Even in the humid climate of Central Europe more than half of the precipitation is not leaving the river basins as discharge but is restored to the atmosphere by evapotranspiration. The importance of this component of the water balance for water resources, agriculture, forestry and ecology as well as the need for appropriate methods for the determination are evident. For an evaluation of methods presently in use in the Federal Republic of Germany more than 200 institutions and authorities with several hundreds of meteorological stations were questioned about their measuring installations, obtained data and applied methods to determine or estimate potential or actual evapotranspiration. Results are given in this report and on the attached map. It is an aim of this study to promote the exchange of experience and data.
