Last updated: November 25, 2025
Article
Climate and Groundwater Monitoring at Saguaro National Park: Water Year 2024
NPS/HANNAH SCHWALBE
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 Saguaro National Park (Figure 1 and Figure 2), 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 Saguaro National Park, 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 Saguaro National Park 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
We report on three weather stations at Saguaro National Park (Figure 1 and Figure 2). The station at the Tucson Mountain District Visitor Center (Tucson 17 NW #028795) is a National Oceanic and Atmospheric Administration Cooperative Observer Program (NOAA COOP) weather station, that has been operational since 1982. The station at the Rincon Mountain District Visitor Center (Saguaro National Park AZ #027398) is a NOAA COOP station that has been operational since 2009 (the long-term averages used for comparison in this report are from NOAA and are based on the period of record at this station, 2009–2020). The Rincon Mountain District High Elevation station (Mica Mountain AZ #QHVA3) is a Remote Automated Weather Station (RAWS) at an elevation of 8,209 feet (2,502 m) that has been operational since 1994 (the long-term averages used for comparison in this report are based on the period of record at this station, 1994–2020).
In WY2024 the Tucson Mountain District Visitor Center station was missing data on 40 days. As a substitute, climate analyses for the Tucson Mountain District in this year’s report use 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 the weather stations and GRIDMET are accessible through Climate Analyzer.
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Results
Precipitation and Air Temperature–Tucson Mountain District Visitor Center Station (GRIDMET)
Highlights: A wet winter and strong monsoon led to above average precipitation. Temperatures were similar to 30-year averages.
Annual precipitation in WY2024 at the Tucson Mountain District Visitor Center was 14.78″ (37.5 cm), 2.78″ (7.1 cm) more than the 1991–2020 annual average. Monthly precipitation totals were similar to or above the 1991–2020 averages in most months (Figure 3). Only October, May, and September had substantial precipitation deficits. January, February, and March each received approximately twice their average precipitation totals. The monsoon started strong in June, with nearly three times its average rainfall. Above average rainfall continued through July and August before the monsoon tapered off in September.
The mean annual maximum temperature at the Tucson Mountain District Visitor Center in WY2024 was 84.5°F (29.2°C), 1.2°F (0.6°C) above the 1991–2020 average. The mean annual minimum temperature in WY2024 was 57.8°F (14.3°C), 0.4°F (0.2°C) above the 1991–2020 average. Mean monthly maximum and minimum temperatures in WY2024 differed by as much as 6.0°F (3.3°C; see December as an example) relative to the 1991–2020 monthly averages (Figure 3) and were generally cooler than average January–May and warmer than average the rest of the year.
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Results
Precipitation and Air Temperature–Rincon Mountain District Visitor Center Station (COOP).
Highlights: Precipitation was higher than average because of strong winter rains and a productive early monsoon season. Temperatures were warmer than average with three times more extremely hot days in summer months.
Annual precipitation at the Rincon Mountain District Visitor Center in WY2024 was 13.74″ (34.9 cm), 1.65″ (4.2 cm) more than the 2009 –2020 annual average. Nearly two-thirds of the annual precipitation total occurred in the cool season (October–March; Figure 4). The monsoon started strong in July with 2.81″ (7.1 cm), but tapered off in August and September, which received 0.66″ and 0.21″ (1.7 cm and 0.5 cm) respectively. Extreme daily rainfall events (≥ 1.00″; 2.54 cm) occurred on 3 days, twice the average annual frequency of 1.6 days. Extreme rainfall events occurred on 25 October 2023 (1.20″; 3.0 cm), 23 December 2023 (1.23″; 3.1 cm), and 19 July 2024 (1.00″; 2.5 cm).
The mean annual maximum temperature at the Rincon Mountain District Visitor Center in WY2024 was 85.1°F (29.5°C), 2.0°F (1.1°C) above the long-term average. The mean annual minimum temperature in WY2024 was 58.7°F (14.8°C), 1.7°F (1.0°C) above the long-term average. Mean monthly maximum and minimum temperatures in WY2024 varied up to 5.0°F (2.8°C) relative to the long-term monthly averages (Figure 4; see September as an example) and were warmer than average throughout most of the year, except during January, March, and April. Extremely hot temperatures (≥ 105.0°F; 40.6°C) occurred on 42 days in WY2024, three times the average frequency of 13.8 days. Extremely cold temperatures (≤ 36.0°F; 2.2°C) occurred on 12 days, a quarter less than the average frequency of 16 days.
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Results
Precipitation and Air Temperature–Rincon Mountain District High Elevation Station (RAWS)
Highlights: Precipitation was above average because of a wet winter and strong early monsoon season. Temperatures were similar to average most of the year.
