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Walnut Gulch Experimental Watershed, Kendall (Carbon Dioxide and Water Flux)

posted on 2023-11-30, 08:41 authored by William Emmerich

Atmospheric carbon dioxide and moisture concentrations were measured with an infrared gas analyzer (IRGA) (LI-6262, LI-COR, Inc. Lincoln, Nebraska, USA). Measurements were made from 1997 through the present at the Kendall site. The meteorological data and Bowen ratio energy balance systems (BREB) (Model 023/CO2 Campbell Scientific Inc., Logan, Utah, USA) data are used to calculate carbon dioxide and evapotranspiration (ET) fluxes. The stored Bowen ration instrument data from the measurement site were transmitted by radio daily to our research station in Tombstone, AZ. From there, they were transferred through an Internet connection to Tucson, AZ. The data were then divided into 5-day increments and inserted into a Quattro1 Pro spreadsheet file which had all the formulations to calculate flux of soil heat, latent heat, sensible heat, evapotranspiration rates (ET), and CO2 rates on the 20-min time step of the data. All instrument and calculated data were graphed in the spreadsheet file and thoroughly reviewed for any instrument problems or data stream collection issues. Carbon dioxide and water fluxes are important components of watershed function. In order to study carbon dioxide and water flux as they exist over the Walnut Gulch Experimental Watershed (WGEW), two sites were selected on the basis of their ecosystem composition, one site being dominated by shrubs and the other a grass dominated plant community. The grass site is identified as Kendall (109560800W, 314401000N; elevation; 1526 m). The soils at the Kendall site are a complex of Stronghold (coarse-loamy, mixed, thermic Ustollic Calciorthids), Elgin (fine, mixed, thermic, Ustollic Paleargids), and McAllister (fine-loamy, mixed, thermic, Ustollic Haplargids) soils, with Stronghold the dominant soil [NRCS Soil Survey, 2003]. Slopes range from 4 to 9%. The Stronghold surface A horizon (0-3 cm) contains 670 g kg1 sand, 160 g kg1 silt, and 170 g kg1 clay with 790 g kg1 coarse fragments >2 mm, 11 g kg1 organic carbon, and 7 g kg1 inorganic carbon. Vegetation is dominated by herbaceous plants, predominately black grama (Bouteloua eriopoda (Torr.) Torr.), sideoats grama (Bouteloua curtipendula (Michx.) Torr.), three-awn (Aristida sp.) and cane beardgrass (Bothriochloa barbinodis (Lag.) Herter). Vegetation canopy height at the grass site ranged from 0.4 to 0.7 m during the growing season.

Resources in this dataset:


Agricultural Research Service


Data contact name

Armendariz, Gerardo


U.S. Department of Agriculture - Agricultural Research Service

Intended use

The data set has been used for a wide variety of investigations into watershed properties and functions. For example, remote sensing data was used to calibrate an ecosystem model for semiarid perennial grasslands [Nouvellon et al., 2001]. Meteorological data from the data set, simulated plant growth, and water budget data from the data set drove the model.

Use limitations

Instrument data determined to be bad were kept in the set to preserve the measurements collected by the instrumentation. Depending on the length of time the instrument data were bad, the calculated values were estimated by linear interpolation. Linear interpolation was used for short time periods (up to 6 h) where it would be appropriate on the basis of similar meteorological conditions at the time. Bad calculated data based on bad instrument data for longer time periods were not estimated and left blank in the data set. For certain periods, usually at sunrise and sunset when Bowen ratio was near 1.0, calculated data were estimated by linear interpolation with less than 5% of the data interpreted in this way. Finally, all carbon dioxide and ET flux data were critically examined for unusual or unexplained values that were then linearly interpolated.

Temporal Extent Start Date



  • Not specified

Geographic Coverage


ISO Topic Category

  • environment
  • farming

Ag Data Commons Group

  • Walnut Gulch Experimental Watershed
  • Long-Term Agroecosystem Research

National Agricultural Library Thesaurus terms

carbon dioxide; meteorological data; models; evapotranspiration; radio; soil; heat; watersheds; ecosystems; shrubs; grasses; soil surveys; sand; silt; clay; carbon; vegetation; herbaceous plants; canopy; growing season; grasslands; plant growth; water balance

OMB Bureau Code

  • 005:18 - Agricultural Research Service

OMB Program Code

  • 005:040 - National Research

Pending citation

  • No

Public Access Level

  • Public

Preferred dataset citation

Emmerich, William (2020). Walnut Gulch Experimental Watershed, Kendall (Carbon Dioxide and Water Flux). U.S. Department of Agriculture - Agricultural Research Service.