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Union County, New Mexico
Shrink-swell clay limits houses without basements on 28% of Union County's mapped land, a higher share than 79% of US counties and the 7th highest of 33 New Mexico counties. A shallow water table limits basements on 1%.
92.3% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list no flood losses here since 2016. 68% of homes were built before 1980, against 50% nationally; the median home dates from 1961.
Data as of October 13, 2026 · sources
expansive clay: shrink-swell limits slab homes
high water table: limits basements
in drought, October 13, 2026
of homes built before 1980
Soil under Union County
| Expansive clay (limits slab homes) | 28.4% |
| High water table (limits basements) | 1.2% |
| Septic fields very limited | 71.0% |
| Clay swell (LEP, by area) | 4.1% |
| High-swell land (LEP 6%+) | 20.6% |
| Mapped soil | 2,423,423 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Travessilla | 11% | n/a |
| Gruver | 9% | n/a |
| Spurlock | 9% | n/a |
| Dallam | 7% | n/a |
| Torreon | 6% | n/a |
| La Brier | 4% | n/a |
How we count · survey areas NM059 (2025-09-09)
What the numbers mean here
Clay swell averages a linear extensibility of 4.1% by land area here, and 21% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 28% of the mapped land.
Clay shrinks as it dries: 92.3% of the county is in drought on the latest map, and 28% of Union County's mapped land has shrink-swell clay.
Rain over the 12 months to August 2026: 10.91 in, 5.26 in below the 1991-2020 average year of 16.17 in.
USDA rates 71% of the land very limited for septic absorption fields.
Drought
92.3% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 34 of the last 52 weeks; the most was 100% of its area, in 29 weeks, most recently on the September 29, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 100% |
| D1 moderate drought or worse | 92.3% |
| D2 severe or worse | 70.1% |
| D3 extreme or worse | 25.8% |
| D4 exceptional | 0% |
Flood losses since 2016
FEMA's flood data list no flood losses in Union County since 2016.
Rain
| Average year, 1991-2020 | 16.17 in |
| 12 months to August 2026 | 10.91 in (-5.26) |
| 2025 | 16.99 in (+0.82) |
| Wettest year since 1895 | 1941: 34.49 in |
| Driest year since 1895 | 1934: 8.46 in |
| Days with 1 inch or more, normal at GRENVILLE (11 mi away) | 3 |
Homes
| Housing units | 2,101 |
| Median year built | 1961 |
| Built before 1980 | 68% |
| Built 2000 or later | 10% |
| Owner-occupied | 72% |
| Median value, owner-occupied | $122,700 |
| Single-family detached | 75% |
What repairs cost
Published ranges from cost guides, not quotes. More sources, and where they disagree.
Nearby counties
| Place | Distance | Expansive clay | High water table |
|---|---|---|---|
| Harding County, NM | 48 mi | 15% | 1% |
| Dallam County, TX | 51 mi | 15% | 1% |
| Cimarron County, OK | 56 mi | 22% | 2% |
| Colfax County, NM | 65 mi | 52% | 2% |
| Las Animas County, CO | 65 mi | 27% | 1% |
| Hartley County, TX | 66 mi | 14% | 1% |
| Baca County, CO | 77 mi | 28% | under 1% |
| Mora County, NM | 88 mi | 46% | under 1% |
Sources: USDA SSURGO (September 9, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status