Annual precipitation at Mica Mountain AZ in WY2024 was 23.32″ (59.2 cm), 1.10″ (2.8 cm) more than the long-term annual average. October and November were drier than average (Figure 5). Wetter than average conditions began in December and continued through April. May was completely dry. The monsoon started strong in June, which received over two and half times its long-term average, and then began to lightly taper off from July through September relative to the monthly averages. Extreme daily rainfall events (≥ 1.00″; 2.54 cm) occurred on 5 days in WY2024, similar to the average annual frequency of 4.5 days (Table 1).
| Date | Rainfall (in) | Rainfall (cm) |
|---|---|---|
| 22 December 2023 | 1.84 | 4.7 |
| 02 April 2024 | 1.07 | 2.7 |
| 20 July 2024 | 1.44 | 3.7 |
| 31 July 2024 | 1.03 | 2.6 |
| 23 August 2024 | 1.23 | 3.1 |
The mean annual maximum temperature at the Rincon Mountain District High Elevation station in WY2024 was 63.0°F (17.2°C), the same as the long-term average. The mean annual minimum temperature in WY2024 was 43.5°F (6.4°C), 1.0°F (0.5°C) above the long-term average. Mean monthly maximum and minimum temperatures WY2024 differed by as much as 7.2°F (4.0°C; see March as an example) relative to the long-term monthly averages (Figure 5). Mean monthly maximum temperatures were cooler than the long-term averages in November and January–April and warmer than average the rest of the year. Mean monthly minimum temperatures were warmer than average most of the year, except in January–March. Extremely hot temperatures (≥ 83.0°F; 28.3°C) occurred on 19 days in WY2024, similar to the average frequency of 18.6 days. Extremely cold temperatures (≤ 23.0°F; −5.0°C) occurred on 20 days, slightly below the average frequency of 21.9 days.
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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 indices for Saguaro National Park indicate that WY2024 was wetter than average at the Tucson Mountain District Visitor Center station (1991–2023, GRIDMET; Figure 6) and the Rincon Mountain District High Elevation station (1996–2023, RAWS; Figure 7). The reconnaissance drought index for the Rincon Mountain District Visitor Center station is not shown here because of many years of missing data.
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 Saguaro National Park, groundwater is monitored using four wells (Figure 1 and Figure 2). In the Tucson Mountain District, the Sonoran Desert Inventory and Monitoring Network has manually monitored WSW-1 well quarterly since 2009. Red Hills well has been monitored continuously using automated methods since 2015. In the Rincon Mountain District, park staff and volunteers have monitored Madrona Pack Base well continuously since 2011. RC-4 well has been monitored manually on a monthly basis since 2005 and continuously since WY2017.
Results
Highlight: Recent declines in groundwater levels continued across all four wells.
Groundwater monitoring results for WY2024 are summarized in Table 2. Mean groundwater levels in all four wells declined in WY2024 compared to the previous year. The water level in WSW-1 has generally increased from the 1990s until 2022 in response to recharge of Central Arizona Project (CAP) water via the Central Avra Valley Storage and Recovery Project (CAVSARP; Figure 8). From its peak in WY2022, the water level has declined nearly 30 ft (9 m). This decline is likely tied to Tucson Water recharging less CAP water at CAVSARP in 2023 and 2024 and pumping more groundwater from wells in proximity to WSW-1 during 2023. The last water level measurement in WY2024 indicated a slight recovery. However, the overall decline is an indicator of how quickly the WSW-1 aquifer responds to changes in aquifer management, including CAP water recharge amounts and groundwater pumping.
Water levels at Red Hills well declined steadily through both WY2023 and WY2024, showing only minor responses to winter rains and runoff. The lowest level was 18.80 feet below ground surface (ft bgs; 5.73 m bgs) and occurred at the end of WY2024 (Figure 9). Monsoonal rain events often recharge the shallow aquifer, causing groundwater to peak in summer, but this did not occur in WY2024.
Water levels in both the Madrona Pack Base and RC-4 wells dropped below their loggers in November and October, respectively, before increasing in January WY2024 (Figure 10). This decrease was likely due to a weak monsoon in WY2023 and an extended dry period in Rincon Creek. Both wells experienced typical fluctuations throughout the rest of WY2024.
Table 2. Groundwater monitoring results in water year (WY) 2024, Saguaro National Park (amsl = above mean sea level; bgs = below ground surface; TMD = Tucson Mountain District; RMD = Rincon Mountain District).
| Well Name | State Well Number | Park Unit | Wellhead Elevation (ft amsl) | Mean Depth to Water (ft bgs) | Mean Water Level Elevation (ft amsl) |
Elevation Change from WY2023 (± ft) |
|---|---|---|---|---|---|---|
| WSW-1 | 629094 | TMD | 2,336.00 | 319.83 | 2,016.17 | −15.63 |
| Red Hills | 629095 | TMD | 2,795.00 | 16.71 | 2,778.29 | −5.38 |
| Madrona Pack Base | 629099 | RMD | 3,350.00 | 18.28 1 | 3,331.72 1 | −7.61 1 |
| RC-4 | 206880 | RMD | 3,150.42 | 6.64 2 | 3,143.78 2 | −0.79 2 |
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Report Citation
Author: Kara Raymond
Raymond, K. 2025. Climate and Groundwater Monitoring at Saguaro National Park: Water Year 2024. Sonoran Desert Network, National Park Service, Tucson, Arizona.