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Title: RUNOFF AND EROSION MODELING BY WEPP IN AN EXPERIMENTAL MEDITERRANEAN WATERSHED 1828

Author
item LICCIARDELLO, F. - UNIV. OF CATANIA-ITALY
item AMORE, E. - UNIV. OF CATANIA-ITALY
item Newell, Kelly
item ZIMBONE, S. - UNIV. REGGIO CALABRIA

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 3/1/2006
Publication Date: 5/1/2006
Citation: Licciardello, F., Amore, E., Newell, K.R., Zimbone, S.M. 2006. Runoff and erosion modeling by wepp in an experimental mediterranean watershed. In: Phillip Owens editors. Soil Erosion and Sediemnt Redistribution in River Catchments. CABI Publishing. p.186-394.

Interpretive Summary: Regulatory policy and land management approaches include the use of soil erosion models to provide the information on natural hazards and human impacts to support soil conservation planning, both through agricultural legislation that defines maximum tolerable soil loss rates, and through federal and local legislation that requires soil erosion controls on many construction sites. To be useful for decision makers, soil erosion models must have simple data requirements and must be applicable to a variety of regions with minimum calibration. In this syudy the results of applications of the Water Erosion Prediction Project (WEPP) model to monitored watersheds were analysed in order to draw conclusions on model implementation and performance in semi-arid regions of Sicily. The results of the study showed that the modfel could be calibrated in such a way as to be effecitve for this region. This has important implications in that it shows that erosion models may be effecitvely applied in semi-arid environments for the purposes of helping to make land management and engineering decisions.

Technical Abstract: In recent decades several simulation models have been developed to estimate and analyse the impact of water erosion at watershed scales, but more work is needed to test and improve their applicability and efficiency in environmental situations that differ from those where the models were developed. The Water Erosion Prediction Project (WEPP) is a physically based, distributed parameter model that has been widely applied around the world to simulate the main physical processes related to infiltration, percolation, runoff, and soil erosion phenomena at hillslope and watershed scales. In this paper the results of applications of WEPP to the monitored watershed model were analysed in order to draw conclusions on model implementation and performance in the experimental conditions studied. Storm runoff depth was generally underestimated for both large and small rainfall events. The annual runoff depth was underestimated for three of the six years. The results suggested possibilities of improvement for the WEPP and GeoWEPP models. The definition of excessively long slope lengths by GeoWEPP needs to be corrected, or alternatively, some modification of the WEPP model is needed to prevent the over-prediction of erosion rates from these long slopes. Secondly, in semi-arid conditions such as those in this study, spatial variability in rainfall is an important problem that cannot be represented in WEPP. In spite of the difficulties encountered and the limitations of the model, and given the relatively low rates of erosion, the results were quite reasonable.