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Kentucky water profile

Nitrate in Kentucky community water systems

Kentucky's community water systems mostly report nitrate below 3 mg/L — but Kentucky is karst country, and karst is the terrain where public-system data sees least. See the pattern and what each reporting system measured in the three years from August 9, 2023 to August 9, 2026.

Browse all 357 Kentucky systems →

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

96%
of the state’s 374 active community water systems have a current result here
357
systems with a current nitrate result
4,860,346
people served by those reporting systems
1.4%
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 Kentucky's systems fall across the five bands

Most systems report below 3 mg/L

Natural background
0.00–0.99 mg/L as N
265 systems · 3,070,746 served
Human impact likely
1.00–2.99 mg/L as N
79 systems · 1,756,569 served
Human impact clear
3.00–4.99 mg/L as N
8 systems · 24,689 served
Health-study range
5.00–9.99 mg/L as N
5 systems · 8,342 served
Above the federal limit
10.00 mg/L and above
0 systems · 0 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 5 systems reporting 5 mg/L or more, 1 stayed at or above 5 across the whole three-year range; the other 4 reached it only on a high sample and otherwise ran lower.

Most recent reading Jun 2026; the typical system was last tested around Feb 2026. 190 systems sampled their own water; 167 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
Warsaw Water Works6.51 mg/LMar 2026a high point — runs lowerHealth-study range11 samples1,988
Stella Trailer Park5.96 mg/LMay 2026Health-study range12 samples74
Graves Co Water Dist - Sedalia5.63 mg/LApr 2026Health-study range11 samples371
Gallatin County Water District5.61 mg/LMar 2026a high point — runs lowerHealth-study range14 samples5,860
Riverside 25 Llc5.28 mg/LApr 2026Health-study range10 samples49
Cadiz Municipal Water Co4.86 mg/LMay 2026a high point — runs lowerHuman impact clear3 samples6,165
Carrollton Utilities4.17 mg/LApr 2026Human impact clear3 samples6,851
West Carroll Water District - Milton4.09 mg/LMar 2026Human impact clearinherited from supplier86
Largest systems
SystemMost recent resultBandBased onPeople served
Louisville Water Company1.20 mg/LFeb 2026Human impact likely22 samples764,769
Kentucky-American Water Co0.59 mg/LApr 2026Natural background9 samples669,042
Northern Kentucky Water District0.91 mg/LJun 2025Natural background6 samples259,949
Warren County Water District1.36 mg/LJan 2026Human impact likelyinherited from supplier91,118
Hardin County Water District #22.60 mg/LApr 2026Human impact likely6 samples76,326

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

A thin signal on karst country

Human impact is clear on drinking water served in nine of Kentucky’s 120 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.

KY 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.Carroll County — 3 systems at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveGraves County — 0 systems at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveTrigg County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveCarlisle County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveGallatin County — 0 systems at 3.00–4.99 mg/L as N; 2 systems at 5.00 mg/L as N or aboveBoone County — 1 system at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveBallard County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveCalloway County — 0 systems at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveTrimble County — 1 system at 3.00–4.99 mg/L as N; 0 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

Gallatin leads this layer with 2 reporting systems, followed by Boone, Calloway, Graves. A thin signal on karst country.

Counties with the most systems at or above 3 mg/L as N
County3–4.99≥5Total ≥3
Carroll303
Boone112
Gallatin022
Ballard101
Calloway011

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 Kentucky system

What the statewide pattern says

Low public readings over fast limestone

Kentucky's public-system nitrate is low — but most of the state’s drinking-water terrain is karst, where sinkholes and sinking streams connect the surface to the aquifer in days and private wells carry the real exposure.

More than half of Kentucky is underlain by karst — the Inner Bluegrass, the Western Pennyroyal around Mammoth Cave, and the Eastern Pennyroyal — where rain and everything it carries can enter the aquifer through sinkholes and sinking streams with little filtration. Kentucky Geological Survey dye-tracing and conduit work, such as the Cane Run–Royal Spring basin that supplies part of Georgetown, documents how fast and how far that connection runs (Kentucky Geological Survey).

Nitrate follows it. A comparative study of karst systems found waters in the Mammoth Cave area carrying distinctly higher nitrate than a minimally impacted Kentucky karst valley, which ran 0.13–1.54 mg/L — with soil organic matter and mineralized fertilizer as the identified sources (Angel and Peterson, 2015).

Against that backdrop the public-system map is genuinely thin: the few higher readings scatter along the Ohio River corridor and the Jackson Purchase rather than over the classic karst. That is partly real — karst public systems often treat or blend — and partly a blind spot, because karst communities lean on private wells that no public-system database sees.

The supported source reading is soil, fertilizer and livestock nitrogen on karst terrain — not a certified source at any individual system, and in Kentucky a documented vulnerability more than a documented public-system pattern (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 Kentucky pattern does—and does not—say

Where does nitrate concentrate in Kentucky community water systems?

Gallatin leads this layer with 2 reporting systems, followed by Boone, Calloway, Graves. A thin signal on karst country.

Kentucky's public systems test low — why does karst still matter?

Karst determines how fast surface contamination reaches groundwater, and Kentucky is majority karst. Public systems in karst often treat or blend, and many karst residents drink from unregulated private wells — so a low public-system average can coexist with elevated private wells on the same limestone.

What does the Kentucky nitrate literature actually show?

Comparative karst work found the Mammoth Cave area carrying clearly higher nitrate than a minimally impacted Kentucky karst valley, sourced to soil organic matter and mineralized fertilizer. Kentucky Geological Survey dye-tracing shows the plumbing: sinkholes and sinking streams connect the surface to the aquifer directly.

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: 357 Kentucky 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. Angel JC, Peterson EW (2015). Nitrates in karst systems: comparing impacted systems to a relatively unimpacted system. Journal of Geography and Geology 7:65–76 — Mammoth Cave area karst waters higher in nitrate than an unimpacted Kentucky valley (0.13–1.54 mg/L).
  5. Kentucky Geological Survey, Water Resources Section. Karst groundwater research: Cane Run–Royal Spring conduit studies — quantitative tracing of karst conduit flow and contaminant flux.