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Nevada water profile

Nitrate in Nevada community water systems

Among the quarter of Nevada systems with a current result here — 49 of 195 — one in five reads at or above 3.00 mg/L, on evidence that points at urban and septic nitrogen on desert basin-fill aquifers, with natural desert-soil nitrate in reserve. See the pattern and what each reporting system measured in the three years from August 9, 2023 to August 9, 2026.

Browse all 49 Nevada systems →

Search by the utility or system name shown on a water bill. Example: Las Vegas Valley Water District. Private wells are not in this inventory.

25%
of the state’s 195 active community water systems have a current result here
49
systems with a current nitrate result
2,925,399
people served by those reporting systems
18.4%
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 Nevada's systems fall across the five bands

Most systems report below 3 mg/L

Natural background
0.00–0.99 mg/L as N
17 systems · 759,543 served
Human impact likely
1.00–2.99 mg/L as N
16 systems · 50,252 served
Human impact clear
3.00–4.99 mg/L as N
7 systems · 28,373 served
Health-study range
5.00–9.99 mg/L as N
9 systems · 2,087,231 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 9 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 Oct 2025; the typical system was last tested around Oct 2024. 48 systems sampled their own water; 1 system carries 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
Star City Properties8.20 mg/La high point — runs lowerHealth-study rangeCCR summary, unverified285
Elko City Of7.63 mg/La high point — runs lowerHealth-study rangeCCR summary, unverified23,000
Truckee Meadows Water Authority7.60 mg/La high point — runs lowerHealth-study rangeCCR summary, unverified442,000
Sun Valley Gid7.60 mg/La high point — runs lowerHealth-study rangeCCR summary, unverified17,000
Great Basin Water Co Spanish Springs7.60 mg/La high point — runs lowerHealth-study rangeCCR summary, unverified1,460
Tonopah Public Utilities5.60 mg/LJan 2024Health-study rangeCCR summary, unverified2,853
Las Vegas Valley Water District5.30 mg/La high point — runs lowerHealth-study rangeCCR summary, unverified1,539,277
Signature Towers5.30 mg/La high point — runs lowerHealth-study rangeinherited from supplier2,356
Largest systems
SystemMost recent resultBandBased onPeople served
Las Vegas Valley Water District5.30 mg/La high point — runs lowerHealth-study rangeCCR summary, unverified1,539,277
Truckee Meadows Water Authority7.60 mg/La high point — runs lowerHealth-study rangeCCR summary, unverified442,000
North Las Vegas Utilities0.63 mg/LNatural backgroundCCR summary, unverified376,515
Henderson City Of0.68 mg/LNatural backgroundCCR summary, unverified336,534
Carson City Public Works5.02 mg/La high point — runs lowerHealth-study rangeCCR summary, unverified59,000

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

Basin-fill valleys carry the signal

Human impact is clear on drinking water served in five of Nevada’s 17 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.

NV 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.Washoe County — 0 systems at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveDouglas County — 2 systems at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveClark County — 1 system at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveWhite Pine County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveElko County — 0 systems at 3.00–4.99 mg/L as N; 1 system 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

Clark leads this layer with 1 reporting system, followed by Elko, Washoe. Basin-fill valleys carry the signal. Coverage note: the map places 53% of Nevada’s reporting systems. Of the rest, 1 carry a supplier’s result measured elsewhere and belong off this map; 22 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
Clark112
Douglas202
Elko011
Washoe011
White Pine101

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 53% of Nevada’s reporting systems. Of the rest, 1 carry a supplier’s result measured elsewhere and belong off this map; 22 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 Nevada system

What the statewide pattern says

Urban nitrogen, septic growth, and nitrate the desert stored away

Nevada's elevated systems sit in its populated basin-fill valleys — Las Vegas, Carson and Truckee — where USGS has documented shallow-aquifer nitrate from lawns, effluent, sewers and septic tanks, plus a natural reserve of desert-soil nitrate that irrigation can flush downward.

