evapotranspiratie

Evapotranspiration, known in Dutch as evapotranspiratie, is the process by which water is transferred from the land surface to the atmosphere through evaporation from soil and water surfaces and transpiration from vegetation. It represents a major component of the hydrological cycle and links soil moisture, plant physiology, and atmospheric demand. The amount of ET varies with weather, soil moisture, and vegetation characteristics.

ET is driven by meteorological factors such as solar radiation, air temperature, relative humidity, and wind speed, as well as by soil moisture and plant type. When soil moisture is sufficient, transpiration from leaves is often the dominant pathway; during drought or soil drying, evaporation from the surface declines and plant stomata may close, reducing ET. Vegetation type, canopy structure, and rooting depth also influence ET through differences in stomatal behavior and access to water.

Measurement and estimation of ET employ several approaches. Direct methods include lysimeters, which weigh or measure water balance to determine losses, and eddy covariance, which assesses turbulent fluxes between surface and atmosphere. Sap-flow techniques estimate transpiration in plants. For larger-scale assessments, remote sensing and surface-energy balance models are used, along with water balance approaches. A common reference framework is the FAO-56 Penman-Monteith method to estimate reference evapotranspiration (ET0), with crop-specific coefficients adjusting ET0 to actual crop evapotranspiration (ETc).

Applications of evapotranspiratie include irrigation scheduling, water resources management, drought assessment, and climate research. Understanding ET supports efficient water use in agriculture and informs hydrological and climate models by integrating atmospheric demand with soil and vegetation conditions.