Evapotranspiration Measurements and Calculations

Richard Allen, Thomas Foken, Ayse Kilic, Ricardo Trezza, Samuel Ortega-Farias

Research output: Chapter in Book/Report/Conference proceedingChapter

1 Scopus citations


Actual and maximum rates of evaporation (E) and evapotranspiration (ETevapotranspiration (ET)) are important to the operation of atmospheric process models and for hydrologic and agricultural modeling. Because rates of evapotranspiration are limited by both the available energy at the surface and the availability of water, a variety of techniques can be used for estimation. The near-maximum ET under nonlimiting water availability can be closely approximated by the reference ET concept using near-surface observations of air temperature, humidity, wind speed, and solar radiation via the Penman–Monteith or a similar method. The determination of actual rates of ET when water is limiting demands a more complex approach, and often requires daily (or even more frequent) water balance data for the upper soil layers. An alternative is to measure the actual ET using micrometeorological techniques such as the eddy-covariance and Bowen ratio methods. The application of standardized calculations for the reference ET is discussed, as are iterative surface energy balance–aerodynamic combinations, which are useful in conditions where water is limiting.

Original languageEnglish (US)
Title of host publicationSpringer Handbooks
PublisherSpringer Science and Business Media Deutschland GmbH
Number of pages37
StatePublished - 2021

Publication series

NameSpringer Handbooks
ISSN (Print)2522-8692
ISSN (Electronic)2522-8706


  • Bowen-ratio method
  • Class A pan
  • Penman–Monteith method
  • Priestley–Taylor method
  • crop coefficient
  • evaporation
  • evapotranspiration
  • latent heat flux
  • reference evapotranspiration method

ASJC Scopus subject areas

  • General


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