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New York water profile

Nitrate in New York community water systems

New York's nitrate has a capital: Long Island, where a sole-source aquifer under nearly three million people has been absorbing cesspool and fertilizer nitrogen for a century. See where the pattern concentrates and what each reporting system measured in the three years from August 9, 2023 to August 9, 2026.

Browse all 424 New York systems →

Search by the utility or system name shown on a water bill. Example: Suffolk County Water Authority. Private wells are not in this inventory.

19%
of the state’s 2,247 active community water systems have a current result here
424
systems with a current nitrate result
11,909,361
people served by those reporting systems
6.8%
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 New York's systems fall across the five bands

Most systems report below 3 mg/L

Natural background
0.00–0.99 mg/L as N
305 systems · 10,115,502 served
Human impact likely
1.00–2.99 mg/L as N
67 systems · 197,222 served
Human impact clear
3.00–4.99 mg/L as N
23 systems · 82,181 served
Health-study range
5.00–9.99 mg/L as N
26 systems · 1,513,652 served
Above the federal limit
10.00 mg/L and above
3 systems · 804 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 29 systems reporting 5 mg/L or more, 12 stayed at or above 5 across the whole three-year range; the other 17 reached it only on a high sample and otherwise ran lower.

Most recent reading Dec 2025; the typical system was last tested around Jun 2024. 331 systems sampled their own water; 93 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
Benton Wd #114.80 mg/LAbove the federal limitCCR summary, unverified400
Benton Wd #314.80 mg/LAbove the federal limitCCR summary, unverified332
Pine Village Estates Mhp10.61 mg/LAbove the federal limitCCR summary, unverified72
Suffolk County Water Authority9.66 mg/La high point — runs lowerHealth-study rangeCCR summary, unverified1,100,000
Greenlawn Water District8.10 mg/LFeb 2024a high point — runs lowerHealth-study rangeCCR summary, unverified42,000
Pine Tree Mobile Home Park7.61 mg/LHealth-study rangeCCR summary, unverified44
Village Park Apartments7.40 mg/LHealth-study rangeCCR summary, unverified500
Idle Wheels Manufactured Home Community7.00 mg/LHealth-study rangeCCR summary, unverified150
Largest systems
SystemMost recent resultBandBased onPeople served
New York City System0.39 mg/LNatural backgroundCCR summary, unverified8,271,000
Suffolk County Water Authority9.66 mg/La high point — runs lowerHealth-study rangeCCR summary, unverified1,100,000
Ocwa0.18 mg/LNatural backgroundCCR summary, unverified350,000
Veolia Water New York, Inc. Rd-10.39 mg/LNatural backgroundinherited from supplier146,732
Mvwa - Mohawk Valley Water Authority0.19 mg/LFeb 2024Natural backgroundCCR summary, unverified126,250

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

Long Island leads, with an upstate scatter

Human impact is clear on drinking water served in 19 of New York’s 62 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.

NY 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.Oswego County — 0 systems at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveNassau County — 2 systems at 3.00–4.99 mg/L as N; 9 systems at 5.00 mg/L as N or aboveHerkimer County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveOrange County — 2 systems at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveOnondaga County — 1 system at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveSuffolk County — 2 systems at 3.00–4.99 mg/L as N; 3 systems at 5.00 mg/L as N or aboveChemung County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveOneida County — 0 systems at 3.00–4.99 mg/L as N; 2 systems at 5.00 mg/L as N or aboveOtsego County — 0 systems at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or abovePutnam County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveColumbia County — 2 systems at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveCattaraugus County — 0 systems at 3.00–4.99 mg/L as N; 5 systems at 5.00 mg/L as N or aboveRensselaer County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveSaratoga County — 2 systems at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveDutchess County — 3 systems at 3.00–4.99 mg/L as N; 2 systems at 5.00 mg/L as N or aboveCayuga County — 3 systems at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveCortland County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveWashington County — 0 systems at 3.00–4.99 mg/L as N; 2 systems at 5.00 mg/L as N or aboveYates County — 0 systems at 3.00–4.99 mg/L as N; 2 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

Nassau leads this layer with 9 reporting systems, followed by Cattaraugus, Suffolk, Dutchess. Long Island leads, with an upstate scatter. Coverage note: the map places 99% of New York’s reporting systems. Of the rest, 2 carry a supplier’s result measured elsewhere and belong off this map; 1 sampled their own water and are missing a county in the records, so the map reads as a floor by at least that much.

