Last updated: November 25, 2025
Article
Climate and Groundwater Monitoring at Montezuma Castle 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. Understanding changes in climate, groundwater, and surface water is key to assessing the condition of park natural resources—and often, cultural resources.
At Montezuma Castle National Monument (Figure 1), Sonoran Desert 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 resource problems, allowing managers to mitigate them before they become worse. At Montezuma Castle 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 groundwater. 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 results of climate and groundwater monitoring at Montezuma Castle National Monument in WY2024.
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Climate and Weather
There is often confusion over the terms “weather” and “climate.” Weather describes short-term 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
A National Oceanic and Atmospheric Administration Cooperative Observer Program (NOAA COOP) weather station (Montezuma Castle Natl Mon AZ #025635) has been operational at Montezuma Castle National Monument since 1938 (Figure 1). This station typically provides a reliable climate dataset. However, in WY2024 it was missing data on 32 days. As a substitute, climate analyses in this year’s report use WY2024 and 30-year averages (1991–2020) of gridded surface meteorological (GRIDMET) data from the location of the station. Subsequent reports may revert to the weather station as the data source, depending on future data quality.
GRIDMET is a spatial climate dataset (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 both the weather station and GRIDMET are accessible through Climate Analyzer.
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Results
Precipitation
Highlight: Precipitation was below average as the strong start to the monsoon season rapidly dwindled.
Annual precipitation at Montezuma Castle National Monument in WY2024 was 10.56″ (26.8 cm), 2.52″ (6.4 cm) less than the 1991–2020 annual average. Monthly precipitation totals in WY2024 were less than the 1991–2020 averages in all months except February, March, and June (Figure 2). The monsoon season started strong in June, which received over seven times its average rainfall. The monsoon then tapered off through September.
Air Temperature
Highlight: It was warmer than average.
The mean annual maximum temperature at Montezuma Castle National Monument in WY2024 was 81.5°F (27.5°C), 1.1°F (0.6°C) above the 1991–2020 average. The mean annual minimum temperature in WY2024 was 45.2°F (7.3°C), 0.5°F (0.3°C) above the 1991–2020 average. Mean monthly maximum and minimum temperatures in WY2024 differed by as much as 6.7°F (3.7°C; see June as an example) relative to the 1991–2020 monthly averages (Figure 2). Mean monthly maximum temperatures in WY2024 were warmer than average during most of the year except in January–April. Mean monthly minimum temperatures were within 2.0°F (1.1°C) of the long-term average, except in June, which was substantially warmer than average.
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Drought
Highlight: Increasing drought conditions.
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 Montezuma Castle National Monument indicates WY2024 was drier than the 1991–2024 average from the perspective of both precipitation and potential evapotranspiration (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. It provides drinking water, irrigates crops, and sustains rivers, streams, and springs throughout the region.
Methods
At Montezuma Castle National Monument, groundwater is monitored using three wells: the water supply wells (WSW) for both the Castle and Well units, and a third well (ADWR Index) outside the Well unit (Figure 1). Each well is monitored annually by the Arizona Department of Water Resources (ADWR); data are available at ADWR Well Registry.
Results
Highlight: Steady declines in groundwater continued at Montezuma Well, while groundwater levels at Montezuma Castle were inconclusive.
Groundwater monitoring results for WY2024 are summarized in Table 1. Water levels in the Montezuma Well WSW and the ADWR Index well decreased in WY2024 from the previous year by 24.4 feet (7.4 m) and 12.6 feet (3.8 m), respectively (Figure 4). However, the Montezuma Well WSW was pumping at the time of measurement and is likely not representative of static water level. The Montezuma Castle WSW has fluctuated by a range of 44.1 feet (13.4 m) over the monitoring record and has been generally stable since the monitoring well was established in 1958. Water levels in this well are likely regulated by flow in adjacent Beaver Creek. The monitoring records at both the Montezuma Well WSW and ADWR Index well demonstrate steady declines.
Table 1. Groundwater monitoring results in water year (WY) 2024, Montezuma Castle National Monument (amsl = above mean sea level; bgs = below ground surface; WSW = water supply well; ADWR = Arizona Department of Water Resources; NA = not available).
| Well Name | State Well Number | Wellhead Elevation (ft amsl) |
Depth to Water (ft bgs) |
Water Level Elevation (ft amsl) |
Elevation Change from WY2023 (± ft) |
Elevation Change (± ft) from Earliest Recorded Water Level through WY2024 (year) |
|---|---|---|---|---|---|---|
| Montezuma Castle WSW 1 | 629124 | 3,190.00 | NA | NA | NA | NA |
| Montezuma Well WSW | 629125 | 3,515.00 | 160.2 2 | 3,354.80 | −24.4 | −134.2 (1970) |
| ADWR Index | 514006 | 3,580.00 | 193.4 | 3.386.60 | −12.6 | −79.2 (2003) |
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Report Citation
Author: Kara Raymond
Raymond, K. 2025. Climate and Groundwater Monitoring at Montezuma Castle National Monument: Water Year 2024. Sonoran Desert Network, National Park Service, Tucson, Arizona.