Delaware
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Delaware water profile

Nitrate in Delaware community water systems

Delaware sits on the Delmarva Peninsula's shallow sand aquifer, one of the more nitrate-vulnerable settings in the country, and its defining source is not corn — it is poultry. Higher public-system results concentrate in Sussex County. See what each reporting system measured in the three years from August 9, 2023 to August 9, 2026.

Browse all 207 Delaware systems →

Search by the utility or system name shown on a water bill. Example: City of Dover Water. Private wells are not in this inventory.

100%
of the state’s 207 active community water systems have a current result here
207
systems with a current nitrate result
1,022,142
people served by those reporting systems
16.9%
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 Delaware's systems fall across the five bands

Most systems report below 3 mg/L

Natural background
0.00–0.99 mg/L as N
119 systems · 248,102 served
Human impact likely
1.00–2.99 mg/L as N
24 systems · 270,738 served
Human impact clear
3.00–4.99 mg/L as N
29 systems · 193,890 served
Health-study range
5.00–9.99 mg/L as N
33 systems · 309,130 served
Above the federal limit
10.00 mg/L and above
2 systems · 282 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 35 systems reporting 5 mg/L or more, 9 stayed at or above 5 across the whole three-year range; the other 26 reached it only on a high sample and otherwise ran lower.

Most recent reading Jun 2026; the typical system was last tested around Mar 2026. 197 systems sampled their own water; 10 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
Fish Hook Mobile Home Park18.67 mg/LJun 2026a high point — runs lowerAbove the federal limit34 samples72
Crosswinds Mhp, Llc10.73 mg/LApr 2026a high point — runs lowerAbove the federal limit12 samples210
Cherry Creek Valley9.26 mg/LJun 2026Health-study range37 samples78
Love Creek Mhc8.86 mg/LMay 2026Health-study range17 samples210
Angola Crest Ii8.53 mg/LJun 2026a high point — runs lowerHealth-study range36 samples159
Carey Estates, Llc8.52 mg/LFeb 2026a high point — runs lowerHealth-study range25 samples312
Sussex Manor Mobile Home Park8.46 mg/LMar 2026Health-study range4 samples195
Seaford Water Department8.13 mg/LJun 2026a high point — runs lowerHealth-study range77 samples6,699
Largest systems
SystemMost recent resultBandBased onPeople served
Artesian Water Company7.70 mg/LApr 2026a high point — runs lowerHealth-study range75 samples231,114
Wilmington Water Department2.44 mg/LJun 2026Human impact likely71 samples107,976
Veolia Water Delaware, Inc2.75 mg/LApr 2026Human impact likely6 samples100,495
Rehoboth Pump District (Tui)3.24 mg/LJun 2026a high point — runs lowerHuman impact clear101 samples81,417
Bethany Bay Pump District0.05 mg/LJun 2026Natural background12 samples51,000

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 concentrate in Sussex County

Human impact is clear on drinking water served in all three of Delaware’s 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.

DE 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.New Castle County — 2 systems at 3.00–4.99 mg/L as N; 8 systems at 5.00 mg/L as N or aboveKent County — 2 systems at 3.00–4.99 mg/L as N; 3 systems at 5.00 mg/L as N or aboveSussex County — 25 systems at 3.00–4.99 mg/L as N; 23 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

Sussex leads this layer with 23 reporting systems, followed by New Castle, Kent. Higher results concentrate in Sussex County.

Counties with the most systems at or above 3 mg/L as N
County3–4.99≥5Total ≥3
Sussex252348
New Castle2810
Kent235

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 Delaware system

What the statewide pattern says

A shallow, oxygen-rich sand aquifer under poultry country

Delaware's higher nitrate is a Delmarva story: an oxic surficial sand aquifer under poultry and row crops, where nitrate persists to depth rather than breaking down.

The Delmarva Peninsula is underlain by the surficial (Columbia) aquifer: shallow, unconfined, and made of permeable, oxygen-rich sand. That combination makes it one of the more nitrate-vulnerable settings in the country, because the oxygen means nitrate is stable — it does not break down, it persists (Nolan and Hitt, 2006).

So elevated nitrate here is not just a surface skim. In the foundational Delmarva assessment, nitrate exceeded the federal limit in roughly a third of agricultural-area samples, and it reaches the base of the aquifer eighty to a hundred feet down (Ator and Denver, 2015; Denver, 1993). The dominant source is Delaware's poultry economy — chicken manure plus fertilizer — a Delmarva signature distinct from the Corn Belt or the dairy valleys of California.

Denitrification happens, but only locally — where groundwater passes through anoxic sediments near streams — and flow paths can bypass those zones (Bratton and others, 2004). The supported source reading is agricultural, poultry-manure-heavy — not a certified source at any individual system. Because the water moves slowly, surface changes take decades to register underground, and that same groundwater is the main route carrying nitrate onward to the Chesapeake and the Inland Bays (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 Delaware pattern does—and does not—say

Where does nitrate concentrate in Delaware community water systems?

Sussex leads this layer with 23 reporting systems, followed by New Castle, Kent. Higher results concentrate in Sussex County.

Does a deeper well mean lower nitrate in Delaware?

Less than elsewhere. The surficial aquifer is oxygen-rich to its base, so nitrate does not break down with depth the way it does in reducing aquifers; elevated nitrate has been measured eighty to a hundred feet down in agricultural areas. Depth helps less here than in most settings.

Can this page say the source is agriculture?

At the zone level, yes — carefully, and with a Delaware-specific reading: poultry manure plus fertilizer is the dominant nitrogen source on the peninsula. 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: 207 Delaware 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. 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 — roughly a third of agricultural-area samples exceeded the federal limit.
  5. Ator SW, Denver JM (2015). Understanding nutrients in the Chesapeake Bay watershed and implications for management and restoration — the Eastern Shore. USGS Circular 1406.
  6. Bratton JF, Bohlke JK, Manheim FT, Krantz DE (2004). Ground water beneath coastal bays of the Delmarva Peninsula: ages and nutrients. Ground Water 42(7):1021–1034.
  7. Cruz RM, and others (2024). Comparison of water quality in shallow groundwater near agricultural areas in the Delaware Coastal Plain, 2014 and 2019. USGS Scientific Investigations Report 2024-5076.