Well water in Yuma County, Arizona

1in2

Testing strongly recommended

tested well samples in Yuma County exceeded the EPA limit for arsenic (10 ug/L), based on public data from USGS Water Quality Portal.

7,536 test results across 14 contaminants from at least 782 wells, 1929 to 2026; chloride has the most at 2,418. Data refreshed September 15, 2026.

Compiled by Nick at Well Water Nerd from public records. How these pages are built

An estimated 9,940 people in Yuma County get their drinking water from a private well, per USGS 2015 county water use. That is about 5% of residents.

Separately, the USGS national arsenic model estimates that 19% of the 9,940 people on private wells in Yuma County draw water above 10 ug/L (the model's range is 16% to 22%), from geology and well depth rather than local tests.

What individual samples found

Each row summarizes every public sample for that contaminant inside Yuma County. Above limit means above the EPA maximum contaminant level; where EPA has no enforceable limit, the row shows a health guideline or nuisance level instead.

Contaminant	Above limit	Samples	Detected	Median	Highest	Limit
Arsenic 1980 to 2026	43%	277	72%	6	176	10 ug/L EPA limit
Fluoride 1945 to 2026	14%	945	99%	0.77	10	4 mg/L EPA limit
Nitrate 1946 to 2026	12%	673	75%	0.7	186	10 mg/L EPA limit
Uranium 2005 to 2026	5%	20	100%	6.09	38	30 ug/L EPA limit
Lead 1980 to 2026	<1%	252	9%	0	18	15 ug/L EPA limit
Copper 1980 to 2026	0%	257	33%	0	0.041	1.3 mg/L EPA limit
Radium (226 + 228) 1995 to 2026	0%	22	59%	0.108	3.7	5 pCi/L EPA limit
Chloride 1929 to 2026	no limit	2,418	100%	655	12,000	250 mg/L nuisance level
Sodium 1954 to 2026	no limit	1,713	100%	645	12,000	20 mg/L health guideline
Iron 1951 to 2026	no limit	484	63%	13.3	6,250	300 ug/L nuisance level
Manganese 1972 to 2026	no limit	444	67%	71.5	7,100	300 ug/L health guideline
Radon 2013 to 2016	no limit	20	95%	344	2,150	2,000 pCi/L health guideline

Sampled fewer than 10 times, too few to summarize: PFOA (9), E. coli (2).

Over time

Share of samples above the limit by period. A cell needs ten samples to show; a comparison needs twenty in each period. Later periods sample fewer wells, and often the ones already known to have a problem.

Contaminant	before 2000	2000s	2010s	2020s
Fluoride	13%777 samples	18%33 samples	28%85 samples	2%50 samples
Nitrate	12%445 samples	18%73 samples	10%49 samples	5%106 samples
Arsenic	34%150 samples	34%35 samples	61%85 samples	n/a
Copper	0%145 samples	0%20 samples	0%85 samples	n/a
Lead	1%140 samples	0%20 samples	0%85 samples	n/a

Fluoride above the limit in Yuma County fell from 28% of 85 samples in the 2010s to 2% of 50 in the 2020s.

Nitrate above the limit in Yuma County fell from 10% of 49 samples in the 2010s to 5% of 106 in the 2020s.

Arsenic above the limit in Yuma County rose from 34% of 35 samples in the 2000s to 61% of 85 in the 2010s.

Copper, lead have held within a few points between the two most recent periods with enough samples.

Closer than the county

See the sampled wells near your address

The same records, drawn around one point: which wells within a few miles were sampled and what they found, how deep the wells next to you were drilled, and any leaking tank or cleanup site within a mile.

Check my address

What this means

The contaminants most often above their limit here are arsenic (43% of 277 samples), fluoride (14% of 945 samples), and nitrate (12% of 673 samples). A well next door can differ sharply from yours because bedrock fractures, well depth and plumbing all matter, so these rates describe the area, not your tap.

Chloride, Iron, and Manganese are widespread in local groundwater. They are mainly a staining and taste problem, but high manganese also carries a health advisory for infants.

What to test for in Yuma County

1
Arsenic
43% of 277 local samples were above the limit.
2
Fluoride
14% of 945 local samples were above the limit.
3
Nitrate
12% of 673 local samples were above the limit.
4
Uranium
5% of 20 local samples were above the limit.
5
Lead
<1% of 252 local samples were above the limit.
6
Coliform bacteria
Recommended for every private well, every year.
7
Radon
Median local reading is 344 pCi/L.
8
Volatile organic compounds (VOCs)
174 leaking underground storage tank sites on record locally.

Test your Yuma County well for arsenic, fluoride and nitrate

Certified lab analysis of your own tap water, bottles and prepaid return shipping included. The Essential well panel covers arsenic, uranium, nitrate, lead, copper, manganese, iron, sodium and bacteria; radon and PFAS are add-ons.

Order the Tap Score well water test kit, from $209 Already tested? Upload the report

Just want bacteria checked first? Tap Score coliform and E. coli test, $99. Coliform and E. coli are the tests every well needs every year.

Want a quick look before paying for a lab? Home well water test strips on Amazon check hardness, iron, pH and nitrate in minutes. They are a screen, not a result: arsenic, bacteria, uranium and PFAS need a certified lab.

Affiliate links: the merchant pays us a commission and the price is the same for you. It does not change what the data above says. As an Amazon Associate we earn from qualifying purchases.

Where to get a well tested in Arizona: certified labs, state programs and prices.

Already have results back? Get your lab report read against the Yuma County numbers, $29. Every line explained, ranked by what matters, with the fix for each.

Wells in Yuma County

4,895 domestic wells in Yuma County are on record with the state since 1970. the typical well is 185 feet deep (one in ten goes past 243 feet).

