Evaluación del modelo WEPP para predecir la erosión hídrica en pastizales semiáridos del noreste de la Patagonia

mathematical models are useful tools to predict soil loss by water erosion. the recent development of the wepp model and its use in assessing the risks of erosion in rangelands has led to significant advances in the field of erosion and soil conservation of these ecosystems. in this work we examine the efficiency of the wepp model in predicting the hydrological processes and soil erosion in semiarid rangelands of the northeast chubut province. three plant communities along a soil degradation gradient were identified: grass with scattered shrubs (eh), grass-shrubs (eha), and degraded shrub steppes (ea). in each of these communities simulated rainfall (100 mm h-1 for 30 min) was applied on 1 m2 (0.6 x 1.67 m) plots and total runoff and sediment production were collected. using the soil surface condition data from each plot, runoff and sediment production were estimated by means of the wepp model. we found a low efficiency of the wepp model to predict runoff (efficiency, e = 0.14) and soil erosion (e = -0.93). the wepp-estimated runoff and soil losses showed high sensitivity to changes in rainfall and slope parameters and moderate sensitivity to changes in soil cover, texture, soil erodability and effective hydraulic conductivity. the runoff and sediment production estimated by the wepp model were significantly different among plant communities (p < 0.05). the difference between the estimated and observed mean values varied in the different plant communities: runoff according to the wepp model was 55.5% greater in the eh and sediment production was 69.6, 62.7 and 17.5% lower, respectively, in the eh, eha, and ea than the observed values. these results suggest that it is necessary to calibrate the model for local conditions and to incorporate rangeland stratification according to the different soil-vegetation units.