Field scale estimation of evapotranspiration

Authors: MOORHEAD, JERRY

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 8/16/2018
Publication Date: 4/3/2019
Citation: Moorhead, J.E. 2019. Field scale estimation of evapotranspiration. In: Bucur, D., editor. Advanced Evapotranspiration Methods and Applications. London, United Kingdom: IntechOpen Limited. p. 1-19.
DOI: https://doi.org/10.5772/intechopen.80945

Interpretive Summary: Water is one of the most essential natural resources, especially for agriculture. In drier climates, tracking water in the soil is needed to ensure the best water management, especially for irrigation. The supplies are often determined from models. Most models use crop water use as an input, or as a check to verify the model outputs are good. These facts make knowing how much water crops in a field are using a necessity. In this chapter, current methods and tools are described. There are many methods today, and some are better than others, depending on how they are used.

Technical Abstract: Evapotranspiration (ET) is a major component of the water cycle, which makes it an integral part of water resources management, especially in arid and semi-arid environments. ET data are used for water management, irrigation scheduling, various modeling activities, and much more. Some areas of scarce water resources place limitations on water use, which are typically determined from various modeling approaches. As many models use ET as an input, or for validation, accurate ET data is essential to ensure accurate model outputs. In addition, most water management practices are done at the field scale, ET data of a similar scale is needed. Many ET measurement or estimation methods exist and vary widely in approach, instrumentation, complexity, and purpose. A lysimeter is considered the standard for ET measurement and is the most accurate. Other, more portable options are available, such as eddy covariance, scintillometers, Bowen Ratio, and remote sensing, all capable of estimating actual field ET within approximately 30% of actual values. Although other methods may not be as accurate as a lysimeter, each as benefits in certain situations. Depending on the purpose, that level of accuracy may be suitable. ET estimation methods are constantly evolving and accuracy should continually improve further.