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County water report

Cowlitz County Water Report

Drinking-water compliance, watershed health, monitoring records, and river conditions for Cowlitz County, Washington.

Water grade

B

Water score

66.4

State rank

#15

of 39

Health violations

3

EPA SDWIS, 5-year lookback

Watershed impaired

Not reported

EPA ATTAINS coverage varies by state

Monitoring sites

6

10,657 recent measurements

Live streamflow

79%

COWLITZ RIVER AT CASTLE ROCK, WA

Water at a glance

Key Water Indicators for Cowlitz County

EPA SDWIS

Safety Grade

B

Score: 66.4 / 100

EPA SDWIS

Active Violations

3

5-year health-based lookback

EPA ATTAINS

Watershed Health

Not reported

Coverage varies by state

USGS NWIS

Streamflow Snapshot

79% of mean

COWLITZ RIVER AT CASTLE ROCK, WA

EPA WQP

Monitoring Sites

6

10,657 recent readings

Source: EPA SDWIS · Safe Drinking Water Information System

Drinking Water Compliance

Compliance grade

B

Based on EPA SDWIS compliance history.

Water score

Higher scores indicate cleaner recent compliance records.

66.4/100

Health violations

3

Health-based violations

Violations per 100K served

2.8

Population-normalized SDWIS rate

Editorial analysis

Understanding Cowlitz County’s Water

Drinking Water Quality Overview

EPA SDWIS

Cowlitz County earns a B grade for drinking water quality, scoring 66.4 out of 100. Over the past five years, EPA SDWIS records 3 health-based violations — a small cluster that warrants attention.

River & Streamflow Status

USGS NWIS

USGS NWIS gauge data (as of 2026-05-14T11:30:00.000-07:00) puts COWLITZ RIVER at 7.2k cfs — running somewhat below its historical average at 79% 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. Cowlitz County has limited coverage with 6 active monitoring sites with 10,657 recent measurements on record. Predominant monitoring categories include physical and sediment. 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 Cowlitz County

Water Verdict

Cowlitz County, Washington receives a fair water quality assessment with a grade of B and a score of 66.4 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 2,238 square miles of upstream watershed, giving local source waters a regional footprint. At the most recent USGS reading, local streamflow was below its historical mean at 78.5% — worth watching in drier seasons.

Violation Context

EPA SDWIS records for Cowlitz County, Washington show 3 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 2.8 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: 10,657 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 Cowlitz County scores well above average for drinking-water safety. Cowlitz County's drinking-water compliance score is 66.4 out of 100. With 3 recorded health violations, the water supply is generally reliable. The violation rate for Cowlitz County is 2.8 per 100,000 people served. Households with infants, pregnant individuals, or immunocompromised members may want to use an NSF 53-certified pitcher filter as a low-cost precaution. There are 6 active water-quality monitoring sites in Cowlitz County. A pipeline streamflow snapshot from the COWLITZ RIVER gauge is also available on this page.

Regional Context

Cowlitz County has better water quality than the average county in Washington. Its water score is 7.1 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 Cowlitz County's water environment

Official EPA Resources for Cowlitz County

EPA How's My Waterway

Interactive watershed health data for Cowlitz County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Cowlitz County

Consumer Confidence Reports (WA)

Annual water quality reports from utilities in Washington

Past 5 years

Water Quality Monitoring

Monitoring Sites

6

Active in the past 5 years

Measurements Recorded

11K

10,657 total readings

Most Measured

  • Physical
  • Sediment
  • 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

7,190cfs

May 14, 6:30 PM UTC

vs Long-Term Average

79%

Below typical

Primary Streamgage

COWLITZ RIVER AT CASTLE ROCK, WA

USGS site
14243000
Drainage area
2,238 sq mi
Long-term mean
9,162 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

3

3 people  ·  ~225 gal/day

Annual Total

$558

Monthly

$47

Water Bill

$558/yr

Filter Cost

$0/yr

Safety Grade for Cowlitz 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 Cowlitz County, Washington?
Cowlitz County, Washington has a drinking-water quality grade of B with a score of 66.4/100, based on EPA SDWIS compliance data. The county has 3 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 Cowlitz County?
Cowlitz County has 3 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 Cowlitz County?
EPA's Water Quality Portal records 10,657 measurements from 6 monitoring sites in Cowlitz County over the past five years. The most frequently measured characteristic groups are Physical, Sediment, 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 Cowlitz County right now?
Cowlitz County's primary USGS streamgage on the COWLITZ RIVER has a pipeline snapshot of 7,190 cubic feet per second — 79% of the long-term mean of 9,161.94 cfs. Flow is within typical range for this gauge. For the latest gauge feed, visit waterdata.usgs.gov.
How does Cowlitz County water compare to the Washington average?
Cowlitz County's SDWIS water quality score of 66.4/100 is higher than the Washington state average of 59.3. The average water quality grade across Washington is D, based on data from 39 counties with available SDWIS data.
Is tap water safe to drink in Cowlitz County?
Based on EPA SDWIS data, Cowlitz County has a water quality grade of B (66.4/100). 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).
Does Cowlitz County have clean drinking water?
Cowlitz County has 3 health-based drinking water violations according to EPA records. With a water quality score of 66.4/100 and grade B, the county's drinking water has had some compliance issues but continues to be monitored. Note: drinking-water compliance speaks to the public water system, not necessarily to the watershed itself — check the Watershed Health zone for ATTAINS §303(d) data.
How does Cowlitz County rank for water quality in Washington?
Cowlitz County ranks #15 out of 39 counties in Washington by SDWIS water quality score (1 = best). With a score of 66.4/100, 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

Kittitas County

Washington

B

66.4

Water score

Kitsap County

Washington

B

67.5

Water score

Skagit County

Washington

B

65.3

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 Reviewed by Evan Brooks, Data Editor

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