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Maryland water profile

Nitrate in Maryland community water systems

Maryland is really three states for nitrate: a high-risk Delmarva Eastern Shore, a mixed carbonate Piedmont, and a generally low western Appalachian region. See where higher public-system results concentrate and what each reporting system measured in the three years from August 9, 2023 to August 9, 2026.

Browse all 458 Maryland systems →

Search by the utility or system name shown on a water bill. Example: Washington Suburban Sanitary Commission. Private wells are not in this inventory.

99%
of the state’s 463 active community water systems have a current result here
458
systems with a current nitrate result
5,524,944
people served by those reporting systems
7.0%
of reporting systems at or above 5 mg/L
How to read these numbers Each system is placed into a band by its most recent reported result within a rolling three-year window. The bands describe how strongly human activity, read from nitrate, has marked a water source; they are not a safety verdict. Figures describe system reporting, not nitrate measured at an individual tap.

How Maryland's systems fall across the five bands

Most systems report below 3 mg/L

Natural background
0.00–0.99 mg/L as N
272 systems · 1,009,353 served
Human impact likely
1.00–2.99 mg/L as N
110 systems · 4,220,561 served
Human impact clear
3.00–4.99 mg/L as N
44 systems · 190,640 served
Health-study range
5.00–9.99 mg/L as N
31 systems · 104,325 served
Above the federal limit
10.00 mg/L and above
1 system · 65 served

Each system appears in one band only, placed by its most recent reported result in the current three-year window. Counts sit beside people served so a small number of larger systems cannot hide behind a row of tiny ones. Of the 32 systems reporting 5 mg/L or more, 17 stayed at or above 5 across the whole three-year range; the other 15 reached it only on a high sample and otherwise ran lower.

Most recent reading Jul 2026; the typical system was last tested around Jan 2026. 421 systems sampled their own water; 37 systems carry a supplier’s result.

The named systems

Every reading here belongs to a utility with a name

Highest recent readings
SystemMost recent resultBandBased onPeople served
Woodland Trailer Park10.80 mg/LApr 2026a high point — runs lowerAbove the federal limit26 samples65
Town Of Walkersville9.94 mg/LMay 2026a high point — runs lowerHealth-study range18 samples8,440
Benedictine School9.40 mg/LApr 2026a high point — runs lowerHealth-study range15 samples300
Boh-Nak Mobile Home Park8.40 mg/LJul 2025Health-study range8 samples85
Town Of Hampstead8.27 mg/LJun 2026a high point — runs lowerHealth-study range124 samples6,600
Gaither Manor Apartments8.10 mg/LApr 2026Health-study range12 samples450
Chapel Hill Nursing Center7.84 mg/LApr 2026Health-study range9 samples125
Elkton West7.70 mg/LApr 2026a high point — runs lowerHealth-study rangeinherited from supplier3,500
Largest systems
SystemMost recent resultBandBased onPeople served
Washington Suburban Sanitary Commission1.15 mg/LMay 2026Human impact likely68 samples1,900,000
City Of Baltimore1.12 mg/LJul 2025Human impact likely9 samples1,600,000
Glen Burnie-Broadneck0.50 mg/LJul 2025Natural background12 samples290,606
Howard County D.P.W. Distribution1.15 mg/LMay 2026Human impact likelyinherited from supplier286,158
Harford County D.P.W.3.56 mg/LMay 2026a high point — runs lowerHuman impact clear19 samples104,567

Each result shows its date and what it rests on, so a lone sample is never taken for a settled measurement. A single high sample is not a complete account of what a household drinks.

Where higher nitrate concentrates

Higher results gather on the carbonate Piedmont and the Eastern Shore

Human impact is clear on drinking water served in 15 of Maryland’s 24 counties. Each is shaded by how many of its systems reported 3.00 mg/L as N or above. Shading counts systems, not severity — a county with many small utilities can outrank one holding a single larger system that reads higher. The table beside the map splits the two bands so that difference stays visible.

