**2. Aim of the work**

AnnAGNPS has been implemented to assess runoff water amount and quality as well as sediment yield in small to large monitored watersheds (ranging from 0.32 to 2500 km2

under different environmental conditions. Such applications were frequently coupled with calibration/validation trials. Poor AnnAGNPS predictions of sediment and nutrient loads were achieved in a Georgia watershed, covered by both extensive forest and riparian con‐ ditions and attributed this to the defective data input used with the model (Suttles et al., 2003). Moderate accuracy in model simulation of phosphorous and nitrogen processes was also highlighted by model applications in two small watersheds located in the Missis‐ sippi Delta (Yuan et al., 2005) and in the Sydney region (Baginska et al., 2003). The capa‐ bility of the model (coupled to the BATHTUB eutrophication reservoirs model) in simulating nutrients load variations in response to land use changes in a Kansas large res‐

In applications to a small Mississippi watershed reported by Yuan et al. (2001, 2005), An‐ nAGNPS adequately predicted long-term monthly and annual runoff and sediment yield and predicted and observed runoff from individual events were reasonably close, achieving

0.91 respectively). In a small Australian watershed, mainly covered by farming and residen‐ tial land uses, acceptable model predictions (E = 0.82) were assessed for runoff at event scale

More recently AnnAGNPS was implemented at a small Nepalese watershed, mainly for‐ ested and cultivated, where the need of calibration for satisfactory runoff predictions was shown. Despite the calibration process, peak flow and sediment yield evaluation resulted in a much lower accuracy (Shrestha et al., 2006). The prediction performance of An‐ nAGNPS in a 48-km2 watershed located in Kauai Island (Hawaii, USA) was considered good for monthly runoff predictions and poor on a daily basis (Poliakov et al., 2007). Cal‐ ibration/validation tests in two small watersheds in S. Lucia Island (British West Indies) (agricultural and forested respectively) suggested that AnnAGNPS could be used under the conditions tested tested (Sarangi et al., 2007). In an agricultural river basin (374 km2

of Czech Republic suspended load following short duration intensive rainfall events was accurately predicted by the AnnAGNPS model; there the model was not suitable for con‐ tinuous simulation in large river basins with a high proportion of subsurface runoff (Kli‐ ment et al., 2008). In a 63-km2 watershed in Malaysia (tropical region which sometimes experiences heavy rainfall runoff) was well predicted while results with respect to sedi‐

Some applications in Spanish catchments covered by olive orchards showed the sensitivity of AnnAGNPS to different temporal scales in modeling runoff and sediment yield under different management systems (Aguilar and Polo, 2005) and the model applicability to pre‐ dict runoff and sediment at event and monthly scales after calibration (Taguas et al., 2009).

in Ontario (Canada) highlighted that adjustments of the monthly curve number values and of the RUSLE parameters are relevant to improve the hydrology and sediment components of AnnAGNPS, especially during winter and early spring periods (Das et al., 2009). A good model performance was obtained in terms of runoff and erosion prediction after calibration/

A calibration/validation exercise using a 10-year hydrological database in 53-km2

after the calibration of hydrological parameters Baginska et al. (2003).

and efficiency E (Nash and Sutcliffe, 1970) equal to 0.94 and

ervoir was pointed out by Wang et al. (2005).

ment load were moderate (Shamshad et al., 2008).

coefficients of determination r2

4 Research on Soil Erosion Soil Erosion

)

)

watershed

In order to consolidate use of the AnnAGNPS model in different climatic and geomorpho‐ logic conditions, this investigation has verified model prediction capability of surface runoff, peak flow and sediment yield in two small European watersheds under climate conditions typical of the semi-arid (Cannata watershed, southern Italy) and humid-temperate (Gans‐ poel watershed, central Belgium) environments respectively. Through this work we have in‐ vestigated to what extent AnnAGNPS may be expected to provide usable results in environmental conditions outside of research watersheds, where sometimes the necessary data for model calibration and validation are not available.
