Jefferson County Water Quality
Jefferson County, Missouri
Water Grade
D
Water Score
50.5
Violations
28
State Rank
#44
of 115 (1 = best)
EPA SDWIS Compliance
Drinking Water Quality
Water Quality Grade
D
Based on EPA compliance history and violation data
Water Score
50.5/100
Higher = better quality
Health Violations
28
Health-based violations
Violation Rate
15.5%
Systems with violations
Water Advisory: Jefferson County
Water Verdict
Jefferson County receives a below-average water quality assessment with a grade of D and a score of 50.5 out of 100. Residents should review their utility's Consumer Confidence Report and may want to consider additional water filtration for drinking.
Violation Context
Jefferson County has recorded 28 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 15.5 violations per 1,000 residents, this rate is high and signals significant water quality management issues.
Consumer Guidance
Residents of Jefferson County are advised to use filtered or bottled water for drinking and cooking until water quality improves. A reverse-osmosis or activated-carbon filter certified to remove the contaminants listed in the utility's Consumer Confidence Report is recommended. With 28 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
Jefferson County has water quality close to the average county in Missouri. Its water score is within 1.7 points of the state average, meaning its overall water system performance is broadly representative of Missouri as a whole.
Past 5 years
Water Quality Monitoring
Monitoring Sites
16
Active in the past 5 years
Measurements Recorded
4.8K
4,825 total readings
Most Measured
- Nutrient
- Physical
- 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
601cfs
May 14, 6:45 PM UTC
vs Long-Term Average
68%
Below typicalPrimary Streamgage
Big River at Byrnesville, MO
- USGS site
- 07018500
- Drainage area
- 917 sq mi
- Long-term mean
- 887 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 Jefferson County, Missouri?
Are there any water violations in Jefferson County?
How much water-quality monitoring happens in Jefferson County?
What's happening with rivers in Jefferson County right now?
How does Jefferson County water compare to the Missouri average?
Is tap water safe to drink in Jefferson County?
Why does Jefferson County have so many water violations?
How does Jefferson County rank for water quality in Missouri?
Counties with Similar Water Quality
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.