Analysing and modelling solute and sediment transport in the catchment of the Wahnbach River

A concept for the continuous modelling of erosion, solute and sediment transport at the catchment scale is presented. The simulation is based on the application of the OPUS model designed for single slopes. In order to apply the model at the catchment scale, the study area (54 km(2)) is discretized into numerous slopes. The simulation results are compared with measurements at different spatial and temporal scales of a mesoscale catchment used for drinking water supply. Three small sub-catchments, ranging between 21 and 29 ha, are used to validate the model at the local scale. Process observations at this scale are used to modify the OPUS model. While for the validation of the long-term water and solute transport daily measurements at the catchment outlet were available and used, the long-term simulation of the sediment transport is validated by analysing the sediments trapped in the drinking water reservoir. The results suggest that the model concept is applicable to a large range of scales from single events to decades and from single slopes to mesoscale catchments. However, the quality of the simulation depends on the kind of process considered. Best model results are achieved with the simulation of runoff and nitrate discharge, whereas the simulation of sediment transport is less satisfying. (C) 2003 Elsevier Science Ltd. All rights reserved.