Counties with the most systems at or above 3 mg/L as N
County3–4.99≥5Total ≥3
Nassau2911
Cattaraugus055
Dutchess325
Suffolk235
Cayuga303

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. Coverage note: the map places 99% of New York’s reporting systems. Of the rest, 2 carry a supplier’s result measured elsewhere and belong off this map; 1 sampled their own water and are missing a county in the records, so the map reads as a floor by at least that much.

Find a specific New York system

What the statewide pattern says

A sole-source aquifer under suburbia

New York's documented nitrate center is Long Island's sole-source aquifer — septic and cesspool nitrogen in the suburbs, fertilizer in the east-end farm belt — with a thinner dairy-country signal upstate.

Long Island drinks only groundwater, and USGS has tracked its nitrate since the 1970s: the upper glacial aquifer, the water-table layer, takes nitrogen directly from cesspools, septic tanks, lawn fertilizer and storm runoff (USGS Water-Resources Investigations Report 78-41). Isotope work in Suffolk County confirms the source mix — fertilizer, septic effluent and animal waste — and in the east-end farm belt, test-farm wells have run 10 to 30 mg/L from fertilizer alone (USGS SIR 2025-5010).

The deeper Magothy aquifer, which supplies most public water, starts cleaner — but pumping drags shallow nitrate down into it, which is why Long Island utilities blend and treat, and why Nassau and Suffolk still anchor this page's map. In the village of Patchogue, one shallow well reached 40 mg/L beside the Patchogue River (USGS SIR 2010-5132).

Upstate reads differently: Cattaraugus County's showing sits in western New York dairy-and-fractured-rock country, and Dutchess and Columbia counties mix fractured bedrock with septic — settings the Long Island literature does not cover, so this page marks the signal without claiming a certified source for them.

The supported source reading is on-site wastewater first, fertilizer second, on Long Island; mixed and less-studied upstate — not a certified source at any individual system (Nolan and Hitt, 2006).

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 New York pattern does—and does not—say

Where does nitrate concentrate in New York community water systems?

Nassau leads this layer with 9 reporting systems, followed by Cattaraugus, Suffolk, Dutchess. Long Island leads, with an upstate scatter.

Why does Long Island dominate New York's nitrate map?

It has no alternative water source and no dilution: a sole-source aquifer under nearly three million people, recharged only by local precipitation. A century of cesspools, septic systems, lawn fertilizer and — in the east — intensive farming recharges straight into the water table. USGS has documented rising nitrate there since the 1970s.

Is deep public water on Long Island safe from the shallow nitrate?

Mostly, but not automatically. The deeper Magothy aquifer starts cleaner, yet USGS found that pumping draws shallow, nitrate-bearing water downward into it. That is why Long Island suppliers monitor, blend and in places treat — and why the island invests in sewering and fertilizer rules.

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: 424 New York 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. USGS (1978). Chemical quality of ground water in Nassau and Suffolk Counties, Long Island. Water-Resources Investigations Report 78-41 — sole-source aquifer; nitrate from cesspools, septic tanks, fertilizers and storm runoff.
  5. USGS (2025). Stream water quality and groundwater levels in the Central Pine Barrens, Suffolk County. Scientific Investigations Report 2025-5010 — isotope sources fertilizer, septic effluent, animal waste; pumping draws nitrate toward the Magothy.
  6. USGS (2010). Shallow groundwater quality in the Village of Patchogue, Suffolk County. SIR 2010-5132 — one well at 40 mg/L; sources fertilizer, septic waste and animal waste.