Climate, Springs and the West Fork Gila River at Gila Cliff Dwellings, Water Year 2019

Measuring streamflow on the West Fork Gila River. Image from the NPS's page.

Why climate and water are monitored together

Climate and water shape how ecosystems work, especially in dry country, and changes in climate, groundwater and surface water affect a park's plants, animals and often its cultural resources. At Gila Cliff Dwellings National Monument in New Mexico, the Park Service's Sonoran Desert Network measures climate, springs and streams year after year — like a doctor tracking a patient's vital signs — to give early warning of problems. Results are reported by water year, running from October to the following September; water year 2019 ran from October 2018 to September 2019.

Climate

Weather is the conditions at a moment; climate is the pattern of weather at a place over seasons to years, and it drives ecological processes. By an aridity index — long-term precipitation compared with potential evaporation — Gila Cliff Dwellings is semi-arid.

Aridity index versus elevation for selected national parks. NPS figure.

Data come from a National Oceanic and Atmospheric Administration cooperative weather station at Gila Hot Springs, running since 1957, and a Remote Automated Weather Station at the monument since 1998, both on the Climate Analyzer.

• Precipitation: 16.6 inches (42.2 cm), 0.37 inches above the 1981–2010 normal. Heavy rain (more than 1 inch) fell on 2 days — normal — including 1.12 inches on July 7 and 1.53 inches on August 4.
• Temperature: the year's average was within 1°F of normal, but summer highs ran hot from June to September. August's average high, 91.6°F (33.1°C), was 7.1°F above normal, and very hot days (above 92.0°F) came on 37 days — 2.5 times the normal number.
• Drought: the reconnaissance drought index, comparing precipitation with evaporative demand, showed an average year.

Climate at Gila Hot Springs, water year 2019. Graphics generated by climateanalyzer.org.

Springs

Springs, seeps and tinajas are small, rare biodiversity hotspots in dry lands, linking groundwater to the surface. The key questions are how long a spring holds water and how much. Crews describe each spring, rate disturbance from 1 (undisturbed) to 4 (highly disturbed), note wetland plants, invasive plants, crayfish and bullfrogs, measure flow and extent, use temperature sensors to tell whether water was present, and test water quality.

Cliff Dweller Canyon Spring below its source, May 2019. Image from the NPS's page.

Hubbard's Bog. Image from the NPS's page.

The West Fork Gila River

The West Fork Gila River. Image from the NPS's page.

Streams and their riparian zones supply food, cover and water, serve as wildlife corridors, filter pollution, reduce erosion and floods, and recharge groundwater — yet riparian forests are among the country's most endangered. The West Fork Gila River crosses the monument's northeast corner, in the Gila Wilderness, with almost no upstream land use.

• Stresses: since 2001, drought has cut flow, and the river sometimes runs dry near the eastern boundary. Canyon walls squeeze floods: in 2008, a rain-on-snow flood carved a new channel and washed out campsites and a bridge. The 2011 Miller Fire and the 2012 Whitewater–Baldy Fire degraded aquatic habitat, helped exotic plants spread, and raised the risk of future flooding.
• Monitoring: water quality and flow at an index site, aquatic macroinvertebrates and habitat along a 570-meter reach, and every five years the channel shape and streamside vegetation; fish surveys come from other agencies.

Sampling locations on the West Fork Gila River. NPS map.

Water year 2019 results:

• Water quality: four sampling visits; of 243 analyses, 89 had state standards, and just one exceeded them — total aluminum in winter, at 3.4 mg/L against a calculated standard of 0.23 for aquatic life — a 99% compliance rate. During the fourth-quarter continuous monitoring, 3% of 1,818 readings fell below the 6 mg/L dissolved-oxygen standard, during short spells (under 4 hours) when the water warmed above 23°C. Nutrients, bacteria including E. coli, and sediment raised no concerns. (The logging instrument wasn't deployed in the second quarter, for fear of ice damage.)
• Flow: a hydrograph typical of the Upper Gila Basin, peaking with snowmelt from late February to early April; the biggest flow was 754 cubic feet per second on March 13, 2019. Mean flow was 34.76 and median 11.0 cubic feet per second.

Daily discharge, water year 2019. NPS figure.

• Aquatic macroinvertebrates: sampled on October 17, 2018, the New Mexico Stream Condition Index scored 48.37 — "fair," mid-range for high-elevation small watersheds.

Stream Condition Index scores, water years 2012–2019. NPS figure.

Sources

Based on "Climate and Water Monitoring at Gila Cliff Dwellings National Monument, Water Year 2019," Sonoran Desert Network, National Park Service; a work of the United States government in the public domain. One sentence of the source puts the aluminum exceedance in the third quarter; its results table and metals summary put it in winter, which this page follows.