New Mexico Water Hardness by County
Water in New Mexico has a median hardness of 207 mg/L as CaCO₃ — "very hard" on the USGS scale — based on 43,494 measurements at 9,362 monitoring stations. Eddy County has the state's hardest measured water (1400 mg/L); Los Alamos County the softest (56). Rank: #13 of the 50 states and D.C.
New Mexico water hardness map — what the numbers mean. Data verified 2026-07-22.
Of New Mexico's 32 measured counties, 19 very hard, 7 hard, 5 moderately hard, and 1 soft. The hardest are Eddy County (1400 mg/L), Chaves County (1300), and De Baca County (960). Los Alamos County is the softest at 56 mg/L (soft).
About 87% of New Mexico's roughly 2.1 million residents in counties with gate-passing hardness data live where tap water is hard or worse.
Statewide, New Mexico's median works out to 12.1 grains per gallon and ranks #13 of the 50 states and D.C. Across 43,494 measurements at 9,362 stations — 9,277 of them since 2000 — the middle 80% of readings fall between 60 and 1150 mg/L. The public record runs from 1900 to 2026.
See where New Mexico sits nationally on the national map, or what its number means on the hardness scale.
Download the New Mexico water hardness map (PNG) — Water hardness by county in New Mexico: 32 counties mapped from USGS/EPA data, statewide median 207 mg/L (very hard); darker counties have harder water.
By county
Water hardness by county
The table lists all 32 measured New Mexico counties, hardest first. Their medians span 1400 mg/L in Eddy County to 56 in Los Alamos County — a 25× range. 1 more New Mexico county lacks gate-passing data.
| County | Median | Band | Results | Sites | Newest |
|---|---|---|---|---|---|
| Eddy County | 1400 | Very hard | 5,086 | 496 | 2023 |
| Chaves County | 1300 | Very hard | 1,290 | 370 | 2023 |
| De Baca County | 960 | Very hard | 293 | 82 | 2015 |
| Guadalupe County | 790 | Very hard | 818 | 79 | 2021 |
| Otero County | 700 | Very hard | 928 | 393 | 2024 |
| Lincoln County | 550 | Very hard | 631 | 285 | 2021 |
| Union County | 383.5 | Very hard | 369 | 132 | 2006 |
| Cibola County | 360 | Very hard | 806 | 492 | 2020 |
| Roosevelt County | 324.5 | Very hard | 151 | 89 | 2023 |
| Quay County | 320 | Very hard | 1,678 | 51 | 2023 |
| Doña Ana County | 299 | Very hard | 2,673 | 807 | 2022 |
| Lea County | 260 | Very hard | 215 | 162 | 2023 |
| Mora County | 244 | Very hard | 187 | 35 | 2006 |
| Socorro County | 237 | Very hard | 4,192 | 572 | 2020 |
| Colfax County | 230 | Very hard | 1,305 | 103 | 2018 |
| Harding County | 230 | Very hard | 145 | 103 | 2007 |
| Curry County | 213 | Very hard | 91 | 74 | 2022 |
| Sierra County | 207 | Very hard | 582 | 198 | 2019 |
| San Juan County | 200 | Very hard | 6,260 | 675 | 2023 |
| Bernalillo County | 156 | Hard | 1,833 | 724 | 2023 |
| Valencia County | 140 | Hard | 419 | 134 | 2017 |
| McKinley County | 131 | Hard | 1,168 | 704 | 2021 |
| Santa Fe County | 128 | Hard | 2,528 | 364 | 2025 |
| San Miguel County | 122 | Hard | 1,378 | 137 | 2023 |
| Catron County | 120 | Hard | 752 | 237 | 2020 |
| Rio Arriba County | 120 | Hard | 1,209 | 203 | 2026 |
| Sandoval County | 119 | Moderately hard | 1,984 | 502 | 2026 |
| Grant County | 113 | Moderately hard | 1,202 | 247 | 2022 |
| Hidalgo County | 110 | Moderately hard | 236 | 172 | 2014 |
| Taos County | 107 | Moderately hard | 2,281 | 269 | 2023 |
| Luna County | 91 | Moderately hard | 192 | 162 | 2014 |
| Los Alamos County | 56 | Soft | 327 | 43 | 2005 |
ZIP codes
ZIP codes in New Mexico
The ZIP codes below are grouped by the New Mexico county they fall in. Each ZIP takes its county's measured median — shown in the group header — so this is a ZIP-to-county guide, not a separate reading for every ZIP. To check the water system serving a specific address, use the lookup.
