systems with violations

Water Advisory: Williamson County

Water Verdict

Williamson County receives a fair water quality assessment with a grade of B and a score of 66.5 out of 100. The water supply meets baseline federal standards, but there may be periods of elevated contaminant levels or infrastructure concerns worth monitoring.

Violation Context

Williamson County has recorded 19 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 2.7 violations per 1,000 residents, this rate is relatively low compared to many U.S. counties.

Consumer Guidance

Tap water in Williamson County is generally safe to drink based on available data. Residents should still review their utility's annual Consumer Confidence Report for transparency on detected contaminants. With 19 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

Williamson County has better water quality than the average county in Texas. Its water score is 36.1 points higher than the state average, indicating stronger water system performance relative to neighboring counties.

Past 5 years

Water Quality Monitoring

Monitoring Sites

41

Active in the past 5 years

Measurements Recorded

12K

12,446 total readings

Most Measured

  • Physical
  • Inorganics, Major, Non-metals
  • Nutrient

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

285cfs

May 14, 6:15 PM UTC

vs Long-Term Average

121%

Above typical

Primary Streamgage

San Gabriel Rv at Laneport, TX

USGS site
08105700
Drainage area
738 sq mi
Long-term mean
235 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 Williamson County, Texas?
Williamson County, Texas has a drinking-water quality grade of B with a score of 66.5/100, based on EPA SDWIS compliance data. The county has 19 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 Williamson County?
Williamson County has 19 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 much water-quality monitoring happens in Williamson County?
EPA's Water Quality Portal records 12,446 measurements from 41 monitoring sites in Williamson County over the past five years. The most frequently measured characteristic groups are Physical, Inorganics, Major, Non-metals, Nutrient. 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 Williamson County right now?
Williamson County's primary USGS streamgage on the San Gabriel Rv is currently reading 285 cubic feet per second — 121% of the long-term mean of 235.24 cfs. Flow is within typical range for this gauge. For genuine real-time data, visit waterdata.usgs.gov.
How does Williamson County water compare to the Texas average?
Williamson County's SDWIS water quality score of 66.5/100 is higher than the Texas state average of 30.4. The average water quality grade across Texas is F, based on data from 254 counties with available SDWIS data.
Is tap water safe to drink in Williamson County?
Based on EPA SDWIS data, Williamson County has a water quality grade of B (66.5/100). This indicates good to excellent water quality with strong SDWIS compliance. 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 Williamson County have so many water violations?
Williamson County has 19 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 Williamson County rank for water quality in Texas?
Williamson County ranks #21 out of 254 counties in Texas by SDWIS water quality score (1 = best). With a score of 66.5/100, it falls in the top 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

Denton County

Texas

B

66.8

Water score

Rockwall County

Texas

B

66.8

Water score

Harris County

Texas

B

65.8

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.

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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