Article

Climate and Groundwater Monitoring at Tumacácori National Historical Park: Water Year 2024

An old mission church next to adobe wall ruins next to paved paths and mown grass in a landscape of scattered trees and mountains in the distance.
Tumacácori National Historical Park

NPS/TAYLOR JONES

Overview

Together, climate and hydrology shape ecosystems and the services they provide, particularly in arid and semi-arid ecosystems. Understanding changes in climate and water is key to assessing the condition of park natural resources—and often, cultural resources.

At Tumacácori National Historical Park (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 Tumacácori National Historical Park, we monitor climate and groundwater, among other vital signs.

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 monitoring at Tumacácori National Historical Park in WY2024.

Map of Tumacácori National Historical Park showing location of a weather station near the ruins and visitor center on the western edge of the park and two groundwater wells, one at the very southern end and one on the western edge of the park.
Figure 1. Monitored weather station and groundwater wells at Tumacácori National Historical Park.

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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 (Tumacácori NM #028865) has been operational at Tumacácori National Historical Park since 1946 (Figure 1). This station typically provides a reliable climate dataset. However, in WY2024 it was missing data on 45 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.

Surreal lighting on an old mission church under a mesmerizing sunset of brilliant yellow, orange, pink, and bluish clouds filling the sky.
Sunset over the mission church, Tumacácori National Historical Park.

NPS/BOB LOVE

Results

Precipitation

Highlight: A very wet winter and slightly below average monsoon resulted in above average annual precipitation.

Annual precipitation at Tumacácori National Historical Park in WY2024 was 18.15″ (46.1 cm), 2.52″ (6.4 cm) more than the 1991–2020 annual average. This surplus primarily occurred in the cool season (October–March), during which eveyr month except November was wetter than the 1991–2020 monthly averages (Figure 2). Overall, the warm season (April–September) was drier than average by 0.5″ (1.3 cm). Only the start of the monsoon season in June and July received above average precipitation. The monsoon season then tapered off relative to the monthly averages through August and September.

Air Temperature

Highlight: It was slightly warmer than average throughout most of the year.

The mean annual maximum temperature at Tumacácori National Historical Park in WY2024 was 82.3°F (27.9°C), 1.8°F (1.0°C) above the 1991–2020 average. The mean annual minimum temperature in WY2024 was 48.7°F (9.3°C), 1.2°F (0.7°C) above the 1991–2020 average. Mean monthly maximum and minimum temperatures WY2024 differed by as much as 5.1°F (2.9°C; see July as an example) relative to the 1991–2020 monthly averages (Figure 2). Mean monthly maximum temperatures were similar to or warmer than the 1991–2020 averages in all months except January and March. Mean monthly minimum temperatures were similar to or warmer than the 1991–2020 averages in all months except May.

Climogram showing max and min temperature averages for WY2024 were higher than those for 1991–2020 for ten months. Precipitation totals for WY2024 were higher than those for 1991–2020 for October, December, January, February, March, June, and 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 Tumacácori National Historical Park. Data source: GRIDMET via climateanalyzer.org.

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Drought

Highlight: Wetter conditions 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 Tumacácori National Historical Park indicates that WY2024 was slightly wetter 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.

Bar graph showing conditions for WY2024 were wetter than average.
Figure 3. Reconnaissance drought index for Tumacácori National Historical Park, 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. Data source: GRIDMET via climateanalyzer.org.

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A narrow channel of water lined by bright green, low-growing plants and tall riparian trees.
Santa Cruz River, Tumacácori National Historical Park

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Groundwater 

Groundwater is one of the most critical natural resources of the American Southwest, providing drinking water, irrigating crops, and sustaining rivers, streams, and springs throughout the region.

Methods 

Tumacácori National Historical Park groundwater is monitored at three wells by the Arizona Department of Water (Figure 1). The Water Supply Well is manually monitored quarterly. The collocated MW-1 Deep and MW-1 Shallow wells are monitored using automated methods. Data are available at the ADWR Well Registry. 

Results

Highlight: Despite a slight decline from 2023, groundwater levels continue to trend upward since 2019.

Groundwater monitoring results for WY2024 are summarized in Table 1. Mean water level elevation at all three wells decreased slightly from WY2023, by ≤ 0.18 ft (5.5 cm). However, water levels overall in all three wells appear to be trending upward slightly (Figure 4). This increase has a few likely drivers, including (1) above average rainfall in the five of the six water years 2019–2024 and (2) increasing discharge of treated effluent from the Nogales International Wastewater Treatment Plant. Further studies and additional monitoring are needed to determine if this trend will continue and to determine the primary sources of the recharge, if recharge continues.

The MW-1 Shallow well represents the shallow unconfined aquifer and therefore has greater seasonal fluctuations over the monitoring record because of the influence of seasonal precipitation, high flow events, and evapotranspiration in the riparian area. The MW-1 Deep well represents the deeper confined aquifer, which is buffered from large rain and streamflow events, resulting in smaller magnitude fluctuations relative to the shallow aquifer. The water level in the MW-1 Deep is usually higher than in MW-1 Shallow due to elevated pressure in the confined aquifer. The Water Supply Well is also completed in the deep aquifer, but has experienced greater fluctuations, likely because this well is routinely pumped to support the park’s water needs and is located farther from the Santa Cruz River than the other monitoring wells. 

Line figure with depth to water at three wells and stream discharge, water years 1995–2024. All three show slightly increasing water levels in recent years. 
Figure 4. Depth to water feet below ground surface (ft bgs) at three groundwater monitoring at wells Tumacácori National Historical Park and daily maximum discharge at the USGS gauge, Santa Cruz River at Tubac, Arizona, 1995–2024.

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Report Citation

Author: Kara Raymond

Raymond, K. 2025. Climate and Groundwater Monitoring at Tumacácori National Historical Park: Water Year 2024. Sonoran Desert Network, National Park Service, Tucson, Arizona.

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Tumacácori National Historical Park

Last updated: November 25, 2025