Saguaro National Park has two districts: the Tucson Mountain District (TMD) and the Rincon Mountain District (RMD). The National Park Service's Sonoran Desert Network tracks a set of "vital signs" there every year — measurements that, like a patient's pulse and temperature, can flag a problem early enough for managers to act. Climate, groundwater and springs are three of them, and the network reports them together because desert water depends so closely on weather.
The report runs by water year: water year 2021 (WY2021) began on October 1, 2020 and ended on September 30, 2021.
Weather stations and wells monitored in the Tucson Mountain District, WY2021 (NPS).
Weather stations, wells and springs monitored in the Rincon Mountain District, WY2021 (NPS).
The weather: dry months, then a wet monsoon
The park has two Cooperative Observer Program weather stations, one near each visitor center (the TMD station since 1982, the RMD station since 2008). In WY2021 both had large gaps — 346 missing days at the TMD station and 48 at the RMD station — so the report used GRIDMET instead: a gridded climate dataset at 4-kilometer resolution, built from weather stations, terrain and other observations. It can differ from the weather at any single spot. A remote automated weather station (RAWS) covers the high country of the Rincon Mountains.
| TMD visitor center | RMD visitor center | Rincon high country (RAWS) | |
|---|---|---|---|
| Precipitation | 13.91" | 18.58" | 28.55" |
| Compared with the average | +1.91" | +5.41" | +6.33" |
| Rain in July–August | 11.26", over four times the usual | 14.02", nearly three times the usual | 22.53", 79% of the year's total |
| Average maximum temperature | 83.9°F (+0.5°F) | 83.9°F (+1.2°F) | 62.6°F (−0.3°F) |
| Average minimum temperature | 57.0°F (−0.4°F) | 55.7°F (+1.5°F) | 43.8°F (+1.2°F) |
Averages are 1991–2020 at the visitor centers and 1995–2020 at the RAWS station.
At all three sites the pattern was the same: most months before the monsoon were drier than normal, and July and August more than made up for it. In the mountains, every month from October through June had less than an inch of rain. Then came nine days with an inch or more — twice the usual 4.5 — including 3.21" on August 14, 2021. The mountain station also logged 11 days above 83°F, fewer than its average of 18.6, and 21 days below 23°F, close to its average of 21.9.
Monthly precipitation and temperatures at the TMD visitor center, WY2021 against the 1991–2020 means. Data: GRIDMET via Climate Analyzer (NPS).
The same comparison at the RMD visitor center (NPS).
Monthly precipitation and temperatures at the high-elevation RAWS station in the Rincon Mountains, WY2021 (NPS).
A reconnaissance drought index, which weighs precipitation against potential evapotranspiration (how much water evaporation and plants would remove if water were unlimited), put WY2021 on the wet side of average at every site. The RMD, both low and high, came out wetter than the TMD.
Groundwater: four wells
| Well | District | Monitored | WY2021 mean depth to water | Change from WY2020 |
|---|---|---|---|---|
| WSW-1 | TMD | quarterly by hand since 2009 | 306.35 ft | +6.19 ft |
| Red Hills | TMD | continuously since 2015 | 14.65 ft | −3.70 ft |
| Madrona Pack Base | RMD | continuously since 2011 | one reading only | — |
| RC-4 | RMD | monthly since 2005, continuously since WY2017 | dry | — |
- WSW-1 stood 180.51 feet higher than its lowest level, reached in 2005. The aquifer is recovering because Central Arizona Project water is being recharged into it through the Central Avra Valley Storage and Recovery Project.
- Red Hills, which draws on a shallow aquifer, fell steadily into the summer, bottoming out at 19.19 feet below the surface in July. Monsoon storms then refilled it to 2.27 feet in August.
- The Rincon wells have incomplete records for the year because equipment failed. Madrona Pack Base's single manual reading was within the well's historic range. RC-4 was dry for the whole stretch with data (October 1 to November 4, 2020); it has been dry for part of 11 of the past 17 water years. Both wells tend to rise after enough rain and runoff in the Rincon Creek watershed.
Depth to water at WSW-1, 1964–2021. The rise after 2005 reflects recharge from the Central Avra Valley Storage and Recovery Project (NPS).
Depth to water at the Red Hills well and daily precipitation, WY2015–2021 (NPS).
Springs: small places that matter a great deal
In a desert, springs, seeps and tinajas (pools held in rock basins) are rare hotspots of life and the main place groundwater reaches the surface. The network's key questions are how long a spring held water and how much. It answers them in four parts:
- Site characterization — location, a sketch, the spring type and its plants, redone every five years or after a major event. Spring types include rheocrene (emerging as a flowing stream), limnocrene (a pool) and helocrene (a wetland).
- Site condition — each disturbance, natural or human, is scored from 1 (undisturbed) to 4 (highly disturbed), and crews watch for invasive plants and for non-native bullfrogs and crayfish.
- Water quantity — temperature loggers show when a spring was wet (water damps the daily swing), plus timed flow samples and the length, width and depth of surface water.
- Water quality — temperature, pH, conductivity, dissolved oxygen, dissolved solids and major ions.
