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Ag Water Conservation Policy

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https://hdl.handle.net/10217/195471

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Browsing Ag Water Conservation Policy by Author "Andales, Allan A., author"

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    ItemOpen Access
    Mapping ET in southeastern Colorado using a surface aerodynamic temperature model
    (Colorado State University. Libraries, 2010) Chávez, José L., author; Straw, Dale, author; Garcia, Luis A., author; Ley, Thomas W., author; Andales, Allan A., author; Simmons, Lane H., author; U.S. Committee on Irrigation and Drainage, publisher
    Accurate estimates of spatially distributed evapotranspiration (ET) using remote sensing inputs could help improve crop water management, the assessment of regional drought conditions, irrigation efficiency, ground water depletion, and the verification of the use of water rights over large irrigated areas. In this study, ET was mapped using surface reflectance and radiometric temperature images from the Landsat 5 satellite in a surface energy budget algorithm driven by a surface aerodynamic temperature (SAT_ET) model. The SAT_ET model was developed using surface temperature, horizontal wind speed, air temperature and crop biophysical characteristic measured over an irrigated alfalfa field in Southeastern Colorado. Estimates of the remote sensing-based ET for a 4.0 hectare alfalfa field and a 3.5 hectare oats field, during the 2009 cropping season, were evaluated using two monolithic weighing lysimeters located at the Colorado State University Arkansas Valley Research Center (AVRC) in Rocky Ford, Colorado. Although the overall model performance was encouraging, results indicated that the SAT_ET model performed well under dry atmospheric and soil conditions and less accurately under high air relative humidity and soil water content conditions. These findings are evidence that SAT_ET needs to be further developed to perform better under a range of environmental and atmospheric conditions.
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    ItemOpen Access
    Performance evaluation of TDT soil water content and watermark soil water potential sensors
    (Colorado State University. Libraries, 2011-04) Varble, Jordan L., author; Chávez, José L., author; Andales, Allan A., author; Butters, Greg L., author; Trout, Thomas J., author; U.S. Committee on Irrigation and Drainage, publisher
    This study evaluated the performance of digitized Time Domain Transmissometry (TDT) soil water content sensors (Acclima, Inc., Meridian, ID) and resistance-based soil water potential sensors (Watermark 200, Irrometer Company, Inc., Riverside, CA) in two soils. The evaluation was performed by comparing volumetric water content (θv) data collected in the laboratory and in fields near Greeley, CO, with values measured by the sensors. Calibration equations of θv were then developed based on the laboratory and field data. Statistical targets to determine accuracy of the equations were ±0.015 m³ m⁻³ mean bias error and a root mean square error of less than 0.020 m³ m⁻³. Under laboratory and field conditions, the factory-based calibrations of θv did not consistently achieve the required accuracy for either sensor. Field tests indicated that using the calibration equation developed in the laboratory to correct data obtained by TDT and Watermark sensors in the field at Site A (sandy clay loam) was not consistently accurate. Using the laboratory equations developed for the Watermark sensors at Site B (loamy sand) accurately measured θv. Field tests found that a linear calibration of the TDT sensors (and a logarithmic calibration for the Watermark sensors) could accurately correct the factory calibration of θv in the range of permanent wilting point (PWP) to field capacity (FC). Furthermore, the van Genuchten (1980) equation was not significantly more accurate than the logarithmic equation, and the additional work of deriving the former equation did not seem worthwhile, within the range of soil water contents analyzed.