Runoff and soil erosion modeling by AnnAGNPS in a small Mediterranean watershed

In order to contribute to the study of hydrological processes and the evaluation of prediction models of runoff and sediment yield in a Mediterranean environment, an application of the distributed parameter, physically-based, continuous simulation, daily time step AnnAGNPS model has been performed, using a 9-years hydrological database collected at a Sicilian experimental watershed (130 ha) mainly pasture. The model showed a satisfactory capability in simulating surface runoff at daily, monthly and annual scale after a calibration process. Peak flow predictions were generally appreciable for low events and poor for higher flow rates. A high model efficiency was achieved for the 25 suspended sediment yield events recorded during the whole period of observation after reducing the roughness coefficients for both rangeland and cropland areas. The overall results confirmed the applicability of the AnnAGNPS model to the experimented conditions. Further improvements both in the hydrological submodel and in the erosion component could result in a higher reliability in the model predictions.