Identification of sediment sources in a small rural drainage basin

In this study, the fingerprinting method, which uses geochemical variables to distinguish sediment sources and classify suspended sediments through multi-variate statistical analysis, was applied to a small rural drainage basin in southern Brazil. The drainage basin represents a typical agricultural ecosystem, in which peasants cultivate tobacco in fragile areas (headwaters), liable to severe erosion. By classifying suspended sediments, it was possible to identify the relative contribution from different sources and thus to suggest actions that would limit soil loss. Results showed that the predominant contribution was from fields and roads, contributing 64% and 36%, respectively, of the sediments sampled in the drainage basin control section, with the relative proportion of contribution from each source varying over time and according to management and soil cover in the fields and maintenance-work performed on the roads.