waterbycounty
Federal water data

County water report

St. Mary Parish Water Report

Drinking-water compliance, watershed health, monitoring records, and river conditions for St. Mary Parish, Louisiana.

Water grade

F

Water score

14.4

State rank

#43

of 63

Health violations

131

EPA SDWIS, 5-year lookback

Watershed impaired

85.7%

119 water bodies assessed

Monitoring sites

43

15,591 recent measurements

Live streamflow

130%

Wax Lake Outlet at Calumet, LA

Water at a glance

Key Water Indicators for St. Mary Parish

EPA SDWIS

Safety Grade

F

Score: 14.4 / 100

EPA SDWIS

Active Violations

131

5-year health-based lookback

EPA ATTAINS

Watershed Health

86% impaired

119 bodies assessed

USGS NWIS

Streamflow Snapshot

130% of mean

Wax Lake Outlet at Calumet, LA

EPA WQP

Monitoring Sites

43

15,591 recent readings

Source: EPA SDWIS · Safe Drinking Water Information System

Drinking Water Compliance

Compliance grade

F

Based on EPA SDWIS compliance history.

Water score

Higher scores indicate cleaner recent compliance records.

14.4/100

Health violations

131

Health-based violations

Violations per 100K served

209.2

Population-normalized SDWIS rate

Editorial analysis

Understanding St. Mary Parish’s Water

Drinking Water Quality Overview

EPA SDWIS

St. Mary Parish's water systems carry a failing grade, scoring 14.4 out of 100. Over the past five years, EPA SDWIS records 131 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 large majority — 85.7% — of assessed waterways are impaired (102 of 119 water bodies) across St. Mary Parish's watersheds. The leading impairment causes are dissolved oxygen and fecal coliform. 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 2026-05-14T13:45:00.000-05:00) puts Wax Lake Outlet at 126.0k cfs — flowing above its historical average at 130% 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. St. Mary Parish has moderate coverage with 43 active monitoring sites with 15,591 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 St. Mary Parish

Water Verdict

St. Mary Parish, Louisiana receives a poor water quality assessment with a grade of F and a score of 14.4 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. Separately, EPA ATTAINS assessments cover 119 water bodies in the county's watershed, with 85.7% 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 running above its historical mean at 130.4%.

Violation Context

EPA SDWIS records for St. Mary Parish, Louisiana show 131 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 209.2 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: 15,591 water-quality results have been logged across the county in the EPA Water Quality Portal over the past five years.

Consumer Guidance

St. Mary Parish has a Grade F compliance record with 131 health-based violations — among the highest levels in the country. St. Mary Parish's drinking-water compliance score is 14.4 out of 100. 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 Louisiana Department of Environmental Quality or Health can expedite utility compliance action. Dissolved Oxygen is the leading impairment cause in St. Mary Parish's watershed. With 43 active water-quality monitoring sites in St. Mary Parish, data coverage is strong. A pipeline streamflow snapshot from the Wax Lake Outlet gauge is also available on this page.

Regional Context

St. Mary Parish has poorer water quality than the average county in Louisiana. Its water score is 15.7 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 St. Mary Parish's water environment

Watershed Impairment Causes (EPA ATTAINS)

  • 1

    Low dissolved oxygen

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

  • 2

    Fecal coliform bacteria

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

  • 3

    Enterococcus bacteria

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

Source: EPA ATTAINS · Reporting cycle 2022

Official EPA Resources for St. Mary Parish

EPA How's My Waterway

Interactive watershed health data for St. Mary Parish

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for St. Mary Parish

Consumer Confidence Reports (LA)

Annual water quality reports from utilities in Louisiana

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

85.7%

102 of 119 assessed

High concern

Top Impairment Causes

  • 1

    DISSOLVED OXYGEN

  • 2

    FECAL COLIFORM

  • 3

    ENTEROCOCCUS

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

43

Active in the past 5 years

Measurements Recorded

16K

15,591 total readings

Most Measured

  • Physical
  • Organics, Other
  • 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

126.0Kcfs

May 14, 6:45 PM UTC

vs Long-Term Average

130%

Well above typical

Primary Streamgage

Wax Lake Outlet at Calumet, LA

USGS site
07381590
Long-term mean
96.7K 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

3

3 people  ·  ~225 gal/day

Annual Total

$558

Monthly

$47

Water Bill

$558/yr

Filter Cost

$0/yr

Safety Grade for St. Mary Parish: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.

Try the full calculator →

Improve your water quality at home

Berkey filters remove 99.9%+ of contaminants from tap water.

Shop Berkey →

Sponsored

Test your tap water

Tap Score provides professional mail-in water testing.

Get Tested →

Frequently Asked Questions

What is the water quality in St. Mary Parish, Louisiana?
St. Mary Parish, Louisiana has a drinking-water quality grade of F with a score of 14.4/100, based on EPA SDWIS compliance data. The county has 131 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 St. Mary Parish?
St. Mary Parish has 131 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 St. Mary Parish?
EPA ATTAINS assessments under Clean Water Act §303(d) indicate 85.7% of St. Mary Parish's 119 assessed water bodies are classified as impaired (102 impaired). The top reported causes are DISSOLVED OXYGEN, FECAL COLIFORM, ENTEROCOCCUS. 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 St. Mary Parish?
EPA's Water Quality Portal records 15,591 measurements from 43 monitoring sites in St. Mary Parish over the past five years. The most frequently measured characteristic groups are Physical, Organics, Other, 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 St. Mary Parish right now?
St. Mary Parish's primary USGS streamgage on the Wax Lake Outlet has a pipeline snapshot of 126,000 cubic feet per second — 130% of the long-term mean of 96,655 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 St. Mary Parish water compare to the Louisiana average?
St. Mary Parish's SDWIS water quality score of 14.4/100 is lower than the Louisiana state average of 30.1. The average water quality grade across Louisiana is F, based on data from 63 counties with available SDWIS data.
Is tap water safe to drink in St. Mary Parish?
Based on EPA SDWIS data, St. Mary Parish has a water quality grade of F (14.4/100). 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 St. Mary Parish have so many water violations?
St. Mary Parish has 131 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 St. Mary Parish rank for water quality in Louisiana?
St. Mary Parish ranks #43 out of 63 counties in Louisiana by SDWIS water quality score (1 = best). With a score of 14.4/100, 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

Iberville Parish

Louisiana

F

14.1

Water score

Madison Parish

Louisiana

F

14.0

Water score

Acadia Parish

Louisiana

F

16.0

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

Explore more data for St. Mary Parish

Property TaxCost of LivingCrime RateIncomeHealthSchoolsDisaster RiskWeatherCounty Score