Date of Award:

8-2024

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Civil and Environmental Engineering

Committee Chair(s)

J. Burdette Barker

Committee

J. Burdette Barker

Committee

Lawrence Hipps

Committee

Alfonso Torres-Rua

Abstract

Evapotranspiration, the combined movement of water from the earth's surface and plants to the atmosphere, is a component of the energy balance of the land surface atmosphere continuum. Often, irrigation is used to replace water removed from the soil through evapotranspiration. Water management for irrigation is often done at the plot or field scale. Due to the smaller footprint size and the large upfront costs, evaluating evapotranspiration at such a small scale can be difficult to justify. The aim of the study was to quantify evapotranspiration at the plot scale. An energy balance model that evaluates energy from two sources, the soil surface and the vegetation surface, was used to model the energy balance in an alfalfa-grass mix field in Northeastern Utah. Two canopy sensor stations used to collect data for this model were deployed throughout the growing seasons of 2022 and 2023. The stations were in proximity to an eddy covariance tower. The eddy covariance method is widely regarded as one of the best ways to sense actual, not modeled, evapotranspiration. The canopy sensing stations’ energy fluxes were compared against the eddy covariance tower. During 2022, canopy Stations 1 and 2 were stationary. During 2023, Station 1 remained stationary, while Station 2 was moved around throughout the season. Some properties of the vegetation canopy were needed for the two-source model. Those primarily include fraction of vegetative cover, leaf area index, and crop height. These represent the percentage of viewing area that is covered by vegetation, the ratio of plant leaf area to ground area, and the height from the soil surface of the crop. These vi properties were modeled with success from various methods. The model produced estimates of all four components of the energy balance, net radiation, sensible heat flux, soil heat flux, and latent heat flux (which is energy used in evapotranspiration). These components were then compared against the eddy covariance tower components. Latent heat fluxes were converted into evapotranspiration rates. Results were mixed. Stations were operated and continuously collected plot-scale data. Station evapotranspiration responded well to seasonal changes. However, station evapotranspiration was biased high through the entire growing season.

Checksum

9448a14f7694b26e0493e4a7a73b346b

Download

Share

COinS

Copyright for this work is retained by the student. If you have any questions regarding the inclusion of this work in the Digital Commons, please email us at .