Hydro-pedotransfer functions for predicting the effective annual capillary rise

New hydro-pedotransfer functions for grassland are presented to calculate both annual capillary rise from the groundwater into the root zone and actual evapotranspiration for regional water balances. The functions i.e. the procedure has two advantages. Firstly, only easily available site information is necessary for the calculation, such as the soil texture class, groundwater depth, summer rainfall and potential evapotranspiration (ETpot ) according the FAO guideline. Secondly, we follow the principle idea to define the gain (G) of actual evapotranspiration (ET act ) caused by capillary rise from groundwater as an effective parameter to express both, the soil and climate dependent effective capillary rise for a given site. In order to define a reference, we used the actual evapotranspiration of a site without groundwater influence but with same soil hydraulic properties and climate conditions. In order to predict G without using the numerical model, a new hydro-pedotransfer concept was developed and tested for several regions in Germany, Europe.