A climate station above the Salt River Valley. Image from the National Park Service's page
Tonto National Monument, in central Arizona, protects cliff dwellings high above the Salt River Valley. Their location tells of the value of reliable water: the Tonto Basin's year-round waters, rich alluvial soils and varied natural resources drew people of the Salado culture, who lived in the dwellings for about 300 years, until around A.D. 1450.
Because climate, groundwater and surface water are closely linked, the NPS Sonoran Desert Network monitors all three here — to catch broad-scale change and give park managers early warning of problems. It reports by water year, which runs from October to the following September.
Climate: a dry year
Monthly precipitation compared with the 30-year normal (1981–2010), Repeater Ridge station, water year 2018. Image from the National Park Service's page
| Water year 2018 | |
|---|---|
| Total precipitation | 32% of normal |
| Fall and winter | 20.3% of normal, 8.42 inches short; October and November completely dry |
| Spring and summer | about half of normal, though June was above normal thanks to a single 0.33-inch storm |
| Largest storm | 0.49 inch, August 12 |
| Cool season | 31.9–90.4 °F |
| Warm season | 47.0–106 °F |
| Very cold days (below 35 °F) | five; below freezing for a full 24 hours just once |
More data: The Climate Analyzer.
Groundwater
The piezometer at the shallow groundwater site on Cave Canyon Creek. NPS/Jacob DeGayner
| Site | Water year 2018 |
|---|---|
| Cave Canyon Creek | mean water level 1.03 feet above the sensor; rose with winter rains, fell through the dry, warm months, and rose again once the monsoon began |
| Cinda's Seep | never rose above the sensor; in the record, the shallow water table topped the sensor only in winter or early spring of WY2010–2012 |
Springs
Cave Canyon Spring is a rheochrene spring, dominated by runoff. Surveys rated it undisturbed by both human and natural causes, temperature sensors showed it wet throughout sampling, and all water quality and chemistry measures were within the expected range.
Sources
Based on "Climate and Water Monitoring at Tonto National Monument, Water Year 2018," National Park Service, summarizing E. L. Gwilliam, L. Palacios and K. Raymond, Status of Climate and Water Resources at Tonto National Monument: Water Year 2018 (2019); a work of the United States government in the public domain. The article gives June's rainfall as both over four times and 250% of normal, so no figure is given here.
Licence: CC0 1.0 (public domain) · Adapted from www.nps.gov
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