ET stands for evapotranspiration and is a measurement of the loss of moisture in the landscape through evaporation from the soil and transpiration from plant leaf surfaces.
It is an amount (inches per day) that is needed to irrigate to replace the moisture plants have lost.
ET is affected by:
- Length of daylight hours and intensity of sun (solar radiation)
- Temperature (higher temperature results in higher water loss)
- Wind (higher wind results in higher water loss)
- Humidity (lower humidity results in higher water loss)