County water report

Johnson County Water Report

Drinking-water compliance, watershed health, monitoring records, and river conditions for Johnson County, Iowa.

Water grade

Water score

37.9

State rank

#83

of 99

Health violations

EPA SDWIS, 5-year lookback

Watershed impaired

Not reported

EPA ATTAINS coverage varies by state

Monitoring sites

6,263 recent measurements

Live streamflow

85%

Iowa River at Iowa City, IA

Water at a glance

Key Water Indicators for Johnson County

EPA SDWIS

Safety Grade

Score: 37.9 / 100

EPA SDWIS

Active Violations

5-year health-based lookback

EPA ATTAINS

Watershed Health

Not reported

Coverage varies by state

USGS NWIS

Streamflow Snapshot

85% of mean

Iowa River at Iowa City, IA

EPA WQP

Monitoring Sites

6,263 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.

37.9/100

Health violations

Health-based violations

Violations per 100K served

37.7

Population-normalized SDWIS rate

Data center water stress

Johnson County has 1 facility in the DCWSI dataset.

ByCounty's DCWSI ranks this county #1921 nationally by combining its water score with mapped data center density.

DCWSI

22.7

0-100 index

Facility count

0.0 density percentile

Discharge estimate

Not reported

EPA CWA fields where available

Water vs median

-12.1

Compared with US county median

Mapped facilities

ForceAmp.com
Facility details limited
OSM

See the Johnson County data-center report Review methodology

Data Center Water Budget Calculator

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

Facility size: 100 MW

1 MW1,000 MW

Cooling type

Utilization: 70%

40%100%

799K gallons/dayHigh Impact

Your facility would use 69.2% of this county's industrial water baseline. Verify water rights and long-term drought projections before committing.

69.2% of county industrial baseline0.36 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 Johnson County’s Water

Drinking Water Quality Overview

EPA SDWIS

Johnson County's water systems carry a failing grade, scoring 37.9 out of 100. Over the past five years, EPA SDWIS records 60 health-based violations — a pattern that public water utilities are required to disclose and correct.

River & Streamflow Status

USGS NWIS

USGS NWIS gauge data (as of 2026-05-14T14:00:00.000-05:00) puts Iowa River at 2.1k cfs — running somewhat below its historical average at 85% 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. Johnson County has moderate coverage with 15 active monitoring sites with 6,263 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 Johnson County

Water Verdict

Johnson County receives a poor water quality assessment with a grade of F and a score of 37.9 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

Johnson County has recorded 60 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 37.7 violations per 100,000 people served, this rate is high and signals significant water quality management issues.

Consumer Guidance

Johnson County has a Grade F compliance record with 60 health-based violations — among the highest levels in the country. Johnson County's drinking-water compliance score is 37.9 out of 100. The violation rate for Johnson County is 37.7 per 100,000 people served. Residents are strongly advised to use a certified NSF 58 reverse-osmosis filter or bottled water for all drinking and cooking until violations are corrected. Contacting the Iowa Department of Environmental Quality or Health can expedite utility compliance action. With 15 active water-quality monitoring sites in Johnson County, data coverage is strong. A pipeline streamflow snapshot from the Iowa River gauge is also available on this page.

Regional Context

Johnson County has poorer water quality than the average county in Iowa. Its water score is 33.8 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 Johnson County's water environment

Official EPA Resources for Johnson County

EPA How's My Waterway

Interactive watershed health data for Johnson County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Johnson County

Consumer Confidence Reports (IA)

Annual water quality reports from utilities in Iowa

Past 5 years

Water Quality Monitoring

Monitoring Sites

Active in the past 5 years

Measurements Recorded

6.3K

6,263 total readings

Most Measured

Physical
Organics, Other
Organics, Pesticide

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

2,120cfs

May 14, 7:00 PM UTC

vs Long-Term Average

85%

Below typical

Primary Streamgage

Iowa River at Iowa City, IA

USGS site: 05454500
Drainage area: 3,271 sq mi
Long-term mean: 2,508 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 Johnson County:F — Failing

High violation count or severe watershed conditions.

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 Johnson County, Iowa?

Johnson County, Iowa has a drinking-water quality grade of F with a score of 37.9/100, based on EPA SDWIS compliance data. The county has 60 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 Johnson County?

Johnson County has 60 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 much water-quality monitoring happens in Johnson County?

EPA's Water Quality Portal records 6,263 measurements from 15 monitoring sites in Johnson County over the past five years. The most frequently measured characteristic groups are Physical, Organics, Other, Organics, Pesticide. 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 Johnson County right now?

Johnson County's primary USGS streamgage on the Iowa River has a pipeline snapshot of 2,120 cubic feet per second — 85% of the long-term mean of 2,507.79 cfs. Flow is within typical range for this gauge. For the latest gauge feed, visit waterdata.usgs.gov.

How does Johnson County water compare to the Iowa average?

Johnson County's SDWIS water quality score of 37.9/100 is lower than the Iowa state average of 71.7. The average water quality grade across Iowa is C, based on data from 99 counties with available SDWIS data.

Is tap water safe to drink in Johnson County?

Based on EPA SDWIS data, Johnson County has a water quality grade of F (37.9/100). 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 Johnson County have so many water violations?

Johnson County has 60 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 Johnson County rank for water quality in Iowa?

Johnson County ranks #83 out of 99 counties in Iowa by SDWIS water quality score (1 = best). With a score of 37.9/100, 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

Pocahontas County

Iowa

37.5

Water score

Cedar County

Iowa

39.4

Water score

Hancock County

Iowa

36.4

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.

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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