waterbycounty
EPA SDWIS

Washtenaw County Water Quality

Washtenaw County, Michigan

Water Grade

C

Water Score

61.4

Violations

21

State Rank

#40

of 83 (1 = best)

EPA SDWIS Compliance

Drinking Water Quality

Water Quality Grade

C

Based on EPA compliance history and violation data

Water Score

61.4/100

Higher = better quality

Health Violations

21

Health-based violations

Violation Rate

5.5%

Systems with violations

Water Advisory: Washtenaw County

Water Verdict

Washtenaw County receives a fair water quality assessment with a grade of C and a score of 61.4 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

Washtenaw County has recorded 21 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 5.5 violations per 1,000 residents, this rate is moderate and suggests recurring water quality challenges.

Consumer Guidance

Tap water in Washtenaw County meets baseline standards, but residents who are immunocompromised or have young children may want to use an NSF-certified water filter as a precaution. With 21 recorded health violations, staying informed about utility communications and boil-water notices is especially important. For long-term peace of mind, request your utility's latest Consumer Confidence Report and consider independent water testing if you have specific health concerns.

Regional Context

Washtenaw County has water quality close to the average county in Michigan. Its water score is within 2.9 points of the state average, meaning its overall water system performance is broadly representative of Michigan as a whole.

Past 5 years

Water Quality Monitoring

Monitoring Sites

42

Active in the past 5 years

Measurements Recorded

8.2K

8,216 total readings

Most Measured

  • Physical
  • Not Assigned
  • Microbiological

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

382cfs

May 14, 7:00 PM UTC

vs Long-Term Average

80%

Below typical

Primary Streamgage

HURON RIVER AT ANN ARBOR, MI

USGS site
04174500
Drainage area
729 sq mi
Long-term mean
475 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; "% of typical" compares the latest reading against that average.

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Frequently Asked Questions

What is the water quality in Washtenaw County, Michigan?
Washtenaw County, Michigan has a drinking-water quality grade of C with a score of 61.4/100, based on EPA SDWIS compliance data. The county has 21 health-based drinking water violations over the past 5 years. Watershed health, monitoring records, and live streamflow are reported separately on this page.
Are there any water violations in Washtenaw County?
Washtenaw County has 21 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 Washtenaw County?
EPA's Water Quality Portal records 8,216 measurements from 42 monitoring sites in Washtenaw County over the past five years. The most frequently measured characteristic groups are Physical, Not Assigned, Microbiological. 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 Washtenaw County right now?
Washtenaw County's primary USGS streamgage on the HURON RIVER is currently reading 382 cubic feet per second — 80% of the long-term mean of 474.93 cfs. Flow is within typical range for this gauge. For genuine real-time data, visit waterdata.usgs.gov.
How does Washtenaw County water compare to the Michigan average?
Washtenaw County's SDWIS water quality score of 61.4/100 is higher than the Michigan state average of 58.5. The average water quality grade across Michigan is D, based on data from 83 counties with available SDWIS data.
Is tap water safe to drink in Washtenaw County?
Based on EPA SDWIS data, Washtenaw County has a water quality grade of C (61.4/100). 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).
Why does Washtenaw County have so many water violations?
Washtenaw County has 21 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 Washtenaw County rank for water quality in Michigan?
Washtenaw County ranks #40 out of 83 counties in Michigan by SDWIS water quality score (1 = best). With a score of 61.4/100, it falls in the middle 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

Ingham County

Michigan

C

61.7

Water score

Huron County

Michigan

C

60.4

Water score

Oakland County

Michigan

B

62.6

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.

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 Logan Johnson, Founder & Data EditorUpdated Reviewed by Logan Johnson, Founder & Data Editor

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