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Research Project: Technologies for Managing Water and Sediment Movement in Agricultural Watersheds

Location: Watershed Physical Processes Research

Title: Effectiveness of alternative management scenarios on the sediment load in a Mediterranean agricultural watershed

Author
item ABDELWAHAB, OSSAMA - Bari University
item Bingner, Ronald - Ron
item MILILLO, FABIO - Bari University
item GENTILE, FRANCESCO - Bari University

Submitted to: Journal of Agricultural Engineering Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/29/2014
Publication Date: 11/5/2014
Publication URL: http://handle.nal.usda.gov/10113/63312
Citation: Abdelwahab, O.M., Bingner, R.L., Milillo, F., Gentile, F. 2014. Effectiveness of alternative management scenarios on the sediment load in a Mediterranean agricultural watershed. Journal of Agricultural Engineering Research. 45(3):125-136.

Interpretive Summary: Evaluation and assessment of watershed agricultural management practices are critical in selecting 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 southern Italy experimental watershed for 2007-2011. The model predictions have proven to be good for runoff and sediment load and satisfactory for peak discharge. Implementation of alternative management practices demonstrated through the model simulations that by treating 13.5% of the most severe eroding areas with no tillage sediment load could be reduced by 30%, but treating those same areas with a grass cover could reduce sediment load by 36.5%. Implementing a crop rotation of wheat and a forage crop can reduce erosion by 69%. 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: The AnnAGNPS model was used to evaluate the effectiveness of different Management Practices (MPs) on soil erosion and sediment load in the Carapelle watershed, a Mediterranean medium-size watershed (506 km2) located in Apulia, Southern Italy. The model was previously calibrated and validated using five years of runoff and sediment load data measured at a monitoring station located at Ordona – Ponte dei Sauri Bridge. A total of 36 events were used to estimate the performance of the model during the period 2007-2011. The model performed well in predicting runoff, as was testified by the high values of the coefficients of efficiency and determination during the validation process. The peak flows predictions were satisfactory especially for the high flow events; the prediction capability of sediment load was good, even if a slight over-estimation was observed. Simulations of alternative management practices show that converting the most eroding cropland cells (13.5% of the catchment area) to no tillage would reduce soil erosion by 30%, while converting them to grass or forest would reduce soil erosion by 36.5% in both cases. A crop rotation of wheat and a forage crop can also provide an effective way for soil erosion control as it reduces erosion by 69%. Those results can provide a good comparative analysis for conservation planners to choose the best scenarios to be adopted in the watershed to achieve goals in terms of soil conservation and water quality.