Reference evaporation and its application in agrometeorology

Climate change places the agriculture in front of new challenges. An assessment of the water requirement of grassland, pasture and arable land on the basis of the evapotranspiration potential plays a central role in the planning of adaptation measures. The reference evaporation, a concept introduced in the 1990’s by the Food and Agriculture Organization (FAO) and presented in this paper, defines the evaporation potential of standard vegetation with an abundant water supply. It is determined on the basis of the so-called Penman-Monteith equation and, as demonstrated here, is able to accurately reproduce the evolution of the evaporative flux from grassland as observed on the Swiss Plateau under virtually optimum conditions.