Climate and Water at Organ Pipe Cactus National Monument, Water Year 2018

Monitoring a tinaja at Organ Pipe Cactus National Monument. Image from the National Park Service's page.

Climate, groundwater and surface water are closely linked, so the National Park Service's Sonoran Desert Network monitors all three at Organ Pipe Cactus National Monument, to track broad change and warn park managers early of problems. Reports follow the water year, which runs from October to the following September.

The monument and its water

Organ Pipe Cactus is one of the most biologically diverse protected areas in the Sonoran Desert, home to many desert-adapted plants and animals, including numerous threatened and endangered species. It is recognized as a globally important biosphere reserve, and its cultural resources reflect the long presence of Native American, Mexican and Anglo peoples.

Most of its key surface-water features are tinajas. Three spring complexes — Quitobaquito, Bull Pasture and Dripping Springs — flow year-round, fed by groundwater. These scattered, isolated waters are vital aquatic habitat and support the surrounding desert. Park staff and cooperators have measured groundwater since 1977.

Climate: a dry year

Departures from 1981–2010 normal minimum and maximum temperature and precipitation, water year 2018. NPS figure.

• Total precipitation was 44% of normal (based on 1981–2010).
• The cool season (October–March) was especially dry, with just 18% of normal — 4.07 inches below.
• Most of the year's rain fell in July. Apart from June, every other month got 0–45% of normal.
• Temperatures ran warmer than normal, with fewer extremely cold days.
• A drought index showed the regional drought that began in 2000 continuing through the year.

Groundwater: still falling

Monitored wells, water year 2018. NPS figure.

All nine monitored wells dropped from the year before, by 0.18 to 1.70 feet, and six reached their lowest levels on record (a seventh was dry). Six wells — Headquarters #5, Kalil, Stack, USGS #1, USGS #2 and Corner — show a general long-term decline. All but Corner are falling at similar rates, partly because of seasonal groundwater pumping for agriculture south of the U.S.–Mexico border. Records at Bates #2, Bonita and USGS #3 vary more, pointing to local influences.

Depth to water at ten wells, 1976–2018; measurements taken during pumping are shown in red, dry readings in white. NPS figure.

Springs

The network monitors four springs and tinajas:

• Dripping Springs and Quitobaquito Spring held water all year.
• Displaced sensors meant no reliable water-quantity data at the other two, East Arroyo Tinaja and Snake Pit Tinaja.
• Water quality was within the expected range everywhere.
• Dripping Springs and both tinajas were rated undisturbed by people or nature. Quitobaquito showed slight human disturbance from park staff's efforts to keep water flowing to Quitobaquito Pond.

East Arroyo Tinaja. Image from the National Park Service's page.

Water levels at Quitobaquito Pond are a long-standing concern. It is designated critical habitat for the endangered Quitobaquito pupfish (Cyprinodon eremus) and provides water and habitat for the endangered Sonoyta mud turtle (Kinosternon sonoriense longifemorale) and many other species.

Sources

• National Park Service, Sonoran Desert Network: "Climate and Water Monitoring at Organ Pipe Cactus National Monument, Water Year 2018."
• Raymond K, Palacios L, McIntyre C, Gwilliam EL. 2019. Status of climate and water resources at Organ Pipe Cactus National Monument: Water year 2018; and the monument's State of the Park report.