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County water report

Warren County Water Report

Drinking-water compliance, watershed health, monitoring records, and river conditions for Warren County, Illinois.

Water grade

D

Water score

50.1

State rank

#47

of 102

Health violations

2

EPA SDWIS, 5-year lookback

Watershed impaired

18.8%

271 water bodies assessed

Monitoring sites

1

7 recent measurements

Live streamflow

No gauge

CEDAR CREEK AT LITTLE YORK, IL

Water at a glance

Key Water Indicators for Warren County

EPA SDWIS

Safety Grade

D

Score: 50.1 / 100

EPA SDWIS

Active Violations

2

5-year health-based lookback

EPA ATTAINS

Watershed Health

19% impaired

271 bodies assessed

USGS NWIS

Streamflow Snapshot

No gauge

CEDAR CREEK AT LITTLE YORK, IL

EPA WQP

Monitoring Sites

1

7 recent readings

Source: EPA SDWIS · Safe Drinking Water Information System

Drinking Water Compliance

Compliance grade

D

Based on EPA SDWIS compliance history.

Water score

Higher scores indicate cleaner recent compliance records.

50.1/100

Health violations

2

Health-based violations

Violations per 100K served

16.5

Population-normalized SDWIS rate

Editorial analysis

Understanding Warren County’s Water

Drinking Water Quality Overview

EPA SDWIS

Warren County's drinking water received a D grade, scoring 50.1 out of 100. Over the past five years, EPA SDWIS records 2 health-based violations — a small cluster that warrants attention.

Watershed Conditions

EPA ATTAINS

Under the Clean Water Act §303(d), EPA ATTAINS tracks whether waterways meet quality standards for drinking, recreation, and aquatic life (reporting cycle: 2022). A notable 18.8% of assessed waterways carry an impairment designation (51 of 271 water bodies) across Warren County's watersheds. The leading impairment causes are mercury and polychlorinated biphenyls (pcbs). Impairment does not mean tap water is unsafe — it measures ambient waterway conditions upstream of treatment, not finished drinking water.

Monitoring Network

EPA WQP

EPA's Water Quality Portal (WQP) aggregates monitoring data from federal, state, and tribal agencies. Warren County has limited coverage with 1 active monitoring site with 7 recent measurements on record. Predominant monitoring categories include organics, pesticide and organics, other. 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 Warren County

Water Verdict

Warren County receives a below-average water quality assessment with a grade of D and a score of 50.1 out of 100. Residents should review their utility's Consumer Confidence Report and may want to consider additional water filtration for drinking.

Violation Context

Warren County has recorded 2 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 16.5 violations per 100,000 people served, this rate is high and signals significant water quality management issues.

Consumer Guidance

Warren County's drinking-water compliance is below average with a Grade D, indicating repeated or unresolved violations in the recent record. Warren County's drinking-water compliance score is 50.1 out of 100. The violation rate for Warren County is 16.5 per 100,000 people served. Residents are encouraged to use an NSF 53 or NSF 58-certified filter for drinking and cooking water until the underlying violations are resolved. Running tap water for 30 seconds before use and avoiding older lead-pipe connections can also reduce exposure risk. The current Consumer Confidence Report from your utility will specify the contaminants of concern. Mercury is the leading impairment cause in Warren County's watershed. There is 1 active water-quality monitoring site in Warren County. A pipeline streamflow snapshot from the CEDAR CREEK gauge is also available on this page.

Regional Context

Warren County has water quality close to the average county in Illinois. Its water score is within 2.3 points of the state average, meaning its overall water system performance is broadly representative of Illinois as a whole.

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 Warren County's water environment

Watershed Impairment Causes (EPA ATTAINS)

  • 1

    Mercury

    Impairment cause per EPA Clean Water Act §303(d) assessment

  • 2

    Polychlorinated Biphenyls (Pcbs)

    Impairment cause per EPA Clean Water Act §303(d) assessment

  • 3

    Phosphorus (excess nutrients)

    Impairment cause per EPA Clean Water Act §303(d) assessment

Source: EPA ATTAINS · Reporting cycle 2022

Official EPA Resources for Warren County

EPA How's My Waterway

Interactive watershed health data for Warren County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Warren County

Consumer Confidence Reports (IL)

Annual water quality reports from utilities in Illinois

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

18.8%

51 of 271 assessed

Some impairment

Top Impairment Causes

  • 1

    MERCURY

  • 2

    POLYCHLORINATED BIPHENYLS (PCBS)

  • 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

1

Active in the past 5 years

Measurements Recorded

7

7 total readings

Most Measured

  • Organics, Pesticide
  • Organics, Other

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).

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Water Cost Estimate

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Annual Total

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Monthly

$47

Water Bill

$558/yr

Filter Cost

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Safety Grade for Warren 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 Warren County, Illinois?
Warren County, Illinois has a drinking-water quality grade of D with a score of 50.1/100, 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 streamflow snapshots are reported separately on this page.
Are there any water violations in Warren County?
Warren 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 Warren County?
EPA ATTAINS assessments under Clean Water Act §303(d) indicate 18.8% of Warren County's 271 assessed water bodies are classified as impaired (51 impaired). The top reported causes are MERCURY, POLYCHLORINATED BIPHENYLS (PCBS), 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 Warren County?
EPA's Water Quality Portal records 7 measurements from 1 monitoring sites in Warren County over the past five years. The most frequently measured characteristic groups are Organics, Pesticide, Organics, Other. 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.
How does Warren County water compare to the Illinois average?
Warren County's SDWIS water quality score of 50.1/100 is higher than the Illinois state average of 47.8. The average water quality grade across Illinois is D, based on data from 102 counties with available SDWIS data.
Is tap water safe to drink in Warren County?
Based on EPA SDWIS data, Warren County has a water quality grade of D (50.1/100). 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 Warren County have clean drinking water?
Warren County has 2 health-based drinking water violations according to EPA records. With a water quality score of 50.1/100 and grade D, 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 Warren County rank for water quality in Illinois?
Warren County ranks #47 out of 102 counties in Illinois by SDWIS water quality score (1 = best). With a score of 50.1/100, 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

Carroll County

Illinois

D

48.9

Water score

Ford County

Illinois

D

48.6

Water score

Whiteside County

Illinois

C

52.3

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.

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

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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