|The detailed determination of the soil water budget parameters is the basic prerequisite for authentic quantification of ecologically relevant information regarding water and substance fluxes in floodplains. A weighable lysimeter with automatically groundwater level regulation was developed and applied to determine the soil-water balance components precipitation, evapotranspiration, groundwater recharge, capillary rise and interaction with the surface water of these wet land sites. In contrast to calculation approaches described in literature the lysimeter investigations proved a distinct groundwater recharge for selected periods. Based on the lysimeter data the water balance was inversely modelled by applying the physically based model HYDRUS 1-D. These simulations are an essential precondition for further investigations on the matter budget of larger floodplain landscape units of the middle reaches of the Elbe River.