The EarthWord: Evapotranspiration

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A Frankenword portmanteau of evaporation and transpiration that is used to account for all of the water that moves from the Earth’s surface to the atmosphere. Transpiration is the amount of water that leaves plants as water vapor through openings in the plant known as stomata, while evaporation is the conversion of water into water vapor.

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Water droplets on a leaf.
Water droplets on a leaf. Credit: Siddharth Patil. Available under the Creative Commons CC0 1.0 Universal Public Domain Dedication

Definition:

  • A Frankenword portmanteau of evaporation and transpiration that is used to account for all of the water that moves from the Earth’s surface to the atmosphere. Transpiration is the amount of water that leaves plants as water vapor through openings in the plant known as stomata, while evaporation is the conversion of water into water vapor.

Etymology:

  • This one has a fair amount of etymology in it, since it combines both evaporation and transpiration. We’ll start with evaporation, which comes to us from the Latin vapor, meaning “smoke” or “steam.” Transpiration itself is a compound word, including the Latin trans, which means “through,” and the Latin spirare, which means “to breath.”

Use/Significance in the Earth Science Community:

  • Evapotranspiration is an important aspect for water availability and ecosystem studies.

USGS Use:

  • USGS accounts for evapotranspiration in its annual water use reports and in water availability studies such as the USGS Water Census project. Evapotranspiration is also an important aspect of climate and land use change research at USGS. Different ecosystems, like forests vs. deserts, as well as different land uses, such as farming vs. urban, have different rates of evapotranspiration.
  • Evapotranspiration is also an important aspect of climate and land use change research at USGS. Different ecosystems, like forests vs. deserts, as well as different land uses, like farming vs. ranching vs. urban development, have different rates of evapotranspiration, and a changing climate is likely to affect those rates.

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