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U.S. GEOLOGICAL SURVEY
Data Series 284

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Summary

Micrometeorological and soil-moisture data were collected at the Amargosa Desert Research Site facility adjacent to a low-level radioactive and hazardous-chemical waste facility near Beatty, Nevada, 2001–05. Evapotranspiration (ET) data were collected from February 14, 2002, through December 31, 2005. Data were collected in support of ongoing research to improve the understanding of hydrologic and contaminant-transport processes in arid environments.

Micrometeorological data include solar radiation, net radiation, air temperature, relative humidity, saturated and ambient vapor pressure, wind speed and direction, barometric pressure, precipitation, and near-surface soil temperature, soil-heat flux, and soil-water content. All micrometeorological data were col­lected using a 10-second sampling interval by data log­gers that output daily and hourly mean values. Daily maximum and minimum values are based on hourly mean values. Precipitation data output included daily and hourly totals. Selected soil-moisture profiles at depth include periodic measure­ments of soil volumetric water-content measurements at nine neutron-probe access tubes to depths ranging from 5.25 to 29.25 m. ET data include measurements of daily ET and 15-minute fluxes of the four principal energy budget components of latent-heat flux, sensible-heat flux, soil-heat flux, and net radiation. Time-series data are plotted to illustrate temporal variations in micrometeorological, soil-water content, and ET data.

Total annual precipitation for 2001–05 averaged 130.3 mm with measured totals of 164.8 mm in 2001, 3.5 mm in 2002, 131.8 mm in 2003, 173.6 mm in 2004, and 177.7 mm in 2005. The 25-year (1981–2005) long-term average annual precipitation averaged 112 mm at the ADRS. The low annual precipitation in 2002 was associated with a La Niña event along the eastern Pacific Ocean. After significant winter rains that totaled 217 mm from October 2004 through February 2005, changes in soil moisture were recorded in early August 2005 to a depth of at least 2.75 m at the devegetated native-soil site and 1.25 m at the vegetated native-soil site. This is the deepest downward percolation of soil moisture documented at ADRS since investigations began in 1983. Recorded annual ET was 48 mm (based on 321 days) for 2002, 148 mm for 2003, 198 mm for 2004, and 233 mm for 2005.

ET consumes available moisture from plants and soil, and depends on precipitation to replace depleted soil moisture in this desert environment. During drought conditions, with maximum available energy during the summer months of 2002, daily ET typically was less than 0.2 mm/d. With less energy available during drought conditions in late autumn 2002, daily ET was estimated at less than 0.05 mm/d indicating a lower base discharge, although these values are within the measurement error. In contrast to 2002 (fig. 20), with an average daily ET of 0.15 mm/d for the period of record, ET in 2003–05 averaged about 0.5 mm/d. With precipitation to infiltrate soils, daily ET abruptly increased to as much as several millimeters per day and quickly decreased over several days or weeks, but maintained higher base levels of water discharge for extended periods after a storm event. Annual ET during 2003–05 exceeded precipitation measured at the site. ET in excess of precipitation may be attributed to some combination of long-term upward-moving soil moisture from depth, additional moisture inputs from dew formation and advection of unrecorded precipitation-derived moisture near the site, and measurement uncertainties.

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