Article

Climate and Groundwater Monitoring at Organ Pipe Cactus National Monument: Water Year 2024

A brilliant orange, yellow, and purple sunset with a radial pattern of light and shadow over purple mountains and dark silouhettes of cactus on a rolling landscape.
Sunset in Organ Pipe Cactus National Monument

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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 Organ Pipe Cactus 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 Organ Pipe Cactus 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 Organ Pipe Cactus National Monument in WY2024.

Map of Organ Pipe Cactus National Monument showing one weather station at headquarters and 8 groundwater monitoring wells. Five are close to the US-Mexico border, while three are farther north.
Figure 1. Monitored weather station and groundwater wells at Organ Pipe Cactus National Monument.

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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 (Organ Pipe Cactus Natl Mon AZ ID# 026132) has been operational at Organ Pipe Cactus National Monument since 1944 (Figure 1). This station provides a reliable, long-term climate dataset for analyses in this climate and water report. Data from this station are accessible through Climate Analyzer.

A carpet of yellow flowers among scattered desert shrubs, cacti, and exposed rock on a rolling landscape in front of a sharply pointed small mountain under a mostly blue sky.
Carpet of wildflowers near Dripping Springs, Organ Pipe Cactus National Monument.

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Results

Precipitation

Highlight: A wet winter and spring resulted in above average annual precipitation.

Annual precipitation at Organ Pipe Cactus National Monument in WY2024 was 10.62″ (27.0 cm), 1.34″ (3.4 cm) more than the 1991–2020 annual average. Rainfall may be slightly underestimated because of missing data in April. Little to no precipitation occurred in October and November (Figure 2). Following this was a very wet winter and early spring. Monthly precipitation totals in December–April were above the 1991–2020 monthly averages by up to 0.76″ (1.9 cm). May was completely dry. Overall, the precipitation total for the monsoon season (June–September) was approximately the same as average. However, the monsoon started and ended earlier than normal. June received over nine times its monthly average. Rainfall totals in July and August were slightly above and below their monthly averages, respectively, and September was completely dry. Extreme daily rainfall events (≥ 1.00″; 2.54 cm) occurred on 3 days, one more than the average annual frequency of 2.1 days. Extreme rainfall events occurred on 22 December 2023 (1.52″; 3.9 cm), 23 January 2024 (1.28″; 3.3 cm), and 11 August 2024 (1.20″; 3.0 cm).

Air Temperature

Highlight: Temperatures were slightly warmer than average with more extremely hot summer days.

The mean annual maximum temperature at Organ Pipe Cactus National Monument in WY2024 was 88.2°F (31.2°C), 0.8°F (0.5°C) above the 1991–2020 average. The mean annual minimum temperature in WY2024 was 57.9°F (14.4°C), 1.4°F (0.8°C) above the 1991–2020 average. Mean monthly maximum and minimum temperatures in WY2024 differed by as much as 4.0°F (2.2°C; see October as an example) relative to the 1991–2020 monthly averages (Figure 2) and were warmer than the averages in seven months. Cooler than average temperatures occurred primarily during the winter and early spring. Extremely hot temperatures (≥ 107.0°F; 41.7°C) occurred on 37 days in WY2024, approximately two-thirds more than the average frequency of 21.8 days. Extremely cold temperatures (≤ 35.0°F; 1.7°C) occurred on 7 days, approximately a third of the average frequency of 20.1 days.

Climogram showing maximum and minimum temperature averages for WY2024 are higher than those for 1991–2020 in seven months. Monthly precipitation totals for WY2024 are higher than those for 1991–2020 for December–April and June–July.
Figure 2. Climogram showing monthly precipitation and mean maximum and minimum air temperatures in water year (WY) 2024 and the 1991–2020 averages at Organ Pipe Cactus National Monument. Temperature data were not available for April because of insufficient data. Data source: climateanalyzer.org.

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Drought

Highlight: Data were insufficient for assessing drought in 2024.

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 Organ Pipe Cactus National Monument could not be calculated in WY2024 because of insufficient data (Figure 3).

