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Indiana water profile

Nitrate in Indiana community water systems

Indiana sends most of its farm nitrate to surface water through tile drains, keeping groundwater moderate — with higher pockets where sandy or carbonate aquifers lie shallow under farmland. See where higher public-system results sit and what each reporting system measured in the three years from August 9, 2023 to August 9, 2026.

Browse all 745 Indiana systems →

Search by the utility or system name shown on a water bill. Example: Citizens Energy Group. Private wells are not in this inventory.

97%
of the state’s 770 active community water systems have a current result here
745
systems with a current nitrate result
5,177,315
people served by those reporting systems
3.1%
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 Indiana's systems fall across the five bands

Most systems report below 3 mg/L

Natural background
0.00–0.99 mg/L as N
563 systems · 3,984,235 served
Human impact likely
1.00–2.99 mg/L as N
119 systems · 810,584 served
Human impact clear
3.00–4.99 mg/L as N
40 systems · 285,040 served
Health-study range
5.00–9.99 mg/L as N
22 systems · 96,434 served
Above the federal limit
10.00 mg/L and above
1 system · 1,022 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 23 systems reporting 5 mg/L or more, 9 stayed at or above 5 across the whole three-year range; the other 14 reached it only on a high sample and otherwise ran lower.

Most recent reading Jul 2026; the typical system was last tested around Dec 2025. 607 systems sampled their own water; 138 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
Montezuma Municipal Utility14.40 mg/LApr 2026Above the federal limit11 samples1,022
Bloomingdale Water Works8.24 mg/LApr 2026Health-study range11 samples562
Marshall Water Works8.24 mg/LApr 2026Health-study rangeinherited from supplier330
Owensville Water Works8.22 mg/LApr 2026Health-study range34 samples2,148
Ellis Water Company, Inc.7.72 mg/LJun 2026a high point — runs lowerHealth-study rangeinherited from supplier2,892
Linton Municipal Water Utility7.72 mg/LJun 2026a high point — runs lowerHealth-study range7 samples7,430
Switz City Water Works7.72 mg/LJun 2026a high point — runs lowerHealth-study rangeinherited from supplier888
Dugger Utilities7.72 mg/LJun 2026a high point — runs lowerHealth-study rangeinherited from supplier1,935
Largest systems
SystemMost recent resultBandBased onPeople served
Citizens Water - Indianapolis0.05 mg/LJul 2025Natural background56 samples880,345
Fort Wayne - 3 Rivers Filtration Plant0.52 mg/LJun 2026Natural background36 samples269,994
Indiana American Water - Northwest0.35 mg/LApr 2026Natural background6 samples210,510
Evansville Water Utility0.99 mg/LJan 2026Natural background3 samples182,444
South Bend Water Works0.50 mg/LApr 2026Natural background98 samples115,000

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 sit in shallow-aquifer pockets, led by the southwest

Human impact is clear on drinking water served in 32 of Indiana’s 92 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.

IN 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.Johnson County — 3 systems at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveWayne County — 3 systems at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveMiami County — 1 system at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveFranklin County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveGreene County — 1 system at 3.00–4.99 mg/L as N; 4 systems at 5.00 mg/L as N or abovePosey County — 1 system at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveParke County — 0 systems at 3.00–4.99 mg/L as N; 4 systems at 5.00 mg/L as N or aboveOhio County — 2 systems at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or abovePerry County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveKnox County — 4 systems at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveElkhart County — 1 system at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveSullivan County — 0 systems at 3.00–4.99 mg/L as N; 2 systems at 5.00 mg/L as N or aboveTippecanoe County — 0 systems at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveKosciusko County — 1 system at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveMartin County — 2 systems at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveJackson County — 1 system at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveBrown County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveGibson County — 0 systems at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveVigo County — 3 systems at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveSwitzerland County — 1 system at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveJefferson County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveHamilton County — 1 system at 3.00–4.99 mg/L as N; 0 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 aboveMontgomery County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveMorgan County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveHarrison County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveVermillion County — 4 systems at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveSt. Joseph County — 0 systems at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveDearborn County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveBartholomew County — 2 systems at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveLaPorte County — 0 systems at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveUnion 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

Greene leads this layer with 4 reporting systems, followed by Parke, Sullivan, Elkhart. Higher results sit in shallow-aquifer pockets, led by the southwest.

Counties with the most systems at or above 3 mg/L as N
County3–4.99≥5Total ≥3
Greene145
Knox415
Parke044
Vermillion404
Johnson303

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 Indiana system

What the statewide pattern says

A tile-drainage state with shallow-aquifer pockets

Most of Indiana is glaciated and heavily tile-drained, so farm nitrate travels to the rivers while groundwater stays moderate — except where sandy outwash or shallow carbonate lies under farmland.

Most of Indiana is glaciated and heavily tile-drained, so agricultural nitrate travels to the rivers while groundwater stays moderate across much of the state — part of the Corn Belt nitrogen the Mississippi-basin SPARROW model tracks downstream (Robertson and Saad, 2021).

The higher-risk groundwater is where the ground is permeable and shallow: the sandy, gravelly glacial outwash along the Wabash, White, and Kankakee river systems, the surficial sands of the Kankakee region in the north, and the shallow carbonate bedrock of west-central and northeastern Indiana — the Midwestern Basins and Arches country it shares with western Ohio (Nolan and Hitt, 2006). The map fits: the higher-band systems gather in the southwestern Wabash-valley counties — Greene, Knox, Parke and Vermillion — where outwash and shallow bedrock sit under row crops.

The supported source reading is agricultural — row-crop nitrogen reaching permeable shallow aquifers — not a certified source at any individual system. The same slow travel times apply: the water reflects past land use (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 Indiana pattern does—and does not—say

Where does nitrate concentrate in Indiana community water systems?

Greene leads this layer with 4 reporting systems, followed by Parke, Sullivan, Elkhart. Higher results sit in shallow-aquifer pockets, led by the southwest.

Where is Indiana groundwater nitrate highest?

In shallow, permeable settings under farmland: sandy outwash along the Wabash, White, and Kankakee systems, the northern Kankakee sands, and shallow carbonate bedrock in west-central and northeastern Indiana. The fine-till, tile-drained uplands send their nitrate to rivers instead and keep wells moderate.

Can this page say the source is agriculture?

At the zone level, yes — carefully: row-crop nitrogen reaching permeable shallow aquifers. 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: 745 Indiana 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. Robertson DM, Saad DA (2021). SPARROW Mississippi/Atchafalaya nutrient model. JAWRA 57(3) — the Corn Belt surface-water nitrogen pathway.