County water report

Montgomery County Water Report

Drinking-water compliance, watershed health, monitoring records, and river conditions for Montgomery County, Maryland.

Water grade

Water score

86.0

State rank

of 24

Health violations

EPA SDWIS, 5-year lookback

Watershed impaired

33.3%

60 water bodies assessed

Monitoring sites

22,829 recent measurements

Live streamflow

24%

POTOMAC RIVER NEAR WASH, DC LITTLE FALLS PUMP STA

Water at a glance

Key Water Indicators for Montgomery County

EPA SDWIS

Safety Grade

Score: 86.0 / 100

EPA SDWIS

Active Violations

5-year health-based lookback

EPA ATTAINS

Watershed Health

33% impaired

60 bodies assessed

USGS NWIS

Streamflow Snapshot

24% of mean

POTOMAC RIVER NEAR WASH, DC LITTLE FALLS PUMP STA

EPA WQP

Monitoring Sites

22,829 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.

86.0/100

Health violations

Health-based violations

Violations per 100K served

0.0

Population-normalized SDWIS rate

Data center water stress

Montgomery County has 6 facilities in the DCWSI dataset.

ByCounty's DCWSI ranks this county #16 nationally by combining its water score with mapped data center density.

DCWSI

82.0

0-100 index

Facility count

76.0 density percentile

Discharge estimate

Not reported

EPA CWA fields where available

Water vs median

+36.0

Compared with US county median

Named operators

Lincoln Rackhouse

Mapped facilities

ADP OF WASHINGTON
ROCKVILLE
EPA ECHO
GANNETT COMPANY
SILVER SPRING
EPA ECHO
GE INFORMATION SYSTEMS
GAITHERSBURG
EPA ECHO
GENERAL ELECTRIC, ROCKVILLE
ROCKVILLE
EPA ECHO
Lincoln Rackhouse Maryland
Silver Spring · Lincoln Rackhouse
OSM
PROSPERITY DRIVE DATA CENTER, LLC
SILVER SPRING
EPA ECHO

See the Montgomery County data-center report Review methodology

Data Center Water Budget Calculator

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

Facility size: 100 MW

1 MW1,000 MW

Cooling type

Utilization: 70%

40%100%

799K gallons/dayHigh Impact

Your facility would use 72.5% of this county's industrial water baseline. Verify water rights and long-term drought projections before committing.

72.5% of county industrial baseline0.30 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 Montgomery County’s Water

Drinking Water Quality Overview

EPA SDWIS

Montgomery County earns an A grade for drinking water quality, scoring 86.0 out of 100. EPA's Safe Drinking Water Information System (SDWIS) records zero health-based violations over the past five years — a strong compliance signal for a mid-sized county.

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 substantial 33.3% of assessed waterways are impaired (20 of 60 water bodies) across Montgomery County's watersheds. The leading impairment causes are total suspended solids (tss) and phosphorus, total. 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 2026-05-14T14:50:00.000-04:00) puts POTOMAC RIVER at 2.8k cfs — well below its long-term average at 24% of mean — low-flow conditions worth noting for water-dependent ecosystems. 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. Montgomery County has moderate coverage with 27 active monitoring sites with 22,829 recent measurements on record. Predominant monitoring categories include physical and nutrient. 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 Montgomery County

Water Verdict

Montgomery County, Maryland receives an excellent water quality assessment with a grade of A and a score of 86.0 out of 100. The water supply meets or exceeds federal safety standards, and residents can generally drink tap water with confidence. Separately, EPA ATTAINS assessments cover 60 water bodies in the county's watershed, with 33.3% 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 24.4% — worth watching in drier seasons.

Violation Context

EPA SDWIS records for Montgomery County, Maryland show zero health-based violations, indicating that the county's water systems met all federal safety standards during the reporting period. The violation rate is zero per 100,000 people served, which is the best possible outcome. This compliance record sits alongside an unusually deep monitoring archive: 22,829 water-quality results have been logged across the county in the EPA Water Quality Portal over the past five years.

