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Spatial and Temporal Evaluation of Soil Erosion with RUSLE: A case Study in an Olive Orchard Microcathment in Spain
Citation:
Taguas, E. V., P. Cuadrado, J. L. Ayuso, Y. YUAN, AND R. Perez. Spatial and Temporal Evaluation of Soil Erosion with RUSLE: A case Study in an Olive Orchard Microcathment in Spain. Journal of Geophysical Research: Earth Surface. American Geophysical Union, Washington, DC, 35(7):750-760, (2010).
Impact/Purpose:
Soil erosion is a serious problem in Spain where 46% of the national territory shows larger rates of soil losses than tolerance values (MMA, 2007). In fact, higher erosion rates than 50 t.ha-1 year are expected in mountainous agricultural regions associated to orchard crops such as Andalusia (MMA, 2007). In this region, there are 1.48 Mha of olive orchards (CAP, 2007) that constitute a key crop in terms of income, employment and environmental impact.
Description:
Soil loss is commonly estimated using the Revised Universal Soil Loss Equation (RUSLE). Since RUSLE is an empirically based soil loss model derived from surveys on plots, the high spatial and temporal variability of erosion in Mediterranean environments and scale effects provoke that studies evaluating the model on other spatial units such as the microcatchment are necessary. In this study, different topographic and soil surveys were carried out on a microcatchment of 6.7 ha in a mountainous area under no-tillage farming with bare soil to examine spatial and temporal results produced by RUSLE. The height difference of microrelief through GPS measurements was set on a control area in the microcatchment to compare observed erosion and deposition with RUSLE predictions. It was found that erosion points located on zones highly correlates with RUSLE predictions while the distribution of deposition points showed no correlations with RUSLE predictions. Secondly, time series of daily rainfall data were used to calculate annual erosivity and efforts were made to fit rainfall data to an appropriate distribution function. It was found that rainfall distribution fit the Pearson type III distribution function the best. Then, efforts were make to quantify the long term erosion and to check the suitability of land-use and management under different thresholds of tolerance. It was found values of erosivity with a return period of 10 years in the study area generated a mean annual erosion of 5 t.ha-1.year--1. On the study scale, RUSLE allowed to locate the most erosive areas and to combine the suitability of the soil land-use and the management with the frequency of the annual erosivity. In addition, an annual sediment delivery ratio of approximately 47 % was estimated for the period of 2005-06.