## 3 Results and Discussion  
The modelled soil erosion using the three different USLE approaches in all three test catchments resulted in substantially different overall erosion (Figure 2) and field-specific erosion patterns (Figure 3; Figure 4) between the different methods, while the mean erosion (over all methods) between the test catchments show substantial, but smaller differences (mean BY, AT, and CZ: 13.2, 17.7, and 10.4 h\({}^{-1}\) a\({}^{-1}\), respectively). The highest erosion rates at the Austrian site mostly result from the large proportion of row crops (45.6%), especially maize, without specific soil conservation measures (Table 1). Figure 3: Modelled mean erosion per parcel for the three test catchments in Czech Republic, Bavaria, and Austria using the different standard methods applied in the respective environmental administration. Moreover, the field means based on the EU map [19] are given in the right column. Figure 2: Boxplots of variability in soil loss based on data aggregated to parcels/fields; boxes indicate median and 25% and 75% quantiles, while whiskers give 5% and 95% quantiles. In general, the lowest modelled mean erosion for all catchments can be found applying the Bavarian method, followed by the Czech and Austrian approaches (Figure 2 and Table 3). The modelled mean erosion over all agriculturally used raster cells in the different catchments using the BY approach was 54% and 59% smaller than CZ and the AT approaches, respectively. While there is no systematic effect of field size on modelled erosion at the BY and AT test catchments (Figure 4F,K), which are characterized by a large number of relatively small fields (Table 1), there is a tendency that erosion at the CZ site increases with increasing field size (Figure 4C). In the Czech catchment, the BY method shows a systematic bias in field-specific erosion compared to the CZ methods. Relative differences in field-specific erosion between these methods increase with field size (Figure 4B). In contrast, no clear effect of field size and/or field erosion could be identified comparing the AT with the CZ method (Figure 4C). In the Bavarian catchment, more pronounced relative differences in field-specific erosion between the CZ and AT method as compared to the BY method were found (Figure 4E,G). With the CZ method, the largest relative deviations from the BY method were identified for small fields (Figure 4E), while for the somewhat larger fields, there is a more or less constant relative difference. Interestingly, relative differences in field erosion between the AT and the BY method indicate much more field specific variability (Figure 4G). Figure 4: Relative difference between field erosion modelled with different methods (and EU map [19]) and the method potentially best representing the catchment (e.g., in the CZ catchment: Czech (**A**), Bavarian (**B**), Austrian methods (**C**), and European map (**D**) vs. CZ method). Each data point represents the mean soil loss of a field. In the Austrian catchment, the largest relative differences between the CZ and BY vs. AT method occurred for small fields with low erosion (approx. \(<\) 2 t ha\({}^{-1}\) a\({}^{-1}\); Figure 4I,J). It is interesting to note that the difference in site-specific mean/median erosion (Figure 2; Table 2) as well as the relative difference (Figure 4G,J) between BY and AT methods are much smaller in case of the AT catchment compared to the BY catchment. It is obvious from the results shown above that even if all regional/national erosion approaches in principal use USLE-based technology [16], the regional adaptation of the model (as done for Bavaria by [PERSON] et al. [12]), the specific parameterization and technique to derive individual USLE factors, and the differences in available data, result in substantial differences in model results. We identified some bias between the mean field erosion resulting from the different methods but, moreover, found large differences in modelled erosion of individual fields.