County water report

Hamilton County Water Report

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

Water grade

Water score

71.8

State rank

#14

of 88

Health violations

EPA SDWIS, 5-year lookback

Watershed impaired

0.0%

8 water bodies assessed

Monitoring sites

5,135 recent measurements

Live streamflow

22%

Mill Creek at Carthage OH

Water at a glance

Key Water Indicators for Hamilton County

EPA SDWIS

Safety Grade

Score: 71.8 / 100

EPA SDWIS

Active Violations

5-year health-based lookback

EPA ATTAINS

Watershed Health

0% impaired

8 bodies assessed

USGS NWIS

Streamflow Snapshot

22% of mean

Mill Creek at Carthage OH

EPA WQP

Monitoring Sites

5,135 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.

71.8/100

Health violations

Health-based violations

Violations per 100K served

0.2

Population-normalized SDWIS rate

Data center water stress

Hamilton County has 2 facilities in the DCWSI dataset.

ByCounty's DCWSI ranks this county #117 nationally by combining its water score with mapped data center density.

DCWSI

61.1

0-100 index

Facility count

45.0 density percentile

Discharge estimate

Not reported

EPA CWA fields where available

Water vs median

+21.8

Compared with US county median

Named operators

CyrusOne

Mapped facilities

CyrusOne CIN2
Cincinnati · CyrusOne
OSM
OpenStreetMap data center 36897140
Facility details limited
OSM

See the Hamilton County data-center report Review methodology

Data Center Water Budget Calculator

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

Facility size: 100 MW

1 MW1,000 MW

Cooling type

Utilization: 70%

40%100%

799K gallons/dayLow Impact

Your facility would use 3.1% of this county's existing industrial water baseline — well within sustainable range.

3.1% of county industrial baseline24.86 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 Hamilton County’s Water

Drinking Water Quality Overview

EPA SDWIS

Hamilton County earns an A grade for drinking water quality, scoring 71.8 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). None of the assessed waterways are listed as impaired (0 of 8 water bodies) across Hamilton 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 2026-05-14T15:00:00.000-04:00) puts Mill Creek at 39.4 cfs — well below its long-term average at 22% 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. Hamilton County has moderate coverage with 26 active monitoring sites with 5,135 recent measurements on record. Predominant monitoring categories include physical and nutrient. 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 Hamilton County

Water Verdict

Hamilton County, Ohio receives a good water quality assessment with a grade of A and a score of 71.8 out of 100. While the water supply is generally safe, occasional monitoring gaps or minor contaminant detections may occur. Separately, EPA ATTAINS assessments track 8 water bodies in the county's watershed, none of which are currently listed as impaired under the Clean Water Act. At the most recent USGS reading, local streamflow was below its historical mean at 21.9% — worth watching in drier seasons.

Violation Context

EPA SDWIS records for Hamilton County, Ohio show 2 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 0.2 violations per 100,000 people served, this rate is relatively low compared to many U.S. counties. For independent context, 5,135 water-quality monitoring results have been recorded across the county in the EPA Water Quality Portal over the past five years.

Consumer Guidance

Tap water in Hamilton County earns a Grade A overall with a small number of isolated health violations in the recent record. Hamilton County's drinking-water compliance score is 71.8 out of 100. The violation rate for Hamilton County is 0.2 per 100,000 people served. These violations were likely resolved quickly; Grade A reflects a strong multi-year compliance trend. Reviewing the most recent Consumer Confidence Report will show exactly which systems were affected and what corrective action was taken. With 26 active water-quality monitoring sites in Hamilton County, data coverage is strong. A pipeline streamflow snapshot from the Mill Creek gauge is also available on this page.

Regional Context

Hamilton County has better water quality than the average county in Ohio. Its water score is 15.6 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 Hamilton County's water environment

Official EPA Resources for Hamilton County

EPA How's My Waterway

Interactive watershed health data for Hamilton County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Hamilton 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 8 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

5.1K

5,135 total readings

Most Measured

Physical
Nutrient
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).

Live USGS Streamgage

River & Stream Conditions

Current Discharge

39.4cfs

May 14, 7:00 PM UTC

vs Long-Term Average

22%

Well below typical

Primary Streamgage

Mill Creek at Carthage OH

USGS site: 03259000
Drainage area: 115 sq mi
Long-term mean: 180 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 Hamilton 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 Hamilton County, Ohio?

Hamilton County, Ohio has a drinking-water quality grade of A with a score of 71.8/100, 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 Hamilton County?

Hamilton 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 Hamilton County?

EPA ATTAINS assessments under Clean Water Act §303(d) indicate 0.0% of Hamilton County's 8 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 Hamilton County?

EPA's Water Quality Portal records 5,135 measurements from 26 monitoring sites in Hamilton County over the past five years. The most frequently measured characteristic groups are Physical, Nutrient, 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.

What's happening with rivers in Hamilton County right now?

Hamilton County's primary USGS streamgage on the Mill Creek has a pipeline snapshot of 39.4 cubic feet per second — 22% of the long-term mean of 179.58 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 Hamilton County water compare to the Ohio average?

Hamilton County's SDWIS water quality score of 71.8/100 is higher 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 Hamilton County?

Based on EPA SDWIS data, Hamilton County has a water quality grade of A (71.8/100). 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 Hamilton County have clean drinking water?

Hamilton County has 2 health-based drinking water violations according to EPA records. With a water quality score of 71.8/100 and grade A, 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 Hamilton County rank for water quality in Ohio?

Hamilton County ranks #14 out of 88 counties in Ohio by SDWIS water quality score (1 = best). With a score of 71.8/100, 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

Mahoning County

Ohio

71.1

Water score

Greene County

Ohio

70.8

Water score

Lake County

Ohio

70.1

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 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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