County water report

Williamson County Water Report

Drinking-water compliance, watershed health, monitoring records, and river conditions for Williamson County, Texas.

Water grade

Water score

66.5

State rank

#21

of 254

Health violations

EPA SDWIS, 5-year lookback

Watershed impaired

Not reported

EPA ATTAINS coverage varies by state

Monitoring sites

12,446 recent measurements

Live streamflow

121%

San Gabriel Rv at Laneport, TX

Water at a glance

Key Water Indicators for Williamson County

EPA SDWIS

Safety Grade

Score: 66.5 / 100

EPA SDWIS

Active Violations

5-year health-based lookback

EPA ATTAINS

Watershed Health

Not reported

Coverage varies by state

USGS NWIS

Streamflow Snapshot

121% of mean

San Gabriel Rv at Laneport, TX

EPA WQP

Monitoring Sites

12,446 recent readings

Source: EPA SDWIS · Safe Drinking Water Information System

Drinking Water Compliance

Compliance grade

Based on EPA SDWIS compliance history.

Water score

Higher scores indicate cleaner recent compliance records.

66.5/100

Health violations

Health-based violations

Violations per 100K served

2.7

Population-normalized SDWIS rate

Data center water stress

Williamson County has 1 facility in the DCWSI dataset.

ByCounty's DCWSI ranks this county #1110 nationally by combining its water score with mapped data center density.

DCWSI

39.9

0-100 index

Facility count

0.0 density percentile

Discharge estimate

Not reported

EPA CWA fields where available

Water vs median

+16.5

Compared with US county median

Named operators

Switch

Mapped facilities

Switch: The Rock
Switch
OSM

See the Williamson County data-center report Review methodology

Data Center Water Budget Calculator

Estimate daily water use for a hypothetical facility in Williamson County.

Facility size: 100 MW

1 MW1,000 MW

Cooling type

Utilization: 70%

40%100%

799K gallons/dayHigh Impact

Your facility would use 97.5% of this county's industrial water baseline. Verify water rights and long-term drought projections before committing.

97.5% of county industrial baseline0.02 Mgal/day remaining headroom

Based on USGS 2020 water-use data and EPA-standard cooling intensity constants. Not a substitute for site-specific water rights analysis.

Editorial analysis

Understanding Williamson County’s Water

Drinking Water Quality Overview

EPA SDWIS

Williamson County earns a B grade for drinking water quality, scoring 66.5 out of 100. Over the past five years, EPA SDWIS records 19 health-based violations — a pattern that public water utilities are required to disclose and correct.

River & Streamflow Status

USGS NWIS

USGS NWIS gauge data (as of 2026-05-14T13:15:00.000-05:00) puts San Gabriel Rv at 285.0 cfs — flowing above its historical average at 121% of mean. 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. Williamson County has moderate coverage with 41 active monitoring sites with 12,446 recent measurements on record. Predominant monitoring categories include physical and inorganics, major, non-metals. 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 Williamson County

Water Verdict

Williamson County, Texas 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. The county's primary USGS gauge drains roughly 738 square miles of upstream watershed, giving local source waters a regional footprint. At the most recent USGS reading, local streamflow was running above its historical mean at 121.2%.

Violation Context

EPA SDWIS records for Williamson County, Texas show 19 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 2.7 violations per 100,000 people served, this rate is relatively low compared to many U.S. counties. This compliance record sits alongside an unusually deep monitoring archive: 12,446 water-quality results have been logged across the county in the EPA Water Quality Portal over the past five years.

Consumer Guidance

Tap water in Williamson County meets baseline safety standards, though the compliance record shows some violations worth watching. Williamson County's drinking-water compliance score is 66.5 out of 100. The violation rate for Williamson County is 2.7 per 100,000 people served. Running tap water for 30 seconds before drinking can reduce any localized lead exposure from household plumbing. Requesting your utility's most recent Consumer Confidence Report is the fastest way to identify which specific contaminants were flagged. With 41 active water-quality monitoring sites in Williamson County, data coverage is strong. A pipeline streamflow snapshot from the San Gabriel Rv gauge is also available on this page.

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.

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 Williamson County's water environment

Official EPA Resources for Williamson County

EPA How's My Waterway

Interactive watershed health data for Williamson County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Williamson County

Consumer Confidence Reports (TX)

Annual water quality reports from utilities in Texas

Past 5 years

Water Quality Monitoring

Monitoring Sites

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

Free tool

Estimate Your Water Costs

Water Cost Estimate

Household size

3 people · ~225 gal/day

Filter type

Annual Total

$558

Monthly

$47

Water Bill

$558/yr

Filter Cost

$0/yr

Safety Grade for Williamson 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 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 streamflow snapshots 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 has a pipeline snapshot of 285 cubic feet per second — 121% of the long-term mean of 235.24 cfs. Flow is within typical range for this gauge. For the latest gauge feed, 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

66.8

Water score

Rockwall County

Texas

66.8

Water score

Harris County

Texas

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 Evan Brooks, Data EditorUpdated May 14, 2026Reviewed by Evan Brooks, Data Editor

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