Evaluating and modelling the hydrological and erosive behaviour of an olive orchard microcatchment under no-tillage with bare soil in Spain

Despite the high risk of erosion in olive Orchards located in mountainous areas in Spain, little research has been carried out to account for the complexity and interaction of the natural processes of runoff and soil erosion on the catchment scale or small catchment scale. In this Study, a microcatchment of 6.7 ha in a mountainous area under no-tillage farming with hare soil was Set Up to record runoff and sediment. Soil erosion and runoff patterns were monitored Over a two-year period. Totally events were observed. The data were analysed, and then Used to calibrate the, AnnAGNPS model, which allowed Lis to complete the data period and describe the hydrological and erosive behaviour on a monthly and annual basis. A high variability in catchment responses was observed, due to differences in the storms and to the effect of the surface Soil moisture content. Maximum intensities of 10 and 30 min determined the final runoff Values while the total sediment leads were dependent on the rainfall depth. The impact of management on the reduction of porosity can explain the relationship between runoff and intensity in the microcatchment. However, the impact of the spatial scale meant that the transport of sediment required substantial rainfall depths to ensure a Continuous flew front the hillslopes. The results of the calibration (E > 0.60 and r > 0.75) on the event and monthly scale confirmed the applicability of AnnAGNPS to predict runoff and erosion in the microcatchment. The predicted average runoff coefficient was 3.3% for the study period and the total average Sediment loads, 1.3 Mg/ha/yr. Despite these low Values, the model Simulation Showed that much larger runoff coefficients and soil losses can be expected for periods with several consecutive years in which the annual rainfall depth was over 500 mm). The use of cover is recommended to prevent the high levels of erosion associated with these conditions. Copyright (C) 2009 John Wiley & Sons, Ltd,