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County water report

Marathon County Water Report

Drinking-water compliance, watershed health, monitoring records, and river conditions for Marathon County, Wisconsin.

Water grade

D

Water score

50.7

State rank

#19

of 71

Health violations

14

EPA SDWIS, 5-year lookback

Watershed impaired

4.3%

847 water bodies assessed

Monitoring sites

113

58,928 recent measurements

Live streamflow

66%

WISCONSIN RIVER AT ROTHSCHILD, WI

Water at a glance

Key Water Indicators for Marathon County

EPA SDWIS

Safety Grade

D

Score: 50.7 / 100

EPA SDWIS

Active Violations

14

5-year health-based lookback

EPA ATTAINS

Watershed Health

4% impaired

847 bodies assessed

USGS NWIS

Streamflow Snapshot

66% of mean

WISCONSIN RIVER AT ROTHSCHILD, WI

EPA WQP

Monitoring Sites

113

58,928 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.

50.7/100

Health violations

14

Health-based violations

Violations per 100K served

15.1

Population-normalized SDWIS rate

Editorial analysis

Understanding Marathon County’s Water

Drinking Water Quality Overview

EPA SDWIS

Marathon County's drinking water received a D grade, scoring 50.7 out of 100. Over the past five years, EPA SDWIS records 14 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). A small share — 4.3% — of assessed waterways are impaired (36 of 847 water bodies) across Marathon County's watersheds. The leading impairment causes are phosphorus, total and cause unknown. 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 2026-05-14T13:00:00.000-05:00) puts WISCONSIN RIVER at 2.5k cfs — running somewhat below its historical average at 66% 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. Marathon County has extensive coverage with 113 active monitoring sites with 58,928 recent measurements on record. Predominant monitoring categories include physical and organics, pesticide. 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 Marathon County

Water Verdict

Marathon County, Wisconsin receives a below-average water quality assessment with a grade of D and a score of 50.7 out of 100. Residents should review their utility's Consumer Confidence Report and may want to consider additional water filtration for drinking. Separately, EPA ATTAINS assessments cover 847 water bodies in the county's watershed, with 4.3% listed as impaired under the Clean Water Act — a source-water measure that is tracked independently of tap-water compliance. At the most recent USGS reading, local streamflow was below its historical mean at 66.4% — worth watching in drier seasons.

Violation Context

EPA SDWIS records for Marathon County, Wisconsin show 14 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 15.1 violations per 100,000 people served, this rate is high and signals significant water quality management issues. This compliance record sits alongside an unusually deep monitoring archive: 58,928 water-quality results have been logged across the county in the EPA Water Quality Portal over the past five years.

Consumer Guidance

Marathon County's drinking-water compliance is below average with a Grade D, indicating repeated or unresolved violations in the recent record. Marathon County's drinking-water compliance score is 50.7 out of 100. The violation rate for Marathon County is 15.1 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. Phosphorus, Total is the leading impairment cause in Marathon County's watershed. With 113 active water-quality monitoring sites in Marathon County, data coverage is strong. A pipeline streamflow snapshot from the WISCONSIN RIVER gauge is also available on this page.

Regional Context

Marathon County has better water quality than the average county in Wisconsin. Its water score is 11.2 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 Marathon County's water environment

Watershed Impairment Causes (EPA ATTAINS)

  • 1

    Phosphorus (excess nutrients)

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

  • 2

    Cause Unknown

    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 Marathon County

EPA How's My Waterway

Interactive watershed health data for Marathon County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Marathon County

Consumer Confidence Reports (WI)

Annual water quality reports from utilities in Wisconsin

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

4.3%

36 of 847 assessed

Mostly healthy

Top Impairment Causes

  • 1

    PHOSPHORUS, TOTAL

  • 2

    CAUSE UNKNOWN

  • 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

113

Active in the past 5 years

Measurements Recorded

59K

58,928 total readings

Most Measured

  • Physical
  • Organics, Pesticide
  • 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

2,480cfs

May 14, 6:00 PM UTC

vs Long-Term Average

66%

Below typical

Primary Streamgage

WISCONSIN RIVER AT ROTHSCHILD, WI

USGS site
05398000
Drainage area
4,020 sq mi
Long-term mean
3,732 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.

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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 Marathon 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 Marathon County, Wisconsin?
Marathon County, Wisconsin has a drinking-water quality grade of D with a score of 50.7/100, based on EPA SDWIS compliance data. The county has 14 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 Marathon County?
Marathon County has 14 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 Marathon County?
EPA ATTAINS assessments under Clean Water Act §303(d) indicate 4.3% of Marathon County's 847 assessed water bodies are classified as impaired (36 impaired). The top reported causes are PHOSPHORUS, TOTAL, CAUSE UNKNOWN, 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 Marathon County?
EPA's Water Quality Portal records 58,928 measurements from 113 monitoring sites in Marathon County over the past five years. The most frequently measured characteristic groups are Physical, Organics, Pesticide, 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 Marathon County right now?
Marathon County's primary USGS streamgage on the WISCONSIN RIVER has a pipeline snapshot of 2,480 cubic feet per second — 66% of the long-term mean of 3,732.4 cfs. Flow is within typical range for this gauge. For the latest gauge feed, visit waterdata.usgs.gov.
How does Marathon County water compare to the Wisconsin average?
Marathon County's SDWIS water quality score of 50.7/100 is higher than the Wisconsin state average of 39.5. The average water quality grade across Wisconsin is F, based on data from 71 counties with available SDWIS data.
Is tap water safe to drink in Marathon County?
Based on EPA SDWIS data, Marathon County has a water quality grade of D (50.7/100). 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 Marathon County have so many water violations?
Marathon County has 14 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 Marathon County rank for water quality in Wisconsin?
Marathon County ranks #19 out of 71 counties in Wisconsin by SDWIS water quality score (1 = best). With a score of 50.7/100, 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

Manitowoc County

Wisconsin

C

51.8

Water score

Kenosha County

Wisconsin

D

49.0

Water score

Dunn County

Wisconsin

D

48.2

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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