Eddy County · 1400 mg/L · Very hard
88210†88220†88254†88255†88256†88263†88268
Chaves County · 1300 mg/L · Very hard
88201†88203†88230†88232†88250†88253†88339†
De Baca County · 960 mg/L · Very hard
88119†88134†88136†
Guadalupe County · 790 mg/L · Very hard
87724†88353†88417†88431†88435†
Otero County · 700 mg/L · Very hard
79837†88081†88310†8831188314†88317†88325†8833088337†88340†88342†88344†88347†88349†8835088352†88354†
Lincoln County · 550 mg/L · Very hard
88301†88312†88316†88318†88323†88324†88336†88338†88341†88343†8834588346†88348†88351†88355
Union County · 383.5 mg/L · Very hard
88410†88415†88418†88419†88422†88424†88436†
Cibola County · 360 mg/L · Very hard
87005†87007†87014†87020†87021†87026†87034†87038†87040†87049†87051†87315†87321†87357†
Roosevelt County · 324.5 mg/L · Very hard
88113†88115†88116†88118†88125†88126†8813088132†
Quay County · 320 mg/L · Very hard
88120†88121†88401†88411†88427†88430†88434
Doña Ana County · 299 mg/L · Very hard
8793687937†87940†879418800188002†880038800488005†88007†88008†88011†88012†88021†880248802788044†88046880478804888052†8806388072†
Lea County · 260 mg/L · Very hard
88114†88231†88240†88242†8824488252†88260†88262†88264†88265†88267†
Mora County · 244 mg/L · Very hard
87712†87713†87715†87722†87723†87732†87734†87735†8773687750†87752†87753†
Socorro County · 237 mg/L · Very hard
87006†87011†87028†87062†87801†87823†87825†8782887831†87832†
Colfax County · 230 mg/L · Very hard
8771087714†87718†8772887729†87740†87747†87749†88414†
Harding County · 230 mg/L · Very hard
87730†87733†87743†88426†
Curry County · 213 mg/L · Very hard
88101†8810388112†88124†88135†
Sierra County · 207 mg/L · Very hard
87901†87930†87931†87933†87935†87939†87942†87943†88042†
San Juan County · 200 mg/L · Very hard
87037†87364†8740187402†8741087413†8741587416†8741787418†87419†87420†87421†87455†87461†87499†
Bernalillo County · 156 mg/L · Hard
87008†8702287059†87068†8710187102871048710587106†87107871088710987110871118711287113871148711687117†87120†87121†8712287123†87151†
Valencia County · 140 mg/L · Hard
8700287023†87031†87042†87060†
McKinley County · 131 mg/L · Hard
86515†87045†8730187305†87310†87311†87312†87313†87316†87317†87319†87320†87322†87323†87325†87326†87327†87347†87365†87375†
Santa Fe County · 128 mg/L · Hard
87010†8701587056†87501†87505†87506†87507†8750887522†87535†87540†87567†
San Miguel County · 122 mg/L · Hard
87538†87552†87560†87562†87565†87569†87573†87583†87701†87711†87731†87742†87745†87746†88416†88421†88439†
Catron County · 120 mg/L · Hard
87820†87821†87824†8782787829†87830†88039†
Rio Arriba County · 120 mg/L · Hard
87012†87017†87029†87046†87064†87412†87510†87511†87515†87516†87518†87520†87521†87523†87527†87528†87530†87532†87537†87539†87548†87549†87551†87554†87566†87575†87577†87578†87581†87582†
Sandoval County · 119 mg/L · Moderately hard
8700187004†87013†87018†8702487025†87027†87041†87043†87044†87047†87048†87052†87053†87072†8708387124†8714487544†
Grant County · 113 mg/L · Moderately hard
88022†88023†88025†88026†88028†88034†88038†88041†88043†88049†88051†88053†88055†88061†88065†
Hidalgo County · 110 mg/L · Moderately hard
88009†88020†88040†8804588056†
Taos County · 107 mg/L · Moderately hard
87512†87513†8751487517†875198752487525†87529†87531†87543†87553†87556†87557†87558†8756487571†87579†87580†
Luna County · 91 mg/L · Moderately hard
88029†88030†
Los Alamos County · 56 mg/L · Soft
87547
† 305 ZIP codes are not served by a mapped community water system — most are private-well areas. See well water hardness.
