Methods of Evapotranspiration Estimation

Abstract

Contemporary methods of evapotranspiration estimation are described in detail, along with transpiration and evaporation. Measurement of evapotranspiration by lysimeters (from bare soil or soil with a canopy) and measurement of evaporation from a water table are described. A wide variety of evapotranspiration calculation systems are presented, starting with the soil water balance method. These include a group of micrometeorological techniques to which belong turbulent diffusion, energy balance, eddy correlation, and the so-called combination method, which combines water vapor and sensible heat transport equations and the energy balance equation at the evaporating surface. The Penman and Penman-Monteith approaches also belong to this group of procedures. Many empirical equations allow potential evapotranspiration calculation with limited data input. A method of tree transpiration estimation using sap flow measurement is described.