MD counties shaded by number of community water systems reporting nitrate at or above 3.00 mg/L as NCounties are shaded by how many community water systems reported nitrate at or above 3.00 mg/L as N in the three years from August 9, 2023 to August 9, 2026. The same counts appear in the table below this map.Washington County — 3 systems at 3.00–4.99 mg/L as N; 2 systems at 5.00 mg/L as N or aboveCaroline County — 0 systems at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveWicomico County — 3 systems at 3.00–4.99 mg/L as N; 5 systems at 5.00 mg/L as N or aboveCarroll County — 8 systems at 3.00–4.99 mg/L as N; 9 systems at 5.00 mg/L as N or aboveDorchester County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveGarrett County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveKent County — 0 systems at 3.00–4.99 mg/L as N; 2 systems at 5.00 mg/L as N or aboveMontgomery County — 0 systems at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveCecil County — 8 systems at 3.00–4.99 mg/L as N; 2 systems at 5.00 mg/L as N or aboveHoward County — 0 systems at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveWorcester County — 3 systems at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveAnne Arundel County — 2 systems at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveHarford County — 7 systems at 3.00–4.99 mg/L as N; 2 systems at 5.00 mg/L as N or aboveBaltimore County — 3 systems at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveFrederick County — 5 systems at 3.00–4.99 mg/L as N; 6 systems at 5.00 mg/L as N or above
none1–23–56–1112–2526+Number of drinking water systems reporting ≥3.00 mg/L NO₃–N per county as of August 9, 2026

Carroll leads this layer with 9 reporting systems, followed by Frederick, Wicomico, Cecil. Higher results gather on the carbonate Piedmont and the Eastern Shore.

Counties with the most systems at or above 3 mg/L as N
County3–4.99≥5Total ≥3
Carroll8917
Frederick5611
Cecil8210
Harford729
Wicomico358

Counts use each system's most recent reported result in the current three-year window. A system appears in only one of the two bands.

Find a specific Maryland system

What the statewide pattern says

Three Marylands for nitrate

Maryland's higher nitrate splits by geology: the Delmarva Eastern Shore's oxic sand under poultry and row crops, the carbonate valleys of the Piedmont, and a generally low Appalachian west.

The Eastern Shore, east of the Chesapeake, is the high-risk part, and it is the Delmarva story — oxygen-rich surficial sand under poultry and row crops, with nitrate persisting to depth and moving through groundwater toward the Bay (Ator and Denver, 2015) (Nolan and Hitt, 2006).

Central Maryland's Piedmont is fractured crystalline and carbonate rock, where risk is local: the carbonate valleys around Frederick and Hagerstown can run higher where farming overlies them, while crystalline-rock wells vary. The public-system map reflects exactly that — Carroll and Frederick counties in the Piedmont carbonate belt carry the most higher-band systems, with the Eastern Shore counties behind them.

Western, Appalachian Maryland is generally lower, except over its own agricultural carbonate valleys. The supported source reading is agricultural — poultry-manure-heavy on the Shore, mixed farm nitrogen on the Piedmont carbonate — not a certified source at any individual system. Across all of it, the groundwater carrying nitrate on the Eastern Shore is a major route delivering it to the Chesapeake, on the slow, decades-long clock that governs groundwater everywhere (Dubrovsky and others, 2010).

The general science — how nitrate moves, why some ground is vulnerable, and why the legacy lingers — is laid out with its sources on Where nitrate comes from.

Questions this page answers

What the Maryland pattern does—and does not—say

Where does nitrate concentrate in Maryland community water systems?

Carroll leads this layer with 9 reporting systems, followed by Frederick, Wicomico, Cecil. Higher results gather on the carbonate Piedmont and the Eastern Shore.

Which part of Maryland carries the nitrate risk?

Two parts: the Delmarva Eastern Shore, oxic surficial sand under poultry and row crops, and the carbonate valleys of the Piedmont around Frederick and Hagerstown where farming overlies fractured limestone. Western Appalachian Maryland is generally lower.

Can this page say the source is agriculture?

At the zone level, yes — carefully: poultry-manure-heavy on the Eastern Shore, mixed farm nitrogen on the Piedmont carbonate. The evidence does not certify a source at each individual system.

Does a high public-system result mean a nearby private well is high?

No. It is a local sentinel, not a well-specific result. It shows that nitrogen and a transport pathway have reached groundwater in the area; a certified-lab test is still the only way to know a specific private well.

Sources and provenance

What this page rests on

  1. NitrateSmart inventory: 458 Maryland community water systems with a current nitrate result in the three years from August 9, 2023 to August 9, 2026. Figures count people served by reporting systems, not measured tap exposure.
  2. Nolan BT, Hitt KJ (2006). Vulnerability of Shallow Groundwater and Drinking-Water Wells to Nitrate in the United States. Environmental Science & Technology 40(24):7834–7840.
  3. Dubrovsky NM, and others (2010). Nutrients in the Nation's Streams and Groundwater, 1992–2004. USGS Circular 1350.
  4. Ator SW, Denver JM (2015). Understanding nutrients in the Chesapeake Bay watershed and implications for management and restoration — the Eastern Shore. USGS Circular 1406.
  5. Denver JM (1993). Water-quality assessment of the Delmarva Peninsula — effects of agricultural activities on nitrate in the surficial aquifer. USGS Open-File Report 93-40.