County water report

Middlesex County Water Report

Drinking-water compliance, watershed health, monitoring records, and river conditions for Middlesex County, Massachusetts.

Water grade

Water score

68.0

State rank

of 14

Health violations

EPA SDWIS, 5-year lookback

Watershed impaired

Not reported

EPA ATTAINS coverage varies by state

Monitoring sites

265

61,571 recent measurements

Live streamflow

73%

MERRIMACK RIVER BL CONCORD RIVER AT LOWELL, MA

Water at a glance

Key Water Indicators for Middlesex County

EPA SDWIS

Safety Grade

Score: 68.0 / 100

EPA SDWIS

Active Violations

5-year health-based lookback

EPA ATTAINS

Watershed Health

Not reported

Coverage varies by state

USGS NWIS

Streamflow Snapshot

73% of mean

MERRIMACK RIVER BL CONCORD RIVER AT LOWELL, MA

EPA WQP

Monitoring Sites

265

61,571 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.

68.0/100

Health violations

Health-based violations

Violations per 100K served

1.9

Population-normalized SDWIS rate

Data center water stress

Middlesex County has 16 facilities in the DCWSI dataset.

ByCounty's DCWSI ranks this county #44 nationally by combining its water score with mapped data center density.

DCWSI

77.4

0-100 index

Facility count

91.5 density percentile

Discharge estimate

Not reported

EPA CWA fields where available

Water vs median

+18.0

Compared with US county median

Named operators

AWS

Mapped facilities

35 MCGRATH REALTY LLC
SOMERVILLE
EPA ECHO
580 WINTER STREET LLC
WALTHAM
EPA ECHO
AMAZON COM SERVICES LLC DKO1
LITTLETON · Amazon Data Services
EPA ECHO
AMAZON.COM LLC - DK01
LITTLETON · Amazon Data Services
EPA ECHO
CoreSite BO1
Somerville · CoreSite
OSM
EQUINIX
BILLERICA · Equinix
EPA ECHO

10 more mapped facilities included in the county score.

See the Middlesex County data-center report Review methodology

Data Center Water Budget Calculator

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

Facility size: 100 MW

1 MW1,000 MW

Cooling type

Utilization: 70%

40%100%

799K gallons/dayModerate Impact

Your facility would use 6.5% of this county's industrial water baseline — manageable but worth monitoring against drought trends.

6.5% of county industrial baseline11.51 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 Middlesex County’s Water

Drinking Water Quality Overview

EPA SDWIS

Middlesex County earns a B grade for drinking water quality, scoring 68.0 out of 100. Over the past five years, EPA SDWIS records 30 health-based violations — a pattern that public water utilities are required to disclose and correct.

River & Streamflow Status

USGS NWIS

USGS NWIS gauge data (as of 2026-05-14T14:30:00.000-04:00) puts MERRIMACK RIVER BL CONCORD RIVER at 5.8k cfs — running somewhat below its historical average at 73% 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. Middlesex County has extensive coverage with 265 active monitoring sites with 61,571 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 Middlesex County

Water Verdict

Middlesex County, Massachusetts receives a fair water quality assessment with a grade of B and a score of 68.0 out of 100. The water supply meets baseline federal standards, but there may be periods of elevated contaminant levels or infrastructure concerns worth monitoring. The county's primary USGS gauge drains roughly 4,635 square miles of upstream watershed, giving local source waters a regional footprint. At the most recent USGS reading, local streamflow was below its historical mean at 72.8% — worth watching in drier seasons.

Violation Context

EPA SDWIS records for Middlesex County, Massachusetts show 30 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 1.9 violations per 100,000 people served, this rate is relatively low compared to many U.S. counties. This compliance record sits alongside an unusually deep monitoring archive: 61,571 water-quality results have been logged across the county in the EPA Water Quality Portal over the past five years.

Consumer Guidance

Tap water in Middlesex County meets baseline safety standards, though the compliance record shows some violations worth watching. Middlesex County's drinking-water compliance score is 68.0 out of 100. The violation rate for Middlesex County is 1.9 per 100,000 people served. Running tap water for 30 seconds before drinking can reduce any localized lead exposure from household plumbing. Requesting your utility's most recent Consumer Confidence Report is the fastest way to identify which specific contaminants were flagged. With 265 active water-quality monitoring sites in Middlesex County, data coverage is strong. A pipeline streamflow snapshot from the MERRIMACK RIVER BL CONCORD RIVER gauge is also available on this page.

Regional Context

Middlesex County has water quality close to the average county in Massachusetts. Its water score is within 1.1 points of the state average, meaning its overall water system performance is broadly representative of Massachusetts as a whole.

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 Middlesex County's water environment

Official EPA Resources for Middlesex County

EPA How's My Waterway

Interactive watershed health data for Middlesex County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Middlesex County

Consumer Confidence Reports (MA)

Annual water quality reports from utilities in Massachusetts

Past 5 years

Water Quality Monitoring

Monitoring Sites

265

Active in the past 5 years

Measurements Recorded

62K

61,571 total readings

Most Measured

Physical
Nutrient
Inorganics, Major, Non-metals

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

5,830cfs

May 14, 6:30 PM UTC

vs Long-Term Average

73%

Below typical

Primary Streamgage

MERRIMACK RIVER BL CONCORD RIVER AT LOWELL, MA

USGS site: 01100000
Drainage area: 4,635 sq mi
Long-term mean: 8,008 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 Middlesex 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 Middlesex County, Massachusetts?

Middlesex County, Massachusetts has a drinking-water quality grade of B with a score of 68.0/100, based on EPA SDWIS compliance data. The county has 30 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 Middlesex County?

Middlesex County has 30 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 Middlesex County?

EPA's Water Quality Portal records 61,571 measurements from 265 monitoring sites in Middlesex County over the past five years. The most frequently measured characteristic groups are Physical, Nutrient, Inorganics, Major, Non-metals. 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 Middlesex County right now?

Middlesex County's primary USGS streamgage on the MERRIMACK RIVER BL CONCORD RIVER has a pipeline snapshot of 5,830 cubic feet per second — 73% of the long-term mean of 8,008.48 cfs. Flow is within typical range for this gauge. For the latest gauge feed, visit waterdata.usgs.gov.

How does Middlesex County water compare to the Massachusetts average?

Middlesex County's SDWIS water quality score of 68.0/100 is lower than the Massachusetts state average of 69.1. The average water quality grade across Massachusetts is C, based on data from 14 counties with available SDWIS data.

Is tap water safe to drink in Middlesex County?

Based on EPA SDWIS data, Middlesex County has a water quality grade of B (68.0/100). 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).

Why does Middlesex County have so many water violations?

Middlesex County has 30 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 Middlesex County rank for water quality in Massachusetts?

Middlesex County ranks #6 out of 14 counties in Massachusetts by SDWIS water quality score (1 = best). With a score of 68.0/100, 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

Hampshire County

Massachusetts

67.5

Water score

Hampden County

Massachusetts

66.4

Water score

Essex County

Massachusetts

70.4

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 Evan Brooks, Data EditorUpdated May 14, 2026Reviewed by Evan Brooks, Data Editor

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