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County water report

Marion County Water Report

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

Water grade

A

Water score

86.0

State rank

#11

of 102

Health violations

0

EPA SDWIS, 5-year lookback

Watershed impaired

29.4%

218 water bodies assessed

Monitoring sites

35

5,714 recent measurements

Live streamflow

11%

EAST FORK KASKASKIA RIVER NEAR SANDOVAL, IL

Water at a glance

Key Water Indicators for Marion County

EPA SDWIS

Safety Grade

A

Score: 86.0 / 100

EPA SDWIS

Active Violations

0

5-year health-based lookback

EPA ATTAINS

Watershed Health

29% impaired

218 bodies assessed

USGS NWIS

Streamflow Snapshot

11% of mean

EAST FORK KASKASKIA RIVER NEAR SANDOVAL, IL

EPA WQP

Monitoring Sites

35

5,714 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 Marion County’s Water

Drinking Water Quality Overview

EPA SDWIS

Marion 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 large county.

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 29.4% of assessed waterways carry an impairment designation (64 of 218 water bodies) across Marion County's watersheds. The leading impairment causes are phosphorus, total and dissolved oxygen. Impairment does not mean tap water is unsafe — it measures ambient waterway conditions upstream of treatment, not finished drinking water.

River & Streamflow Status

USGS NWIS

USGS NWIS gauge data (as of 2026-05-14T13:00:00.000-06:00) puts EAST FORK KASKASKIA RIVER at 12.9 cfs — well below its long-term average at 11% 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. Marion County has moderate coverage with 35 active monitoring sites with 5,714 recent measurements on record. Predominant monitoring categories include physical and inorganics, minor, metals. 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 Marion County

Water Verdict

Marion County 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.

Violation Context

Marion County has recorded zero health-based violations, indicating no recent health-based violations in the reporting period. The violation rate is zero per 100,000 people served, which is the best possible outcome.

Consumer Guidance

Marion County has zero recorded health-based violations in the EPA compliance record. Marion County's drinking-water compliance score is 86.0 out of 100. Elevated phosphorus in watershed assessments indicates agricultural runoff reaching local waterways — a concern for surface ecosystems, but one that municipal treatment plants are designed to filter out. Annual Consumer Confidence Reports confirm treatment effectiveness county by county. With 35 active water-quality monitoring sites in Marion County, data coverage is strong. A pipeline streamflow snapshot from the EAST FORK KASKASKIA RIVER gauge is also available on this page.

Regional Context

Marion County has better water quality than the average county in Illinois. Its water score is 38.2 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.

Contaminants & Resources

Key issues flagged in Marion County's water environment

Watershed Impairment Causes (EPA ATTAINS)

  • 1

    Phosphorus (excess nutrients)

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

  • 2

    Low dissolved oxygen

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

  • 3

    Mercury

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

Source: EPA ATTAINS · Reporting cycle 2022

Official EPA Resources for Marion County

EPA How's My Waterway

Interactive watershed health data for Marion County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Marion County

Consumer Confidence Reports (IL)

Annual water quality reports from utilities in Illinois

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

29.4%

64 of 218 assessed

Some impairment

Top Impairment Causes

  • 1

    PHOSPHORUS, TOTAL

  • 2

    DISSOLVED OXYGEN

  • 3

    MERCURY

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

35

Active in the past 5 years

Measurements Recorded

5.7K

5,714 total readings

Most Measured

  • Physical
  • Inorganics, Minor, Metals
  • 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

12.9cfs

May 14, 7:00 PM UTC

vs Long-Term Average

11%

Well below typical

Primary Streamgage

EAST FORK KASKASKIA RIVER NEAR SANDOVAL, IL

USGS site
05592900
Drainage area
113 sq mi
Long-term mean
117 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 Marion 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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Marion County has good water quality

Learn about water restrictions and conservation in your area.

Water Restrictions →

Frequently Asked Questions

What is the water quality in Marion County, Illinois?
Marion County, Illinois 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 Marion County?
Marion 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 healthy are the watersheds in Marion County?
EPA ATTAINS assessments under Clean Water Act §303(d) indicate 29.4% of Marion County's 218 assessed water bodies are classified as impaired (64 impaired). The top reported causes are PHOSPHORUS, TOTAL, DISSOLVED OXYGEN, MERCURY. 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 Marion County?
EPA's Water Quality Portal records 5,714 measurements from 35 monitoring sites in Marion County over the past five years. The most frequently measured characteristic groups are Physical, Inorganics, Minor, Metals, 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 Marion County right now?
Marion County's primary USGS streamgage on the EAST FORK KASKASKIA RIVER has a pipeline snapshot of 12.9 cubic feet per second — 11% of the long-term mean of 117.44 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 Marion County water compare to the Illinois average?
Marion County's SDWIS water quality score of 86.0/100 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 Marion County?
Based on EPA SDWIS data, Marion 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 Marion County have clean drinking water?
Marion 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 Marion County rank for water quality in Illinois?
Marion County ranks #11 out of 102 counties in Illinois 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

Alexander County

Illinois

A

86.0

Water score

Boone County

Illinois

A

86.0

Water score

Brown County

Illinois

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.

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.

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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