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County water report

Fond du Lac County Water Report

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

Water grade

C

Water score

60.4

State rank

#12

of 71

Health violations

4

EPA SDWIS, 5-year lookback

Watershed impaired

13.4%

359 water bodies assessed

Monitoring sites

81

150,371 recent measurements

Live streamflow

248%

SOUTH BRANCH ROCK RIVER AT WAUPUN, WI

Water at a glance

Key Water Indicators for Fond du Lac County

EPA SDWIS

Safety Grade

C

Score: 60.4 / 100

EPA SDWIS

Active Violations

4

5-year health-based lookback

EPA ATTAINS

Watershed Health

13% impaired

359 bodies assessed

USGS NWIS

Streamflow Snapshot

248% of mean

SOUTH BRANCH ROCK RIVER AT WAUPUN, WI

EPA WQP

Monitoring Sites

81

150,371 recent readings

Source: EPA SDWIS · Safe Drinking Water Information System

Drinking Water Compliance

Compliance grade

C

Based on EPA SDWIS compliance history.

Water score

Higher scores indicate cleaner recent compliance records.

60.4/100

Health violations

4

Health-based violations

Violations per 100K served

6.2

Population-normalized SDWIS rate

Editorial analysis

Understanding Fond du Lac County’s Water

Drinking Water Quality Overview

EPA SDWIS

Fond du Lac County's drinking water earned a C grade, scoring 60.4 out of 100. Over the past five years, EPA SDWIS records 4 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 notable 13.4% of assessed waterways carry an impairment designation (48 of 359 water bodies) across Fond du Lac County's watersheds. The leading impairment causes are phosphorus, total and total suspended solids (tss). 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 2026-05-14T14:00:00.000-05:00) puts SOUTH BRANCH ROCK RIVER at 92.1 cfs — running significantly above its long-term average at 248% of mean flow. 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. Fond du Lac County has extensive coverage with 81 active monitoring sites with 150,371 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 Fond du Lac County

Water Verdict

Fond du Lac County receives a fair water quality assessment with a grade of C and a score of 60.4 out of 100. The water supply meets baseline federal standards, but there may be periods of elevated contaminant levels or infrastructure concerns worth monitoring.

Violation Context

Fond du Lac County has recorded 4 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 6.2 violations per 100,000 people served, this rate is moderate and suggests recurring water quality challenges.

Consumer Guidance

Tap water in Fond du Lac County meets baseline standards but the compliance record shows room for improvement, with a Grade C rating. Fond du Lac County's drinking-water compliance score is 60.4 out of 100. The violation rate for Fond du Lac County is 6.2 per 100,000 people served. Residents who are immunocompromised, pregnant, or have young children may benefit from using an NSF 53-certified filter. Contacting your local utility for the current Consumer Confidence Report will confirm which specific violations were recorded and whether they have been resolved. Phosphorus, Total is the leading impairment cause in Fond du Lac County's watershed. With 81 active water-quality monitoring sites in Fond du Lac County, data coverage is strong. A pipeline streamflow snapshot from the SOUTH BRANCH ROCK RIVER gauge is also available on this page.

Regional Context

Fond du Lac County has better water quality than the average county in Wisconsin. Its water score is 20.9 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 Fond du Lac County's water environment

Watershed Impairment Causes (EPA ATTAINS)

  • 1

    Phosphorus (excess nutrients)

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

  • 2

    Total Suspended Solids (Tss)

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

  • 3

    Cause Unknown

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

Source: EPA ATTAINS · Reporting cycle 2022

Official EPA Resources for Fond du Lac County

EPA How's My Waterway

Interactive watershed health data for Fond du Lac County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Fond du Lac County

Consumer Confidence Reports (WI)

Annual water quality reports from utilities in Wisconsin

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

13.4%

48 of 359 assessed

Some impairment

Top Impairment Causes

  • 1

    PHOSPHORUS, TOTAL

  • 2

    TOTAL SUSPENDED SOLIDS (TSS)

  • 3

    CAUSE UNKNOWN

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

81

Active in the past 5 years

Measurements Recorded

150K

150,371 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

92.1cfs

May 14, 7:00 PM UTC

vs Long-Term Average

248%

Well above typical

Primary Streamgage

SOUTH BRANCH ROCK RIVER AT WAUPUN, WI

USGS site
05423500
Drainage area
63.6 sq mi
Long-term mean
37.1 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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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 Fond du Lac 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 Fond du Lac County, Wisconsin?
Fond du Lac County, Wisconsin has a drinking-water quality grade of C with a score of 60.4/100, based on EPA SDWIS compliance data. The county has 4 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 Fond du Lac County?
Fond du Lac County has 4 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 Fond du Lac County?
EPA ATTAINS assessments under Clean Water Act §303(d) indicate 13.4% of Fond du Lac County's 359 assessed water bodies are classified as impaired (48 impaired). The top reported causes are PHOSPHORUS, TOTAL, TOTAL SUSPENDED SOLIDS (TSS), CAUSE UNKNOWN. 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 Fond du Lac County?
EPA's Water Quality Portal records 150,371 measurements from 81 monitoring sites in Fond du Lac 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 Fond du Lac County right now?
Fond du Lac County's primary USGS streamgage on the SOUTH BRANCH ROCK RIVER has a pipeline snapshot of 92.1 cubic feet per second — 248% of the long-term mean of 37.1 cfs. This is well above typical — often a signal of recent precipitation or storm runoff. For the latest gauge feed, visit waterdata.usgs.gov.
How does Fond du Lac County water compare to the Wisconsin average?
Fond du Lac County's SDWIS water quality score of 60.4/100 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 Fond du Lac County?
Based on EPA SDWIS data, Fond du Lac County has a water quality grade of C (60.4/100). This indicates moderate compliance. Some violations have been recorded but overall standards are maintained. 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 Fond du Lac County have clean drinking water?
Fond du Lac County has 4 health-based drinking water violations according to EPA records. With a water quality score of 60.4/100 and grade C, 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 Fond du Lac County rank for water quality in Wisconsin?
Fond du Lac County ranks #12 out of 71 counties in Wisconsin by SDWIS water quality score (1 = best). With a score of 60.4/100, 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

Sheboygan County

Wisconsin

C

61.2

Water score

La Crosse County

Wisconsin

C

61.5

Water score

Brown County

Wisconsin

B

62.3

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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