The Annualized Agricultural Non-point Source (AnnAGNPS) model can be used to analyze the effects of management practices on sediment loads in agricultural watersheds. The study was performed in a 506 km2 Mediterranean watershed located in Apulia, Southern Italy, planted with mostly winter wheat (83%) where runoff and sediment loads have been monitored at an in-stream gage. The AnnAGNPS model was used to predict runoff and sediment load without calibration during a 5-year period. On an annual scale, the model showed good prediction capability for runoff (R2 = 0.8, NSE [Nash and Sutcliffe coefficient of efficiency] = 0.7) and satisfactory results for sediment load (NSE = 0.5, R2 = 0.5). Based on the current conditions of the watershed as a baseline scenario, the effectiveness of alternative conservation practices applied within the watershed was also evaluated. No-tillage practices applied to the entire cropland area reduced soil erosion within fields by 44% and sediment yield from fields to streams by 20%. Reduced tillage decreased soil erosion, sediment yield, and sediment load at the gage location by 12%, 7%, and 4% respectively. Limiting the placement of alternative practices to the cropland sub-watersheds with the most erosion (Scenarios G and H) proved to be a promising and viable approach to sediment erosion reduction throughout the watershed. In this perspective, areas that produce the most sediment were identified and targeted for replacement of varying levels of cropland with forest, and consequently sediment loads were reduced from 5% to 97%. The effect of vegetated streams and riparian buffers as natural traps that can increase the in situ sediment deposition was also considered. Most, but not all of the scenarios discussed herein could realistically be implemented within the watershed, particularly if there are incentive policies. Even considering the intrinsic uncertainty of modeling results, evaluating these systems with the aid of AnnAGNPS serves as a means to provide reference information and allows watershed conservation planners to compare the impacts of different management scenarios with sustainable agriculture guidelines.

Evaluation of Alternative Management Practices with the AnnAGNPS Model in the Carapelle Watershed

ABDELWAHAB, OSSAMA MOHAMED MAHMOUD;MILILLO, Fabio;GENTILE, Francesco
2016-01-01

Abstract

The Annualized Agricultural Non-point Source (AnnAGNPS) model can be used to analyze the effects of management practices on sediment loads in agricultural watersheds. The study was performed in a 506 km2 Mediterranean watershed located in Apulia, Southern Italy, planted with mostly winter wheat (83%) where runoff and sediment loads have been monitored at an in-stream gage. The AnnAGNPS model was used to predict runoff and sediment load without calibration during a 5-year period. On an annual scale, the model showed good prediction capability for runoff (R2 = 0.8, NSE [Nash and Sutcliffe coefficient of efficiency] = 0.7) and satisfactory results for sediment load (NSE = 0.5, R2 = 0.5). Based on the current conditions of the watershed as a baseline scenario, the effectiveness of alternative conservation practices applied within the watershed was also evaluated. No-tillage practices applied to the entire cropland area reduced soil erosion within fields by 44% and sediment yield from fields to streams by 20%. Reduced tillage decreased soil erosion, sediment yield, and sediment load at the gage location by 12%, 7%, and 4% respectively. Limiting the placement of alternative practices to the cropland sub-watersheds with the most erosion (Scenarios G and H) proved to be a promising and viable approach to sediment erosion reduction throughout the watershed. In this perspective, areas that produce the most sediment were identified and targeted for replacement of varying levels of cropland with forest, and consequently sediment loads were reduced from 5% to 97%. The effect of vegetated streams and riparian buffers as natural traps that can increase the in situ sediment deposition was also considered. Most, but not all of the scenarios discussed herein could realistically be implemented within the watershed, particularly if there are incentive policies. Even considering the intrinsic uncertainty of modeling results, evaluating these systems with the aid of AnnAGNPS serves as a means to provide reference information and allows watershed conservation planners to compare the impacts of different management scenarios with sustainable agriculture guidelines.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11586/181203
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