Last updated: August 26, 2025
Article
Climate and Water Monitoring at Fort Union National Monument: Water Year 2024
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Overview
Together, climate and hydrology shape ecosystems and the services they provide, particularly in arid and semi-arid ecosystems and across the Southern Plains (Woodhouse and Overpeck 1998). Understanding changes in climate, groundwater, and surface water is key to assessing the condition of park natural resources—and often, cultural resources.
At Fort Union National Monument (Figure 1), Southern Plains Inventory and Monitoring Network scientists study how ecosystems may be changing by taking measurements of key resources, or “vital signs,” year after year—much as a doctor keeps track of a patient’s vital signs. This long-term ecological monitoring provides early warning of potential problems, allowing managers to mitigate them before they become worse. At Fort Union National Monument, we monitor climate and groundwater, among other vital signs.
Groundwater conditions are closely related to climate conditions. Because they are better understood together, we report on climate in conjunction with water resources. Reporting is by water year (WY), which begins in October of the previous calendar year and goes through September of the water year (e.g., WY2024 runs from October 2023 through September 2024). This web report presents the climate and groundwater monitoring results for Fort Union National Monument in WY2024.
Reference: Woodhouse, C. A., and J. T. Overpeck. 1998. 2000 years of drought variability in the central United States. Bulletin of the American Meteorological Society 79(12): 2693–2714. https://doi.org/10.1175/1520-0477(1998)079%3C2693:YODVIT%3E2.0.CO;2
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Climate and Weather
There is often confusion over the terms “weather” and “climate.” In short, weather describes instantaneous meteorological conditions (e.g., it’s currently raining or snowing, it’s a hot or frigid day), and climate reflects patterns of weather at a given place over longer periods of time (seasons to years). Climate is the primary driver of ecological processes on earth. Climate and weather information provide context for understanding the status or condition of other park resources.
Methods
The closest weather station to Fort Union National Monument is 19 miles (31 km) away. As a substitute, climate analyses in this report use current year and 30-year averages (1991–2020) of gridded surface meteorological (GRIDMET) data from the location of the Fort Union National Monument Visitor Center.
GRIDMET is a spatial climate dataset at a 4-kilometer resolution that is interpolated using weather station data, topography, and other observational and modeled land surface data. Temperature and precipitation estimated from GRIDMET may vary from actual weather at a particular location, depending on the availability of weather station data and the difference in elevation between the location of interest and that assigned to a grid cell. Data from the weather station 19 miles from the park and GRIDMET are available through Climate Analyzer.
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Results
Precipitation
Annual precipitation at Fort Union National Monument in WY2024 was 18.66″ (47.4 cm), 1.28″ (3.3 cm) more than the 1991–2020 annual average. Precipitation totals in December, March, and June were substantially wetter than the 1991–2020 averages by up to 1.87″ (4.7 cm; Figure 2). November, April, and September were substantially drier than the averages, by up to 0.88″ (2.2 cm). Monthly precipitation during the other six months was similar to the long-term averages.
Air Temperature
The mean annual maximum temperature at Fort Union National Monument in WY2024 was 65.8°F (18.8°C), which is exactly the same as the 1991–2020 average. The mean annual minimum temperature in WY2024 was 35.1°F (1.7°C), 2.1°F (1.1°C) above the 1991–2020 average. Mean monthly maximum and minimum temperatures for WY2024 differed by as much as 5.4°F (3.0°C; see June as an example). However, mean monthly maximum temperatures were within 2.0°F (1.1°C) of the 1991–2020 monthly averages during most of the year (Figure 2). Mean monthly minimum temperatures were above or similar to average the entire year.
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Drought
Reconnaissance drought index (Tsakiris and Vangelis 2005) provides a measure of drought severity and extent relative to the long-term climate. It is based on the ratio of average precipitation to average potential evapotranspiration (the amount of water loss that would occur from evaporation and plant transpiration if the water supply was unlimited) over short periods of time (seasons to years). The reconnaissance drought index for Fort Union National Monument indicates that WY2024 was wetter than the 1991–2024 average from the perspective of both precipitation and potential evapotranspiration, after a four-year period of drier than average conditions (Figure 3).
Reference: Tsakiris G., and H. Vangelis. 2005. Establishing a drought index incorporating evapotranspiration. European Water 9: 3–11.
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Groundwater
Groundwater is one of the most critical natural resources of the American Southwest and Southern Plains. It provides drinking water, irrigates crops, and sustains rivers, streams, and springs throughout the region.
Methods
At Fort Union National Monument, groundwater is monitored using one well (WL-0257; Figure 1). The New Mexico Bureau of Geology and Mineral Resources began monitoring the well in 2022. The data are available at the Healy Collaborative Groundwater Monitoring Network.
Results
Groundwater level was measured once in WY2024 at 93.15 feet below ground surface (ft bgs; 28.39 m bgs) on 10 May 2024 (Table 1 and Figure 4). This measurement is the highest of the four-year record and may represent a recovery from the previous two years. Additional data will be needed to better understand normal groundwater fluctuations at this well.
Table 1. Groundwater monitoring results in water year (WY) 2024, Fort Union National Monument (amsl = above mean sea level; bgs = below ground surface).
| State Well Number | Location | Wellhead Elevation (ft amsl) |
Mean Depth to Water (ft bgs) |
Mean Water Level Elevation (ft amsl) |
Change in Elevation from WY2023 (± ft) |
|---|---|---|---|---|---|
| WL-0257 | Fort Union National Monument | 6,719.00 | 93.15 | 6,625.85 | +5.36 |
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Report Citation
Authors: Kara Raymond, Andy Ray
Raymond, K., and A. Ray. 2025. Climate and Water Monitoring at Fort Union National Monument: Water Year 2024. Southern Plains Network, National Park Service, Pecos, New Mexico.