ARS | Publication request: Runoff and Soil Erosion Evaluation by the AnnAGNPS Model

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 15, 2007
Publication Date: October 11, 2007
Citation: Licciardello, F., Zema, D.A., Zimbone, S.M., Bingner, R.L. 2007. Runoff and Soil Erosion Evaluation by the AnnAGNPS Model in a Small Mediterranean Watershed. Transactions of the ASABE, Vol. 50(5): 1585-1593.

Interpretive Summary: Evaluation and assessment of watershed agricultural management practices are critical in applying the best practices possible to control erosion and improve the downstream water quality. Watershed models have been extensively used within the U.S. for this purpose, but evaluations outside of the U.S. have been limited. An evaluation of the USDA watershed model AnnAGNPS was performed within a Sicilian experimental watershed representing Mediterranean conditions for 1997-2003. Calibration and validation were performed for separate three year periods. The model represented the runoff and sediment at individual event, monthly and annual time scales very well. Peak runoff rates predicted were generally good for low flow events and poorer for higher flow rates. The soil erosion estimates were very sensitive to the roughness parameter selected for rangelands and croplands. Understanding how the model performs under unique conditions with agricultural practices that are not common in the U.S. can provide insight into enhancements that may be needed to improve the model. These model assessments are critical since they are often the only means to evaluate the effects of conservation practices on water quality within a watershed.

Technical Abstract: 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-year hydrological database collected at a mainly pasture Sicilian experimental watershed (130 ha). The model showed satisfactory capability in simulating surface runoff at event, monthly and annual scale after calibration. Peak flow predictions were generally good for low flow events and poorer for higher flow rates. A high model efficiency was achieved for the 24 suspended sediment yield events recorded during the entire 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 experimental conditions. Further improvements, both in the hydrological and erosion components, could result in a higher reliability in the model predictions.