Comparison of Measured and WEPP Predicted Runoff and Sediment Loss from Deep Loess Soils Watershed

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