Sediment Yield at Catchment Scale Using the SWAT (Soil and Water Assessment Tool) Model

Abstract

Suspended sediment and sediment-bound pollutants deteriorate the ecological status of many freshwater bodies around the world. Maintaining and restoring the ecological status require planning strategies that strongly rely on integrated basin models that correctly identify the main sources of sediment within the catchment and quantify the sediment yield. This study assesses the applicability of the SWAT (Soil and Water Assessment Tool) model to simulate sediment yield in a small (16-km2) rural catchment (Corbeira) in northwest Spain and determines the contribution of different land uses to sediment export at the catchment outlet. The SWAT model was calibrated and validated for monthly sediment yield using measured sediment yield data obtained at the catchment outlet from 2005 to 2010. The results showed good agreement between measured and simulated monthly sediment values (R2 values of 0.67 and 0.84, percent bias values of 6% and 12%, and Nash-Sutcliffe efficiency values of 0.48 and 0.50 during the calibration and validation periods, respectively), indicating that SWAT is a useful tool for simulating sediment yield under the conditions prevailing in the Corbeira catchment. Therefore, the validated model can be used to evaluate the influence of alternate soil management practices in controlling erosion and sediment yield in this catchment. Cultivated lands (4% of total catchment area) were the largest contributors (79%) of sediment yield in the study area, where the soil formation rate for conditions prevailing in Europe was slightly exceeded.