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Tennessee water profile

Nitrate in Tennessee community water systems

Tennessee's nitrate signal is a karst signal: the mapped systems gather on the Highland Rim's Mississippian limestone and in the shallow sands of the western Coastal Plain, exactly where the state's own science says sinkhole country drinks. See the pattern and what each reporting system measured in the three years from August 9, 2023 to August 9, 2026.

Browse all 435 Tennessee systems →

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

98%
of the state’s 446 active community water systems have a current result here
435
systems with a current nitrate result
7,053,675
people served by those reporting systems
0.7%
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 Tennessee's systems fall across the five bands

Most systems report below 3 mg/L

Natural background
0.00–0.99 mg/L as N
337 systems · 6,219,360 served
Human impact likely
1.00–2.99 mg/L as N
76 systems · 706,834 served
Human impact clear
3.00–4.99 mg/L as N
19 systems · 74,080 served
Health-study range
5.00–9.99 mg/L as N
3 systems · 53,401 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 3 systems reporting 5 mg/L or more, not one of them stayed there across its whole three-year range — each reached 5 only on a high sample and otherwise ran lower.

Most recent reading Jun 2026; the typical system was last tested around Jan 2026. 325 systems sampled their own water; 110 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
Greenbrier Water & Sewer Dept5.12 mg/LMay 2026Health-study rangeinherited from supplier9,230
Puryear Water System5.12 mg/LApr 2026a high point — runs lowerHealth-study range9 samples833
Springfield Water System5.12 mg/LMay 2026Health-study range11 samples43,338
Mason Hall Development Corp4.45 mg/LDec 2025Human impact clear3 samples211
Huntland Water System4.31 mg/LMay 2026Human impact clear3 samples1,755
Iron City Utility District4.26 mg/LMay 2026Human impact clearinherited from supplier729
St Joseph Water System4.26 mg/LMay 2026Human impact clear3 samples1,533
West Robertson Water Authority4.05 mg/LMay 2026a high point — runs lowerHuman impact clear12 samples5,915
Largest systems
SystemMost recent resultBandBased onPeople served
Metro Water Services0.00 mg/LMar 2026Natural background6 samples778,153
Knoxville Utilities Board - Kub0.47 mg/LJun 2026Natural background3 samples254,671
Clarksville Water Department0.37 mg/LOct 2025Natural background3 samples251,864
Consolidated U.D. Of Rutherford Co0.22 mg/LOct 2025Natural background2 samples221,871
Tennessee American Water0.32 mg/LJan 2026Natural background4 samples207,046

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

Highland Rim karst, plus a western sands scatter

Human impact is clear on drinking water served in twelve of Tennessee’s 95 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.

TN 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.Gibson County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveMadison County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveCrockett County — 2 systems at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveObion County — 2 systems at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveCarroll County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveHenry County — 0 systems at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveRobertson County — 1 system at 3.00–4.99 mg/L as N; 2 systems at 5.00 mg/L as N or aboveLawrence County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveFranklin County — 5 systems at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveDecatur County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveUnicoi County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveLincoln 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

Robertson leads this layer with 2 reporting systems, followed by Henry. Highland Rim karst, plus a western sands scatter. Coverage note: the map places 79% of Tennessee’s reporting systems. All 93 of the rest buy their water and carry their supplier’s result, which was measured at the supplier’s source — shading their own county would put the reading in the wrong place. They are counted in the figures above.

Counties with the most systems at or above 3 mg/L as N
County3–4.99≥5Total ≥3
Franklin505
Robertson123
Crockett202
Obion202
Carroll101

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 79% of Tennessee’s reporting systems. All 93 of the rest buy their water and carry their supplier’s result, which was measured at the supplier’s source — shading their own county would put the reading in the wrong place. They are counted in the figures above.

Find a specific Tennessee system

What the statewide pattern says

Ten thousand caves, and an aquifer that listens to the surface

Tennessee's elevated systems concentrate in Franklin and the southern Highland Rim counties on Mississippian carbonate karst — an aquifer USGS ties directly to sinkhole density — with a second scatter in West Tennessee's shallow Coastal Plain sands.

Tennessee's 20 mapped systems above the natural-background band cluster in two provinces: the Highland Rim, led by Franklin County with Lawrence and Lincoln beside it, and the western Coastal Plain — Crockett, Obion, Carroll and Gibson counties — with Robertson County on the northern rim continuing Kentucky's Pennyroyal karst.

The Highland Rim mechanism is documented. The Mississippian carbonates beneath it — Fort Payne, Warsaw, St. Louis limestones — form the state's most extensive karst aquifer, under a chert regolith riddled with solution openings that transmit surface water rapidly (USGS Professional Paper 813-L). Tennessee counts more than 10,000 documented caves, over 20 percent of the national total, mostly in these provinces (USGS Karst Interest Group, 2021).

The nitrate link is measured, not inferred: a USGS evaluation found areas of high and medium sinkhole density carry higher nitrate and pesticide concentrations than low-density areas (Lindsey and others, 2009, cited in the Karst Interest Group proceedings above). The fit to the map is direct — the same proceedings name Franklin, Lawrence, Lincoln and Montgomery as the counties where public systems pump the Mississippian aquifer hardest, over 2 million gallons a day each.

West Tennessee's scatter reads differently: shallow sands of the Mississippi embayment under row crop, where the protected Memphis aquifer supplies the cities but small shallow systems answer to the surface. The supported source reading is karst limestone conduit flow on the Highland Rim; shallow Coastal Plain sands in the west — 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 Tennessee pattern does—and does not—say

Where does nitrate concentrate in Tennessee community water systems?

Robertson leads this layer with 2 reporting systems, followed by Henry. Highland Rim karst, plus a western sands scatter.

Why does Franklin County, Tennessee, stand out on this map?

It sits squarely on the Highland Rim's Mississippian limestone — the state's most extensive karst aquifer — and USGS names it among the four counties where public systems pump that aquifer hardest. Karst moves surface nitrogen underground through sinkholes and solution openings with little filtering, and USGS has measured higher nitrate where sinkhole density is high.

Should a Tennessee private well be tested for nitrate?

Yes, especially on the Highland Rim and in karst areas with sinkholes, sinking streams or thin soils — and in West Tennessee's shallow sand country. Karst wells can change within days of a storm, so repeat testing across seasons tells the truer story.

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: 435 Tennessee 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 (2021). Karst Interest Group Proceedings, Tennessee karst chapters. SIR 2020-5019 — 10,000+ documented caves; Mississippian carbonates supply 17 Mgal/d to public systems (~218,000 people); Franklin, Lawrence, Lincoln, Montgomery named as heaviest users; areas of high sinkhole density carry higher nitrate and pesticides (Lindsey and others, 2009).
  5. USGS (1979). Summary Appraisals of the Nation's Ground-Water Resources — Tennessee Region. Professional Paper 813-L — Highland Rim Mississippian carbonates (Fort Payne, Warsaw, St. Louis) the region's most extensive aquifer; chert regolith and solution openings transmit water rapidly.