In a typical Yuma County well, the median yield is 25 gallons per minute, <1% of wells yield under 3 gallons per minute and usually need a storage tank.

446

1970s

550

1980s

772

1990s

641

2000s

153

2010s

109

2020s

Find your own well's report

The state keeps the driller's report for most wells drilled since 1984. It tells you how deep your well is, where bedrock starts, and how much water it makes, which decides what treatment can work.

Open ADWR Wells55 registry and choose Water Well.
The record lists depth, water level, casing depth and the tested rate, plus a link to the drilling log.

Arizona has registered wells since 1980; earlier wells often have no record.

The rock under Yuma County

Basin and Range basin-fill aquifers

Unconsolidated sand and gravel. Wells in sand and gravel are usually shallow and productive, and they recharge quickly from the surface. That makes them the most exposed to nitrate, bacteria and anything spilled nearby, and the least likely to carry arsenic or radon from the rock.

Classification from the USGS Principal Aquifers of the United States (national map, 2003 edition, GIS release 2015), read at the county centroid. A single well can sit in a different unit, especially near a boundary.

Official help in Arizona

Two places to start that are not selling anything: the state program that answers private well questions, and its list of labs certified to run drinking water tests. A certified lab is the difference between a result you can act on and a number.

Well Water, ADHS
Licensed Commercial Drinking Water Laboratories, ADHS

Contamination sources on record in Yuma County

ADEQ records 174 leaking underground storage tank sites in Yuma County, among 176 regulated sites in total. Groundwater does not follow property lines, so a well within a few hundred feet of one of these is worth testing for what that site could release.

174: leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
2: lined landfills and transfer facilities

Treatment that fits the local profile

Arsenic

Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange

Fluoride

Point-of-use reverse osmosis; Activated alumina; Distillation

Nitrate

Point-of-use reverse osmosis; Anion exchange; Distillation

Uranium

Point-of-use reverse osmosis; Anion exchange; Whole-house anion exchange

Lead

Point-of-use reverse osmosis; Certified lead-removal carbon filter; Neutralizing filter to raise pH and stop leaching

Systems we would look at first

Some links below are affiliate links. If you buy through one, the merchant pays us a commission at no extra cost to you. It does not change which products we list or what the data says.

For arsenic

Under-sink reverse osmosis system

under-sink or countertop, about $300

Look for NSF/ANSI 58 certification listing the contaminant you need removed.

For arsenic

Whole-house arsenic and uranium filter

whole-house, at the point of entry, about $2,500

Adsorptive iron-based media; sized to your well yield.

For arsenic

Aquasana SmartFlow reverse osmosis

under-sink or countertop, about $225

Certified to NSF/ANSI 58 and 53 to reduce arsenic (96%, pentavalent), fluoride (90%), lead (99%), nitrate, nitrite and PFOA/PFOS at the kitchen tap, with a remineralizer.

For lead

Aquasana Claryum 3-Stage under-sink filter

under-sink or countertop, about $175

Certified to NSF/ANSI 53 to reduce 99% of lead and 99.7% of PFOA and PFOS at the tap. Not a fix for arsenic, nitrate or bacteria.

For lead

Acid neutralizing filter

whole-house, at the point of entry, about $1,200

Raises pH so plumbing stops leaching lead and copper.

Free, no obligation

Get on the list for a free in-home water test in Yuma County

No water treatment company serves Yuma County through Well Water Nerd yet. We are signing licensed companies on county by county: they test at your tap for free, walk you through the numbers, and quote treatment only if something needs fixing. Leave your details and you are first in line. Nothing is shared until a company joins for Yuma County, and you get an email naming it first.

Common questions

How deep are wells in Yuma County?

The typical domestic well in Yuma County is 185 feet deep, based on 4,895 wells reported to the state since 1970. One in ten is deeper than 243 feet.

Is there arsenic in well water in Yuma County?

Arsenic was detected in 72% of 277 public well samples in Yuma County, and 43% were above the EPA limit of 10 ug/L. Arsenic has no taste or smell; a lab test is the only way to know your level.

How high is radon in well water in Yuma County?

The median radon level across 20 public samples in Yuma County was 344 pCi/L, with a high of 2,150 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.

How often should I test a private well in Yuma County?

Test for bacteria and nitrate every year. Test once for arsenic, uranium, radon, fluoride, manganese and PFAS, then again every three to five years or after any change in taste, color, or plumbing.

Counties near Yuma County

Closest first. Groundwater does not stop at a line on a map, so the next county over is a fair second opinion.

Want the numbers themselves? Download the Arizona dataset as CSV, every county and town, with the sources named.

Sources

USGS Water Quality Portal: 7,536 samples in Yuma County. Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators. Retrieved September 3, 2026.
USGS national arsenic model (Ayotte 2017): estimated share of 9,940 people on private wells in Yuma County above 10 ug/L of arsenic, from geology, well depth and land use. County estimates of domestic well users with arsenic above 10 ug/L from the USGS national logistic regression model (Ayotte, Medalie and Qi, 2017), with private well population from the USGS 2015 county water-use compilation (Dieter and others, 2018). Retrieved September 15, 2026.
Arizona ADWR well registry (Wells55): 11,043 well records in Yuma County, 4,895 domestic. Registered wells from the Arizona Department of Water Resources Wells55 registry. Only aggregates are shown; owner names and addresses are never stored. Retrieved September 18, 2026.
ADEQ regulated sites: 176 regulated sites located in Yuma County. Leaking underground storage tank sites and municipal landfills from the Arizona Department of Environmental Quality. Retrieved September 18, 2026.

Non-detects count as samples and are treated as zero when computing medians. Exactly at the limit counts as not above it. A sample belongs to the town containing the well's reported coordinates.