Source
Groundwater vs surface water
New Mexico's groundwater measures harder than its surface water — 258 mg/L across 11,277 samples versus 196 across 31,853, about 1.3× harder. Wells draw from groundwater, so well owners in New Mexico tend to see the harder number — 258 mg/L, very hard. Groundwater readings there run 45 to 1080 mg/L across the middle 80% of samples. The comparison draws on 6,684 groundwater and 2,541 surface-water monitoring sites; 3,105 readings above 2,000 mg/L were logged but held out of the medians as outliers.
Groundwater (wells)
258 mg/L as CaCO₃ · 11,277 results at 6,684 stations.
Surface water (rivers, lakes)
196 mg/L as CaCO₃ · 31,853 results at 2,541 stations.
Groundwater measures about 1.3× harder than surface water here.
Chemistry
Water chemistry in New Mexico
Beyond the hardness number, New Mexico's water carries a fuller chemical signature — here is how its measured parameters compare to national benchmarks.
TDS
319 mg/L · n=8,768
319 mg/L — about 1.4× the national county median of 226, consistent with hard, mineral-rich water.
pH
8 pH · n=8,050
pH 8 — within the EPA secondary range of 6.5–8.5, on the alkaline side.
Alkalinity
137 mg/L as CaCO3 · n=9,109
137 mg/L — substantial buffering capacity, which resists pH swings.
Calcium : Magnesium
58 : 12 mg/L ≈ 4.83 : 1 · n=13,248
Calcium is about 75% of New Mexico's hardness (58 mg/L Ca to 12 mg/L Mg), a little more calcium-rich than the national ~68% calcium share.
Parameter medians may include a small share of quality-control samples; the hardness lane is fully QC-filtered.
Aquifers
Major aquifers under New Mexico
3 aquifer systems supply much of New Mexico's measured groundwater.
- Roswell Basin aquifer system — median 1000 mg/L across 471 samples at 353 sites: very hard.
- Pecos River Basin alluvial aquifer — median 315 mg/L across 19 samples at 15 sites: very hard.
- Colorado Plateaus aquifers — median 270 mg/L across 3,010 samples at 1,824 sites: very hard.
Together these systems account for 3,500 measured samples at 2,192 sites. Aquifer medians pool samples across a whole system and can mask local variation — see the national aquifer map for how these compare across states.
Trend
Hardness over time
New Mexico's decade median moved from 120 mg/L in the 1910s to 166 in the 2020s. Over the series, the decade median peaked at 610 mg/L in the 1920s and bottomed at 120 in the 1910s. Decade medians reflect where and what agencies sampled in each era, not just changes in the water itself.
Scale
Where New Mexico sits on the scale
On the USGS scale, New Mexico's 207 mg/L is very hard — 12.1 grains per gallon, well above the 180 mg/L very-hard cutoff — among the hardest water measured in the US.
At 207 mg/L (12.1 gpg), water-softener owners in New Mexico typically set their unit to this hardness — settings calculator.
Questions
Frequently asked questions
- Is New Mexico's water hard?
- New Mexico's median hardness is 207 mg/L as CaCO₃, "very hard" on the USGS scale and 1.48× the national county median of 140 mg/L. About 87% of residents in measured counties have hard-or-worse water.
- Which county in New Mexico has the hardest water?
- Eddy County, with a median of 1400 mg/L as CaCO₃ across 5,086 measurements.
- Is well water harder than city water in New Mexico?
- Groundwater measures harder here — about 1.3× the surface water — so wells tend to run harder (groundwater 258 vs surface water 196 mg/L).
- How do I find my exact hardness in New Mexico?
- Search your ZIP on the lookup tool, read your utility's Consumer Confidence Report, or test at home with a kit.
- Is New Mexico's water harder than the national average?
- Yes. New Mexico's median of 207 mg/L is 1.48× the national county median of 140 mg/L, and New Mexico ranks #13 of the 50 states and D.C.
Compare
States with similar hardness
Two states measure closest to New Mexico's 207 mg/L: Texas at 200 mg/L and Missouri at 196 mg/L. New Mexico measures harder than 76% of states. Browse the full ranking on the statistics page.
More: hardness scale · check your address · national statistics · the national map.
By Marko Visic, MPharm, BSc Physics. Source: USGS/EPA Water Quality Portal — 43,494 New Mexico measurements. Data last verified . Methodology.
Cite this page: “New Mexico Water Hardness by County.” Hard Water Map. Retrieved 2026-07-22, https://hardwatermap.com/water-hardness/new-mexico/