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EPA SDWIS

Baltimore County Water Quality

Baltimore County, Maryland

Water Grade

F

Water Score

26.7

Violations

2

State Rank

#23

of 24 (1 = best)

EPA SDWIS Compliance

Drinking Water Quality

Water Quality Grade

F

Based on EPA compliance history and violation data

Water Score

26.7/100

Higher = better quality

Health Violations

2

Health-based violations

Violation Rate

81.2%

Systems with violations

Water Advisory: Baltimore County

Water Verdict

Baltimore County receives a poor water quality assessment with a grade of F and a score of 26.7 out of 100. The water supply has documented quality issues. Residents are strongly encouraged to use filtered or bottled water for drinking and to stay informed about utility improvement plans.

Violation Context

Baltimore County has recorded 2 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 81.2 violations per 1,000 residents, this rate is high and signals significant water quality management issues.

Consumer Guidance

Residents of Baltimore 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 2 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

Baltimore County has poorer water quality than the average county in Maryland. Its water score is 23.8 points lower than the state average, suggesting more challenges with contamination control or infrastructure than neighboring counties.

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

40.7%

87 of 214 assessed

Moderate concern

Top Impairment Causes

  • 1

    TEMPERATURE

  • 2

    PCBS IN FISH TISSUE

  • 3

    PHOSPHORUS, TOTAL

Source: EPA ATTAINS · Reporting cycle 2022

Impairment is determined under the Clean Water Act §303(d): a water body is impaired when it fails to meet state-defined quality standards for designated uses (drinking, recreation, aquatic life). Assessment coverage varies by state — counties without assessed water bodies are not shown.

Past 5 years

Water Quality Monitoring

Monitoring Sites

72

Active in the past 5 years

Measurements Recorded

48K

48,208 total readings

Most Measured

  • Physical
  • Nutrient
  • Microbiological

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

97.0cfs

May 14, 6:30 PM UTC

vs Long-Term Average

36%

Well below typical

Primary Streamgage

PATAPSCO RIVER NEAR CATONSVILLE, MD

USGS site
01589025
Drainage area
301 sq mi
Long-term mean
267 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 Baltimore County, Maryland?
Baltimore County, Maryland has a drinking-water quality grade of F with a score of 26.7/100, based on EPA SDWIS compliance data. The county has 2 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 Baltimore County?
Baltimore County has 2 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 healthy are the watersheds in Baltimore County?
EPA ATTAINS assessments under Clean Water Act §303(d) indicate 40.7% of Baltimore County's 214 assessed water bodies are classified as impaired (87 impaired). The top reported causes are TEMPERATURE, PCBS IN FISH TISSUE, PHOSPHORUS, TOTAL. Impairment means the water body fails to meet state quality standards for at least one designated use — drinking water source, recreation, aquatic life, or fish consumption. Note: watershed impairment doesn't always translate to tap-water issues; treatment plants can remove most regulated contaminants.
How much water-quality monitoring happens in Baltimore County?
EPA's Water Quality Portal records 48,208 measurements from 72 monitoring sites in Baltimore County over the past five years. The most frequently measured characteristic groups are Physical, Nutrient, Microbiological. 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 Baltimore County right now?
Baltimore County's primary USGS streamgage on the PATAPSCO RIVER is currently reading 97 cubic feet per second — 36% of the long-term mean of 267.3 cfs. This is well below typical — often a signal of drought stress on source water. For genuine real-time data, visit waterdata.usgs.gov.
How does Baltimore County water compare to the Maryland average?
Baltimore County's SDWIS water quality score of 26.7/100 is lower than the Maryland state average of 50.5. The average water quality grade across Maryland is D, based on data from 24 counties with available SDWIS data.
Is tap water safe to drink in Baltimore County?
Based on EPA SDWIS data, Baltimore County has a water quality grade of F (26.7/100). This indicates below-average compliance with significant violations. Residents may want to consider home water filtration or independent testing. 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 Baltimore County have clean drinking water?
Baltimore County has 2 health-based drinking water violations according to EPA records. With a water quality score of 26.7/100 and grade F, 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 Baltimore County rank for water quality in Maryland?
Baltimore County ranks #23 out of 24 counties in Maryland by SDWIS water quality score (1 = best). With a score of 26.7/100, it falls in the bottom 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

Caroline County

Maryland

F

27.7

Water score

Cecil County

Maryland

F

25.2

Water score

Talbot County

Maryland

F

32.1

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.

Watershed health and impaired-waterway data from the EPA ATTAINS Clean Water Act §303(d) assessments — state-reported, EPA-finalized.

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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