What is Evapotranspiration (ET)?

Overview

Weather-based irrigation controllers use real-time weather data to schedule irrigation based on local evapotranspiration (ET.) ET is defined as the quantity of moisture that is both transpired by the plant (i.e., the water vapor released from its leaves) and evaporated from the soil and plant surfaces. As demonstrated in the figure below, ET is a function of weather conditions and plant type.