Alamosa County, Colorado
A shallow water table limits basements on 36% of Alamosa County's mapped land, a higher share than 54% of US counties and the 2nd highest of 63 Colorado counties. Shrink-swell clay limits houses without basements on 2%.
100% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 1 flood losses here since 2016. 47% of homes were built before 1980, against 50% nationally; the median home dates from 1982.
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 Alamosa County
| Expansive clay (limits slab homes) | 1.9% |
| High water table (limits basements) | 35.5% |
| Septic fields very limited | 84.8% |
| Clay swell (LEP, by area) | 2.8% |
| High-swell land (LEP 6%+) | 13.8% |
| Mapped soil | 462,524 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Hooper | 14% | n/a |
| Gunbarrel | 11% | n/a |
| Mosca | 8% | n/a |
| San Luis | 8% | n/a |
| Space City | 7% | n/a |
| Corlett | 5% | n/a |
How we count · survey areas CO632 (2025-08-29), CO634 (2025-08-29)
What the numbers mean here
On 36% of Alamosa County's mapped land, soil stays saturated within about 6 feet of the surface for part of the year, which is basement depth.
Rain over the 12 months to August 2026: 7.32 in, 3.39 in below the 1991-2020 average year of 10.71 in.
USDA rates 85% of the land very limited for septic absorption fields.
Drought
100% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 52 of the last 52 weeks; the most was 100% of its area, in 29 weeks, most recently on the October 13, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 100% |
| D1 moderate drought or worse | 100% |
| D2 severe or worse | 100% |
| D3 extreme or worse | 14.1% |
| D4 exceptional | 0% |
Flood losses since 2016
1 flood losses since 2016, $0 paid. The worst year was 2019, with 1.
| Year | Flood losses |
|---|---|
| 2016 | 0 |
| 2017 | 0 |
| 2018 | 0 |
| 2019 | 1 |
| 2020 | 0 |
| 2021 | 0 |
| 2022 | 0 |
| 2023 | 0 |
| 2024 | 0 |
| 2025 | 0 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 10.71 in |
| 12 months to August 2026 | 7.32 in (-3.39) |
| 2025 | 10.48 in (-0.23) |
| Wettest year since 1895 | 2024: 16.76 in |
| Driest year since 1895 | 1950: 5.61 in |
| Days with 1 inch or more, normal at ALAMOSA SAN LUIS AP (10 mi away) | 0.3 |
Homes
| Housing units | 7,241 |
| Median year built | 1982 |
| Built before 1980 | 47% |
| Built 2000 or later | 27% |
| Owner-occupied | 56% |
| Median value, owner-occupied | $239,100 |
| Single-family detached | 61% |
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 |
|---|---|---|---|
| Costilla County, CO | 28 mi | under 1% | 4% |
| Conejos County, CO | 32 mi | under 1% | 28% |
| Rio Grande County, CO | 37 mi | under 1% | 42% |
| Saguache County, CO | 40 mi | 4% | 15% |
| Custer County, CO | 43 mi | 2% | 7% |
| Huerfano County, CO | 46 mi | 13% | 2% |
| Mineral County, CO | 64 mi | 1% | 5% |
| Fremont County, CO | 64 mi | 5% | 2% |
Sources: USDA SSURGO (August 29, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status