Comparison of wind erosion measurements in Germany with simulated soil losses by WEPS

The Wind Erosion Prediction System (WEPS) is a process-based model that simulates daily weather and field conditions along with hourly wind speeds and erosion. Its physical basis should allow model application to regions outside the US for which it was originally developed. The objective of this study was to compare results from measured wind erosion with simulated soil losses as a first example of WEPS use in Germany. Another objective was to introduce methods and techniques for quantifying wind erosion in preparation for model comparison studies to be undertaken within the Global Change and Terrestrial Ecosystems Soil Erosion Network. Comparisons between the measured and simulated erosion were based on single erosion events and outputs from the erosion submodel of WEPS. Multiple runs of the model were performed with varying roughness parameters to set the simulated threshold wind speed equal to that measured during the first erosion event after a tillage operation. This initial data set was used, depending on the rainfall or erosion, as the basis for the gradually changing roughness, crust cover and the fraction of erodible material on crust for all the following erosion events. Thus, the accuracy of the simulation depends much more on the relationship between erosion events, than on a good agreement for one single event. The results showed excellent agreement between measured and simulated erosion (R2 0.9). This is mainly attributed to the good agreement with the four largest erosion events in which transport exceeded 100 kg/m width. Excluding these events, R2 was reduced to about 0.6 for all other erosion events. Spatial and temporal variability of the soil transport were also reasonably simulated.