Climate change is expected to bring hotter air, faster evaporation, harsher droughts and more extreme storms to Southwestern springs, and possibly less winter and spring rain — enough to shrink some springs or dry them out.
Low elevation: visited April 5–7, 2021
Chimenea 1L, April 2021, one of at least 15 tinajas in lower Chimenea Canyon (NPS photos).
- Chimenea 1L held water on all 188 days recorded before the visit and flowed at 2.1 (± 0.5) liters a minute, much as in WY2018; it had no measurable flow in WY2019.
- Javelina Tank also held water on every recorded day (187), but two of its sampling locations were dry, so drying rose to a moderate disturbance for the first time. Three invasive grasses grew in scattered patches: red brome, crimson fountaingrass and rose natal grass.
- Wild 10G Tinaja had water but no outflow — the first time drying was noted there. Its sensors failed two months into the year. The same three invasive grasses were present.
High elevation: the Rincon Mountains, visited May 27–31, 2021
Boulder, Bulrush, Cabin and Manna Grass springs were sampled for the first time in WY2021.
| Spring | On the day of the visit | What the crew noted |
|---|---|---|
| Boulder | Dry | Unexpected. Normally it rises from under the roots of a ponderosa pine; charred and fallen trees lined the drainage |
| Bulrush | Water, negligible flow; brook 21 m | Trees charred by fire |
| Cabin | Water, no surface flow; brook 2 m | The source pool looks like an old springbox. Wetland plants grazed; tracks of deer, raccoon and ringtail. Common dandelion |
| Deer Head | Dry | Highly disturbed by drying; drying and flooding noted for the first time. Its channel is thought to have been kept clear for people and pack animals until the Saguaro Wilderness was created in 1976 |
| Italian | A pool of about 2 × 3 × 1 cm | Wet 232 of 239 days (97.1%). Drying recorded for the first time |
| Manna Grass | Water; 0.3 liters a minute; brook 39 m | In forest burned by the Helen's 2 Fire (2004). A few Kentucky bluegrass plants |
| Manning Camp Reservoir | Water, all 242 recorded days | A dammed pool that supplies Manning Camp's drinking water, dredged from time to time; depth isn't measured so the water isn't contaminated |
| Mica Meadows Trail Seep 1 | Dry | Pools filled with sediment after fire; drying and flooding noted for the first time. Sensors had shown water on all 80 days before they failed |
| Mud Hole | Water; 0.3 liters a minute; brook 11 m | A human-built, rock-lined pool; footprints around it. First year drying was noted |
| New Spring 3 | Dry | Sensors read wet for all 216 days, so some readings were false. Its worst ratings yet for drying and fire |
| Spud Rock | Dry | Wet 181 of 241 days (75.1%). Part of the dismantled Spud Rock Cabin and farm, whose springbox once piped water to a second pool. Dandelion seen for the first time |
| Upper Joaquin | Water; brook 16 m, shorter than before | Fire damage in the forest around it. Slight drying noted for the first time; lobelia seen for the first time |
Cabin Spring, May 2021 (NPS photo).
Spud Rock Spring, May 2021 (NPS photo).
The springs, May 2021
Storm over Saguaro National Park (NPS).
Figure 3. Left: Javelina Tank, sampling location 001 and orifice A, Saguaro National Park, April 2021. Right: Location of Javelina Tank below a bedrock cliff, with additional smaller tinajas in the channel below. NPS photos.
Figure 5. Left: Wild 10G Tinaja, sampling location 001 and orifice A, Saguaro National Park, April 2021. Right: Wild10G is located in a complex of tinajas in Wildhorse Canyon. NPS photos.
Figure 7. Boulder Spring at Saguaro National Park, May 2021. NPS photo.
Figure 8. Bulrush Spring at Saguaro National Park, May 2021. NPS photo.
Figure 10. Deer Head Spring at Saguaro National Park, May 2021. NPS photo.
Figure 11. Italian Spring at Saguaro National Park, May 2021. NPS photo.
Figure 13. Manna Grass Spring at Saguaro National Park, May 2021. NPS photo.
Figure 14. Manning Camp Reservoir at Saguaro National Park, May 2021. NPS photo.
Figure 16. Mica Meadows Trail Seep 1 at Saguaro National Park, May 2021. NPS photo.
Figure 18. Mud Hole Spring at Saguaro National Park, May 2021. NPS photo.
Figure 20. New Spring 3 at Saguaro National Park, May 2021. NPS photo.
Figure 24. Upper Joaquin Spring at Saguaro National Park, May 2021. NPS photo.
Sources
- National Park Service, Sonoran Desert Network: "Climate and Water Monitoring at Saguaro National Park, Water Year 2021" (report by Kara Raymond, Andy Hubbard, Cheryl McIntyre and Laura Palacios). The source gives Madrona Pack Base's reading as 21.39 feet in the text and 21.38 feet in its table, so neither is stated here. It prints the mountain station's mean low as "43.8.0°F (6.6°C)", corrected here to 43.8°F. Its drought-index figure for the RMD repeats the TMD chart, so the drought charts are not reproduced. Pictures an earlier version of this page left out were restored on 2026-09-26.
In these publicationsSaguaro National Park
Licence: CC0 1.0 (public domain) · Adapted from www.nps.gov
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