New Mexico well water by county: arsenic and nitrate
Modelled arsenic and nitrate for private-well users in every New Mexico county, what to test for, and where to find a certified lab. Private wells aren’t covered by the Safe Drinking Water Act.
All 33 counties
- Santa Fe CountyWell users 29,400Arsenic about 12 in 100Nitrate 0.7 mg/L
- Valencia CountyWell users 28,000Arsenic about 58 in 100Nitrate 1.8 mg/L
- Bernalillo CountyWell users 27,600Arsenic about 38 in 100Nitrate 0.9 mg/L
- Doña Ana CountyWell users 20,900Arsenic about 17 in 100Nitrate 0.7 mg/L
- Sandoval CountyWell users 16,400Arsenic about 38 in 100Nitrate 0.5 mg/L
- Rio Arriba CountyWell users 15,900Arsenic about 10 in 100Nitrate 0.8 mg/L
- Taos CountyWell users 15,200Arsenic about 8 in 100Nitrate 0.5 mg/L
- San Juan CountyWell users 11,200Arsenic about 8 in 100Nitrate 0.4 mg/L
- Lea CountyWell users 10,400Arsenic about 16 in 100Nitrate 5.3 mg/L
- McKinley CountyWell users 9,900Arsenic about 7 in 100Nitrate 0.1 mg/L
- Chaves CountyWell users 8,100Arsenic about 6 in 100Nitrate 2.8 mg/L
- Luna CountyWell users 8,000Arsenic about 15 in 100Nitrate 1.8 mg/L
- Torrance CountyWell users 7,600Arsenic about 13 in 100Nitrate 1.4 mg/L
- Grant CountyWell users 7,600Arsenic about 12 in 100Nitrate 1.0 mg/L
- Otero CountyWell users 7,400Arsenic about 5 in 100Nitrate 1.4 mg/L
- San Miguel CountyWell users 5,900Arsenic about 4 in 100Nitrate 0.5 mg/L
- Curry CountyWell users 5,600Arsenic about 21 in 100Nitrate 3.9 mg/L
- Roosevelt CountyWell users 4,100Arsenic about 30 in 100Nitrate 7.1 mg/L
- Lincoln CountyWell users 4,000Arsenic about 3 in 100Nitrate 0.5 mg/L
- Cibola CountyWell users 3,900Arsenic about 10 in 100Nitrate 0.2 mg/L
- Socorro CountyWell users 3,900Arsenic about 20 in 100Nitrate 0.9 mg/L
- Eddy CountyWell users 3,500Arsenic about 7 in 100Nitrate 2.4 mg/L
- Sierra CountyWell users 2,800Arsenic about 11 in 100Nitrate 0.8 mg/L
- Catron CountyWell users 2,400Arsenic about 12 in 100Nitrate 0.2 mg/L
- Mora CountyWell users 1,800Arsenic about 3 in 100Nitrate 0.5 mg/L
- Union CountyWell users 1,800Arsenic about 5 in 100Nitrate 1.1 mg/L
- Hidalgo CountyWell users 1,500Arsenic about 10 in 100Nitrate 1.3 mg/L
- Colfax CountyWell users 1,400Arsenic about 3 in 100Nitrate 0.5 mg/L
- Quay CountyWell users 1,400Arsenic about 7 in 100Nitrate 3.9 mg/L
- Guadalupe CountyWell users 880Arsenic about 6 in 100Nitrate 1.9 mg/L
- De Baca CountyWell users 520Arsenic about 16 in 100Nitrate 3.3 mg/L
- Harding CountyWell users 330Arsenic about 5 in 100Nitrate 1.8 mg/L
- Los Alamos CountyWell users 100Arsenic about 4 in 100Nitrate 0.1 mg/L
Each mark = 1 in 100 well users the model places above 10 µg/L arsenic (scale 0–10)10 mg/L nitrate: the federal limit (MCL) for public systems
- These figures describe the area, not your well. Only a lab test shows what’s in your water.
- CDC says the Well Water Index figures “do not describe risk to individual wells.” (CDC Tracking Network)
- The arsenic model is better at spotting low-arsenic areas than at confirming high ones.
- Well-user counts are 2010 USGS estimates; tract values are averages over each census tract.
- Total coliform bacteriaEvery year
- NitrateEvery year
- Total dissolved solidsEvery year
- pHEvery year
- ArsenicAsk your local health department
EPA: Private Drinking Water Wells · CDC: Guidelines for Testing Well Water
Use a state-certified lab
New Mexico Environment Department, Drinking Water Bureau lists the laboratories certified to test drinking water in New Mexico.
Screening tells you if something is worth a closer look
A lab result is the number you can act on.
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Lab-certified results
ETR Labs Basic Water Quality Test Kit
ETR Laboratories
50+ substances, including lead, copper, arsenic, nitrate, hardness and coliform bacteria
- Analyzed by Environmental Testing and Research Laboratories (ETR Labs), Leominster, MA · ISO/IEC 17025:2017, ANAB certificate AT-2638
- Turnaround: 2–4 business days after the lab receives it
What it can't tell you: It does not test PFAS, and not every result on the panel falls under the lab's accredited scope.
Screening: quick check, not lab-grade
Watersafe Drinking Water Test Kit
Silver Lake Research
Lead, bacteria, nitrate, copper, iron, chlorine, hardness and pH
- Turnaround: Minutes; the bacteria test can take up to 48 hours
What it can't tell you: Each test gives a yes/no or a rough range, not a lab number, and it cannot detect PFAS or arsenic.
A mail-in kit’s lab is accredited (ISO/IEC 17025) but may not be certified by your state. For a home sale, a loan, or a health-department follow-up, use a state-certified lab.
New Mexico well water
Sources: CDC Well Water Index (2024) · USGS arsenic and nitrate models · USGS domestic well populations · EPA and CDC testing guidance. Data last updated 2026-10-08. All sources →
How many people use private wells in New Mexico?
About 269,400 people across 33 New Mexico counties, by the USGS 2010 estimate. USGS models place about 55,400 of them in areas where wells are likely to be above the 10 µg/L arsenic limit. These are area estimates, not well results.
Are private wells regulated in New Mexico?
The quality and safety of drinking water from private domestic wells are not regulated by the Federal Government under the Safe Drinking Water Act nor by most state governments and laws. (EPA) Testing and treatment are the owner's responsibility.
Where can I get my well tested in New Mexico?
New Mexico Environment Department, Drinking Water Bureau keeps the list of laboratories certified to test drinking water in New Mexico. Only use laboratories that are certified to do drinking water testing. (EPA)