Nevada's reporting inventory is small — about 50 systems, a quarter of the state's — but one in five of those reports nitrate at or above 3.00 mg/L; whether the unreported three-quarters would hold that share, these records cannot say. The map covers Clark (Las Vegas), Douglas (Carson Valley), Washoe (Reno–Sparks), Elko and White Pine counties; the county file attributes only part of the inventory, and the coverage note beside the map says so.

Las Vegas Valley is the best-documented case. USGS found a median of 4.6 mg/L in 32 shallow monitoring wells, with 12 percent of samples above the 10 mg/L federal limit; an earlier valley study averaged 13 mg/L in wells under 100 feet deep against 3.2 mg/L in deeper ones. Sources named: lawn fertilizer, irrigation with treated effluent, leaking sewers and septic systems — and naturally occurring nitrate accumulated over thousands of years in desert soils, which excess irrigation can flush to the water table (USGS Professional Paper 1781). Deep public-supply wells in the valley mediate the risk: their median runs 0.65 mg/L.

Carson Valley in Douglas County shows the trend line. A 16-year USGS study found nitrate rising in 56 percent of long-term monitoring wells, with the highest values directly under dense septic-tank parcels — not under farmland — and groundwater ages of 30 to 40 years meaning the trend persists for decades (USGS WRIR 03-4152). Modeling projected concentrations would keep climbing toward the MCL in septic-dense subdivisions (USGS SIR 2013-5136), and a 2024 update found significant increases in 9 of 14 wells, with Johnson Lane and Gardnerville Ranchos samples having exceeded the MCL (USGS OFR 2024-1045).

The supported source reading is urban and septic nitrogen on basin-fill aquifers, with natural desert-soil nitrate contributing — 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 Nevada pattern does—and does not—say

Where does nitrate concentrate in Nevada community water systems?

Clark leads this layer with 1 reporting system, followed by Elko, Washoe. Basin-fill valleys carry the signal.

Why do so many of Nevada's reporting systems show nitrate?

Among the systems reporting here, three stacked reasons: its cities sit on shallow basin-fill aquifers; those valleys concentrate septic systems, effluent irrigation and lawn fertilizer; and desert soils store natural nitrate that irrigation can flush downward. Deep supply wells mostly avoid it — Las Vegas Valley's deep public wells median 0.65 mg/L — but shallow and mid-depth systems answer.

Should a Nevada private well be tested for nitrate?

Yes, especially in Carson Valley and the Las Vegas and Truckee basins, where USGS has measured rising nitrate under septic-dense neighborhoods and shallow-aquifer medians near 4.6 mg/L. Nevada wells can also carry arsenic and uranium, arguing for a broad certified-lab panel rather than nitrate alone.

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: 49 Nevada 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 (2012). Conceptual Understanding and Groundwater Quality of Selected Basin-Fill Aquifers in the Southwestern United States. Professional Paper 1781 — Las Vegas Valley shallow aquifer nitrate median 4.6 mg/L, 12% of samples >10 mg/L; natural desert-soil nitrate flushed by irrigation (Walvoord and others, 2003).
  5. Rosen MR (2003). Trends in Nitrate and Dissolved-Solids Concentrations in Ground Water, Carson Valley, Douglas County, Nevada, 1985–2001. USGS WRIR 03-4152 — nitrate rising in 56% of long-term wells; highest values under septic-dense parcels.
  6. USGS (2013). The Distribution and Modeling of Nitrate Transport in the Carson Valley Alluvial Aquifer. SIR 2013-5136 — projections to 2059 show concentrations approaching or exceeding the MCL in septic-dependent subdivisions.
  7. Naranjo RC, and others (2024). Assessment of Water Levels, Nitrate, and Arsenic in the Carson Valley Alluvial Aquifer. USGS OFR 2024-1045 — significant nitrate increases in 9 of 14 wells; MCL exceeded in Johnson Lane and Gardnerville Ranchos samples.