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Title: APPLICATION OF ANNAGNPS MODEL AS A LANDUSE MANAGEMENT TOOL IN NAVARRE

Author
item GASTESI, RAKEL - PUBLIC UNIV OF NAVARRE
item CASALI, J. - PUBLIC UNIV OF NAVARRE
item THEURER, FRED - USDA, NRCS
item Bingner, Ronald - Ron
item RECASENS, S. - PUBLIC UNIV OF NAVARRE
item DE SANTISTEBAN, L. - PUBLIC UNIV OF NAVARRE
item BANDRES, B. - PUBLIC UNIV OF NAVARRE

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 8/1/2006
Publication Date: 9/1/2006
Citation: Gastesi, R., Casali, J., Theurer, F.D., Bingner, R.L., Recasens, S., De Santisteban, L., Bandres, B. 2006. Application of AnnAGNPS Model as a Landuse Management Tool in Navarre. In: Proceedings of the International ESSC Conference on Soil and Water Conservation Under Changing Land Use, September 12-15, 2006. Catalonia, Spain. 2006 CDROM.

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 two agricultural watersheds in the Navarre region of Spain for 1996-2005. The model represented the overall runoff and sediment yield for the period very well, within 7% and 9% of observed, respectively. Individual simulated events and monthly summaries produced results that contained more variation when compared to observed, but the simulations were performed without calibration and thus, could be improved with further study. Simulation scenarios were applied where the watersheds were evaluated as if the watershed contained all forested or fallow conditions. The model represented the forest conditions with a significant decrease in runoff and sediment yield while the fallow conditions produced a slight increase in results compared to the existing conditions of cereal grain crops. The representation of the observed trends provides insight in the capability of the model to represent non-U.S. watersheds and may lead to needed improvements in the data that is available in Spain for the model. 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 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: The objective of this study was to analyze the performance of AnnAGNPS by comparing the modeling of the actual land use conditions with the monitoring dataset at the two watersheds of Navarre. Secondly, the model was used to simulate the runoff and sediment losses in a different set of scenarios, regarding land use and agricultural management practices as hypothetical situations in both watersheds. The model output for the actual landuse conditions were compared with the observed data for the 1996-2005 period. All these simulations were done prior to calibration. The comparison of observed and simulated runoff totals throughout the simulation period yielded an error of -7%. Regarding sediment totals this error was -9%. However the yearly simulation gave overestimation in some years and underestimation in others for runoff, and more markedly that of the sediment yield. Spatial distributed output results were also obtained.