County water report

Clark County Water Report

Drinking-water compliance, watershed health, monitoring records, and river conditions for Clark County, Ohio.

Water grade

Water score

41.6

State rank

#70

of 88

Health violations

EPA SDWIS, 5-year lookback

Watershed impaired

0.0%

6 water bodies assessed

Monitoring sites

5,787 recent measurements

Live streamflow

60%

Mad River near Springfield OH

Water at a glance

Key Water Indicators for Clark County

EPA SDWIS

Safety Grade

Score: 41.6 / 100

EPA SDWIS

Active Violations

5-year health-based lookback

EPA ATTAINS

Watershed Health

0% impaired

6 bodies assessed

USGS NWIS

Streamflow Snapshot

60% of mean

Mad River near Springfield OH

EPA WQP

Monitoring Sites

5,787 recent readings

Source: EPA SDWIS · Safe Drinking Water Information System

Drinking Water Compliance

Compliance grade

Based on EPA SDWIS compliance history.

Water score

Higher scores indicate cleaner recent compliance records.

41.6/100

Health violations

Health-based violations

Violations per 100K served

29.2

Population-normalized SDWIS rate

Data center water stress

Clark County has 2 facilities in the DCWSI dataset.

ByCounty's DCWSI ranks this county #991 nationally by combining its water score with mapped data center density.

DCWSI

43.0

0-100 index

Facility count

45.0 density percentile

Discharge estimate

Not reported

EPA CWA fields where available

Water vs median

-8.4

Compared with US county median

Mapped facilities

CMH01 HOLDINGS LP
SPRINGFIELD
EPA ECHO
LexisNexus Springfield
Springfield
OSM

See the Clark County data-center report Review methodology

Data Center Water Budget Calculator

Estimate daily water use for a hypothetical facility in Clark County.

Facility size: 100 MW

1 MW1,000 MW

Cooling type

Utilization: 70%

40%100%

799K gallons/dayHigh Impact

Your facility would use 78.1% of this county's industrial water baseline. Verify water rights and long-term drought projections before committing.

78.1% of county industrial baseline0.22 Mgal/day remaining headroom

Based on USGS 2020 water-use data and EPA-standard cooling intensity constants. Not a substitute for site-specific water rights analysis.

Editorial analysis

Understanding Clark County’s Water

Drinking Water Quality Overview

EPA SDWIS

Clark County's drinking water received a D grade, scoring 41.6 out of 100. Over the past five years, EPA SDWIS records 27 health-based violations — a pattern that public water utilities are required to disclose and correct.

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). None of the assessed waterways are listed as impaired (0 of 6 water bodies) across Clark County's watersheds. 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 2026-05-14T14:15:00.000-04:00) puts Mad River at 347.0 cfs — running somewhat below its historical average at 60% of mean. 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. Clark County has extensive coverage with 62 active monitoring sites with 5,787 recent measurements on record. Predominant monitoring categories include physical 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 Clark County

Water Verdict

Clark County receives a below-average water quality assessment with a grade of D and a score of 41.6 out of 100. Residents should review their utility's Consumer Confidence Report and may want to consider additional water filtration for drinking.

Violation Context

Clark County has recorded 27 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 29.2 violations per 100,000 people served, this rate is high and signals significant water quality management issues.

Consumer Guidance

Clark County's drinking-water compliance is below average with a Grade D, indicating repeated or unresolved violations in the recent record. Clark County's drinking-water compliance score is 41.6 out of 100. The violation rate for Clark County is 29.2 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. With 62 active water-quality monitoring sites in Clark County, data coverage is strong. A pipeline streamflow snapshot from the Mad River gauge is also available on this page.

Regional Context

Clark County has poorer water quality than the average county in Ohio. Its water score is 14.6 points lower than the state average, suggesting more challenges with contamination control or infrastructure than 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 Clark County's water environment

Official EPA Resources for Clark County

EPA How's My Waterway

Interactive watershed health data for Clark County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Clark County

Consumer Confidence Reports (OH)

Annual water quality reports from utilities in Ohio

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

0.0%

0 of 6 assessed

Mostly healthy

Top Impairment Causes

No specific impairment causes reported for the assessed water bodies in this county.

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

Active in the past 5 years

Measurements Recorded

5.8K

5,787 total readings

Most Measured

Physical
Organics, Other
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

347cfs

May 14, 6:15 PM UTC

vs Long-Term Average

60%

Below typical

Primary Streamgage

Mad River near Springfield OH

USGS site: 03269500
Drainage area: 490 sq mi
Long-term mean: 577 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

Household size

3 people · ~225 gal/day

Filter type

Annual Total

$558

Monthly

$47

Water Bill

$558/yr

Filter Cost

$0/yr

Safety Grade for Clark 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.

Try the full calculator →

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Frequently Asked Questions

What is the water quality in Clark County, Ohio?

Clark County, Ohio has a drinking-water quality grade of D with a score of 41.6/100, based on EPA SDWIS compliance data. The county has 27 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 Clark County?

Clark County has 27 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 Clark County?

EPA ATTAINS assessments under Clean Water Act §303(d) indicate 0.0% of Clark County's 6 assessed water bodies are classified as impaired (0 impaired). 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 Clark County?

EPA's Water Quality Portal records 5,787 measurements from 62 monitoring sites in Clark County over the past five years. The most frequently measured characteristic groups are Physical, Organics, Other, 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 Clark County right now?

Clark County's primary USGS streamgage on the Mad River has a pipeline snapshot of 347 cubic feet per second — 60% of the long-term mean of 576.87 cfs. Flow is within typical range for this gauge. For the latest gauge feed, visit waterdata.usgs.gov.

How does Clark County water compare to the Ohio average?

Clark County's SDWIS water quality score of 41.6/100 is lower than the Ohio state average of 56.2. The average water quality grade across Ohio is D, based on data from 88 counties with available SDWIS data.

Is tap water safe to drink in Clark County?

Based on EPA SDWIS data, Clark County has a water quality grade of D (41.6/100). 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).

Why does Clark County have so many water violations?

Clark County has 27 health-based drinking water violations on record from the EPA SDWIS database. A higher violation count can result from aging infrastructure, underfunded water utilities, agricultural runoff contamination, or industrial pollution. Counties with more water systems may also see more violations simply due to scale. Residents concerned about water quality should consider independent water testing and home filtration systems.

How does Clark County rank for water quality in Ohio?

Clark County ranks #70 out of 88 counties in Ohio by SDWIS water quality score (1 = best). With a score of 41.6/100, 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

Carroll County

Ohio

42.0

Water score

Richland County

Ohio

42.4

Water score

Guernsey County

Ohio

42.6

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 May 14, 2026Reviewed by Evan Brooks, Data Editor

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