Comparison of measured and WEPP predicted runoff and sediment loss from deep loess soils watershed

The Water Erosion Prediction Project (WEPP) watershed model (vets 99.5) is used to predict erosion on the hillslope portion of the watershed and sediment detachment, transport., and deposition in the channel system. In this study, the runoff and sediment loss prediction of the model was evaluated using measured data from a 6-ha watershed under continuous conventional corn located near Treynor, IA. The differences between the measured and predicted mean annual surface runoff and sediment loss were 10 and 45%, respectively. Most of the sediment delivery to the watershed outlet was contributed from the channels, indicating that ephemeral gully erosion was more serious than hillslope soil erosion. Overall, runoff prediction of the model was satisfactory. However, the model greatly overpredicted sediment loss, particularly for the events where no or small sediment loss was measured.