Reference: Tsakiris G., and H. Vangelis. 2005. Establishing a drought index incorporating evapotranspiration. European Water 9: 3–11.

Bar graph showing departures from average wet/dry conditions in years prior to WY2024. In WY2024, an RDI was not available.
Figure 3. Reconnaissance drought index for Organ Pipe Cactus Natl Mon AZ station at Organ Pipe Cactus National Monument, water years (WY) 1991–2024. Drought index calculations are relative to the time period selected (1990–2024). Choosing a different set of start/end points may produce different results. N/A = insufficient data to generate reliable estimates. Data source: climateanalyzer.org.

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Tall cactus columns clumped together in multiple groups on a desert hillside of shrubs and other cacti.
Organ pipe cactus

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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 Organ Pipe Cactus National Monument, groundwater is monitored using eight wells : Bates, Bonita, Corner, Headquarters #5, Stack, USGS #1, USGS #2, and USGS #3 (Figure 1). All wells are monitored using manual methods quarterly to annually by park staff, except for Headquarters #5, which is monitored annually by the Arizona Department of Water Resources (ADWR). ADWR data are available from the ADWR Well Registry.  In WY2020, continuous monitoring began at four wells: Bates, Headquarters #5, USGS #2, and USGS #3. Continuous monitoring ended at Headquarters #5 in WY2023 due to equipment failure.

Results

Highlight: Groundwater declined in all eight wells, with half having the lowest water levels on record.

Average groundwater levels in all eight wells decreased between WY2023 and WY2024 (Table 1, Figure 4). Declines from the previous year at Bates #2 and Bonita were high, 8.10 ft (2.47) and 4.30 ft (1.31 m), respectively. However, water levels at these two wells were within the range of the monitoring record throughout WY2024. Declines at the other six wells were ≤ 1.54 ft (0.47 m). Four of the wells recorded their lowest water level of the monitoring record in WY2024: Stack, USGS #1, USGS #2, and USGS #3.

  • Overall Stack, USGS #1, and USGS #2 wells have shown similar rates of decline over the monitoring record, with seasonal fluctuations likely related to groundwater pumping south of the US–Mexico border.

  • Headquarters #5 has shown similar rates of decline but there is no evidence of seasonal fluctuations. While the depth to water at Headquarters #5 is much larger than the other wells, its water level elevation is slightly higher, indicating that it is upgradient and within the same aquifer as the Stack, USGS #1, and USGS #2 wells.

  • The groundwater level in Corner well has also been declining but much more gradually.

  • Groundwater levels in Bates #2 and Bonita, which are both shallow wells, have been more variable over the monitoring record, indicating that these wells are more impacted by precipitation and local recharge and less impacted by groundwater withdrawals.

  • The groundwater level in USGS #3 has only varied by 12.64 ft (3.85 m) over the monitoring period; however, a decline starting in WY2020 has been more rapid than prior periods. The water level at USGS #3 is now exhibiting slight seasonal fluctuations. Geologic activity and groundwater withdrawals in the area—potentially including nearby wells used in concrete production to support wall construction—may be the cause of this recent decline in USGS #3.

Line graph showing six wells exhibit decreasing water levels. Two wells show more shallow water levels with greater fluctuation.
Figure 4. Depth to water in feet below ground surface (ft bgs) at eight groundwater monitoring wells at Organ Pipe Cactus National Monument, 1976–2024. Depth to water for Headquarters #5 is shown on the right axis. Depth to water for all other wells is shown on the left axis. Measurements taken while groundwater pumping occurred at Headquarters #5 well are shown as green squares with white fill. Blue circles with white fill indicate when Bonita well was dry.

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Report Citation

Author: Kara Raymond

Raymond, K. 2025. Climate and Groundwater Monitoring at Organ Pipe Cactus National Monument: Water Year 2024. Sonoran Desert Network, National Park Service, Tucson, Arizona.

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Organ Pipe Cactus National Monument

Last updated: November 25, 2025