Automated classification of the German soil map (BUEK 200) into FOOTPRINT soil types and its parameterization for hydrological modelling

The FOOTPRINT Soil Type (FST) system has been derived during the FOOTPRINT project (2006-2009) to facilitate spatially distributed hydrological and solute transport modelling at national or EU scale. The basic idea of this approach is to classify the soil typological units (STUs) of a national or European soil database into a limited number of soil types (FSTs) in order to reduce the number of unique soil-climate combinations for the later numerically expensive simulations. The FST code consists of a hydrological class (the FOOTPRINT Hydrologic Group), a topsoil and a subsoil texture code and an organic matter profile code. The FST system is model-independent, but complete parameterization methodologies were established during FOOTPRINT for MACRO, a 1-D dual permeability model for simulating water flow and solute transport in macroporous soils at field level. In this study we i) translated the latest version of the German soil map 1:200,000 (BUEK200) into FSTs, ii) derived representative profiles for all FSTs with arable land use, and iii) parameterized these representative profiles in MACRO. The 3648 STUs with arable land use in the BUEK200 were classified into 226 FSTs. Area proportions covered by the different FSTs are highly skewed: The 13 FSTs with the largest areas already cover 50 % of the total arable land. The hydrological class of each FST indicates whether artificial drainage is needed to allow arable landuse, and a map of potentially drained arable land was derived for Germany accordingly. A representative soil profile was established for every FST by depth-based averaging over all soil profiles belonging to the same FST. Special care had to be taken to ensure that mineral soil layers were not mixed with peat or hard rock layers. The plausibility of the representative FST profiles and their MACRO parameterization was checked with water balance simulations. The present case study for the BUEK200 soil database demonstrates the potential of the FST system for spatially distributed hydrological and solute transport modelling at large scale based on national soil databases.