Consumer Guidance

The EPA compliance record for Montgomery County shows no recent health-based violations. No health-based violations have been recorded, placing Montgomery County in the top tier for drinking-water safety. Montgomery County's drinking-water compliance score is 86.0 out of 100. As a routine precaution, requesting your utility's annual Consumer Confidence Report each July gives you a full list of detected contaminants and their treatment levels. With 27 active water-quality monitoring sites in Montgomery County, data coverage is strong. A pipeline streamflow snapshot from the POTOMAC RIVER gauge is also available on this page.

Regional Context

Montgomery County has better water quality than the average county in Maryland. Its water score is 35.5 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 Montgomery County's water environment

Watershed Impairment Causes (EPA ATTAINS)

1
Total Suspended Solids (Tss)
Impairment cause per EPA Clean Water Act §303(d) assessment
2
Phosphorus (excess nutrients)
Impairment cause per EPA Clean Water Act §303(d) assessment
3
Elevated temperature
Impairment cause per EPA Clean Water Act §303(d) assessment

Source: EPA ATTAINS · Reporting cycle 2022

Official EPA Resources for Montgomery County

EPA How's My Waterway

Interactive watershed health data for Montgomery County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Montgomery County

Consumer Confidence Reports (MD)

Annual water quality reports from utilities in Maryland

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

33.3%

20 of 60 assessed

Moderate concern

Top Impairment Causes

1
TOTAL SUSPENDED SOLIDS (TSS)
2
PHOSPHORUS, TOTAL
3
TEMPERATURE

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

Active in the past 5 years

Measurements Recorded

23K

22,829 total readings

Most Measured

Physical
Nutrient
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

2,800cfs

May 14, 6:50 PM UTC

vs Long-Term Average

24%

Well below typical

Primary Streamgage

POTOMAC RIVER NEAR WASH, DC LITTLE FALLS PUMP STA

USGS site: 01646500
Drainage area: 11,560 sq mi
Long-term mean: 11.5K 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 Montgomery 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.

Try the full calculator →

Montgomery County has good water quality

Learn about water restrictions and conservation in your area.

Water Restrictions →

Frequently Asked Questions

What is the water quality in Montgomery County, Maryland?

Montgomery County, Maryland has a drinking-water quality grade of A with a score of 86.0/100, based on EPA SDWIS compliance data. The county has 0 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 Montgomery County?

Montgomery County has 0 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). Zero violations is an excellent record indicating consistent compliance with federal drinking water standards.

How healthy are the watersheds in Montgomery County?

EPA ATTAINS assessments under Clean Water Act §303(d) indicate 33.3% of Montgomery County's 60 assessed water bodies are classified as impaired (20 impaired). The top reported causes are TOTAL SUSPENDED SOLIDS (TSS), PHOSPHORUS, TOTAL, TEMPERATURE. 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 Montgomery County?

EPA's Water Quality Portal records 22,829 measurements from 27 monitoring sites in Montgomery County over the past five years. The most frequently measured characteristic groups are Physical, Nutrient, 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 Montgomery County right now?

Montgomery County's primary USGS streamgage on the POTOMAC RIVER has a pipeline snapshot of 2,800 cubic feet per second — 24% of the long-term mean of 11,480.23 cfs. This is well below typical — often a signal of drought stress on source water. For the latest gauge feed, visit waterdata.usgs.gov.

How does Montgomery County water compare to the Maryland average?

Montgomery County's SDWIS water quality score of 86.0/100 is higher than the Maryland state average of 50.5. The average water quality grade across Maryland is D, based on data from 24 counties with available SDWIS data.

Is tap water safe to drink in Montgomery County?

Based on EPA SDWIS data, Montgomery County has a water quality grade of A (86.0/100). This indicates good to excellent water quality with strong SDWIS compliance. 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 Montgomery County have clean drinking water?

Montgomery County has 0 health-based drinking water violations according to EPA records. With a water quality score of 86.0/100 and grade A, the county's drinking water meets EPA standards with no recorded health violations. 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 Montgomery County rank for water quality in Maryland?

Montgomery County ranks #1 out of 24 counties in Maryland by SDWIS water quality score (1 = best). With a score of 86.0/100, 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

Baltimore city

Maryland

71.8

Water score

Howard County

Maryland

70.6

Water score

Anne Arundel County

Maryland

67.5

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 May 14, 2026Reviewed by Evan Brooks, Data Editor

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