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St. Charles County Water Report

Drinking-water compliance, watershed health, monitoring records, and river conditions for St. Charles County, Missouri.

Water grade

A

Water score

86.0

State rank

#29

of 115

Health violations

0

EPA SDWIS, 5-year lookback

Watershed impaired

Not reported

EPA ATTAINS coverage varies by state

Monitoring sites

36

4,057 recent measurements

Live streamflow

3%

Dardenne Creek at Old Town St. Peters, MO

Water at a glance

Key Water Indicators for St. Charles County

EPA SDWIS

Safety Grade

A

Score: 86.0 / 100

EPA SDWIS

Active Violations

0

5-year health-based lookback

EPA ATTAINS

Watershed Health

Not reported

Coverage varies by state

USGS NWIS

Streamflow Snapshot

3% of mean

Dardenne Creek at Old Town St. Peters, MO

EPA WQP

Monitoring Sites

36

4,057 recent readings

Source: EPA SDWIS · Safe Drinking Water Information System

Drinking Water Compliance

Compliance grade

A

Based on EPA SDWIS compliance history.

Water score

Higher scores indicate cleaner recent compliance records.

86.0/100

Health violations

0

Health-based violations

Violations per 100K served

0.0

Population-normalized SDWIS rate

Editorial analysis

Understanding St. Charles County’s Water

Drinking Water Quality Overview

EPA SDWIS

St. Charles County earns an A grade for drinking water quality, scoring 86.0 out of 100. EPA's Safe Drinking Water Information System (SDWIS) records zero health-based violations over the past five years — a strong compliance signal for a mid-sized county.

River & Streamflow Status

USGS NWIS

USGS NWIS gauge data (as of 2026-05-14T14:00:00.000-05:00) puts Dardenne Creek at 3.2 cfs — well below its long-term average at 3% 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. St. Charles County has moderate coverage with 36 active monitoring sites with 4,057 recent measurements on record. Predominant monitoring categories include physical and nutrient. 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 St. Charles County

Water Verdict

St. Charles County, Missouri receives an excellent water quality assessment with a grade of A and a score of 86.0 out of 100. The water supply meets or exceeds federal safety standards, and residents can generally drink tap water with confidence. The county's primary USGS gauge drains roughly 102 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 2.7% — worth watching in drier seasons.

Violation Context

EPA SDWIS records for St. Charles County, Missouri show zero health-based violations, indicating that the county's water systems met all federal safety standards during the reporting period. The violation rate is zero per 100,000 people served, which is the best possible outcome. For independent context, 4,057 water-quality monitoring results have been recorded across the county in the EPA Water Quality Portal over the past five years.

Consumer Guidance

Tap water in St. Charles County is safe to drink based on current EPA compliance records. No health-based violations have been recorded, placing St. Charles County in the top tier for drinking-water safety. St. Charles County's drinking-water compliance score is 86.0 out of 100. As a routine precaution, requesting your utility's annual Consumer Confidence Report each July gives you a full list of detected contaminants and their treatment levels. With 36 active water-quality monitoring sites in St. Charles County, data coverage is strong. A pipeline streamflow snapshot from the Dardenne Creek gauge is also available on this page.

Regional Context

St. Charles County has better water quality than the average county in Missouri. Its water score is 37.2 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.

Past 5 years

Water Quality Monitoring

Monitoring Sites

36

Active in the past 5 years

Measurements Recorded

4.1K

4,057 total readings

Most Measured

  • Physical
  • Nutrient
  • Biological, Algae, Phytoplankton

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

3.16cfs

May 14, 7:00 PM UTC

vs Long-Term Average

3%

Well below typical

Primary Streamgage

Dardenne Creek at Old Town St. Peters, MO

USGS site
05514860
Drainage area
102 sq mi
Long-term mean
118 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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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 St. Charles County:B — Good

Minor violations; waterways mostly healthy.

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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St. Charles County has good water quality

Learn about water restrictions and conservation in your area.

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Frequently Asked Questions

What is the water quality in St. Charles County, Missouri?
St. Charles County, Missouri has a drinking-water quality grade of A with a score of 86.0/100, based on EPA SDWIS compliance data. The county has 0 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 St. Charles County?
St. Charles County has 0 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). Zero violations is an excellent record indicating consistent compliance with federal drinking water standards.
How much water-quality monitoring happens in St. Charles County?
EPA's Water Quality Portal records 4,057 measurements from 36 monitoring sites in St. Charles County over the past five years. The most frequently measured characteristic groups are Physical, Nutrient, Biological, Algae, Phytoplankton. 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 St. Charles County right now?
St. Charles County's primary USGS streamgage on the Dardenne Creek has a pipeline snapshot of 3.16 cubic feet per second — 3% of the long-term mean of 118.34 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 St. Charles County water compare to the Missouri average?
St. Charles County's SDWIS water quality score of 86.0/100 is higher than the Missouri state average of 48.8. The average water quality grade across Missouri is D, based on data from 115 counties with available SDWIS data.
Is tap water safe to drink in St. Charles County?
Based on EPA SDWIS data, St. Charles County has a water quality grade of A (86.0/100). 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 St. Charles County have clean drinking water?
St. Charles County has 0 health-based drinking water violations according to EPA records. With a water quality score of 86.0/100 and grade A, the county's drinking water meets EPA standards with no recorded health violations. 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 St. Charles County rank for water quality in Missouri?
St. Charles County ranks #29 out of 115 counties in Missouri by SDWIS water quality score (1 = best). With a score of 86.0/100, 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

Atchison County

Missouri

A

86.0

Water score

Barton County

Missouri

A

86.0

Water score

Bollinger County

Missouri

A

86.0

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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