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Non point source pollution and runoff simulation with AnnAGNPS model in a small irrigated watershed in Portugal
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Abstract(s)
The main objective of this study was the application of the hydrologic, non point source pollution model AnnAGNPS to a small watershed (189 ha) that has irrigated agriculture as major use. The study watershed is
located in the Idanha Irrigation Scheme (Portugal). The main irrigated crops are barley, corn and sorghum. Oat are cultivated rainfed and a young non-irrigated oak forest occupies one third of the watershed. Climate is
Mediterranean; topography slightly sloppy; the natural drainage network is dense; and the soils are heterogeneous with an impermeable layer at depth varying between 0.35 and 0.45 m. We measured runoff at the outlet of the watershed in a long-throated flume were water depth was recorded continuously. Water samples were collected almost daily for determining sediment and nitrogen concentrations. The study was carried out during the hydrologic years 2004/2005 and 2005/2006, including periods in which rain or irrigation were the dominant water precipitation sources. AnnAGNPS simulated runoff reasonably well. The main trends in sediment transport were captured by the model well. However, our analysis pointed to poor simulation of the nitrogen fate in the study environment, although we could not draw definitive conclusions because the sampling method of the observed data was not completely satisfactory. The spatial distribution of runoff and soil losses indicated where in the watershed especial care is needed for assuring sustainable management at the watershed scale.
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Citation
DUARTE, A.C. ; MATEOS, Luciano ; FERERES, E. (2007) - Non point source pollution and runoff simulation with AnnAGNPS model in a small irrigated watershed in Portugal. In 5th International Congress of the European Society for Soil Conservation, Palermo 2007 - Proceedings.