Evapotranspiration

Evapotranspiration (ET) is the combined transfer of water from land to atmosphere through direct evaporation and plant transpiration. It is one of the main outgoing terms in the water balance and a key link between climate, vegetation, and water availability.

Components

• Evaporation from soil, open water, intercepted rain, and wet surfaces
• Transpiration from plants as water moves through vegetation and is released through stomata

Why it matters

Evapotranspiration determines how much incoming water remains available for runoff, recharge, and ecosystem storage. It also links water and energy exchange, because evaporation and transpiration consume energy and cool surfaces.

Main controls

• available energy and net radiation
• air temperature, humidity, and wind
• soil moisture and root-zone water availability
• vegetation type, density, and phenology

In hydroclimate

In hydroclimate studies, ET is important because wet and dry conditions are shaped not only by how much water arrives, but also by how quickly water is returned to the atmosphere. Actual evapotranspiration can differ strongly from potential demand when soils are dry or vegetation is stressed.

In this garden

This note mainly supports the hydroclimate and water balance branch of the garden. It is especially relevant when interpreting climate-model output in regions where direct hydrological observations are sparse.

See also: Water balance, Hydroclimate, Precipitation