Using two contrasting methods with the same tracers to trace the main sediment source in a mountainous catchment

Abstract

Assessing the contribution of sediments from different sources is essential to understand erosive processes and formulate further soil conservation strategies to address environmental problems. In this study, we combined the source fingerprinting approach with geochemistry, including comparison of potential sources, and distribution pattern of major elements, to estimate the different land-use relative contributions to streambed sediment in the Luowugou catchment (13.5 km2) located on the Heishui River, the first branch of the Jinsha River, China. A total of 57 samples from stream bank, cropland, grassland, forest land, and sediments were collected, and then, 15 elements were analyzed for each sample. The fingerprinting results demonstrated that the stream bank (62.4%) had the greatest relative contribution to the bed sediment yield, while cropland, grassland, and forest land contributed 18.6%, 14.9%, and 4.1% to the bed sediments, respectively. In comparison to the fingerprinting method, even though the results upon geochemistry only provide a qualitative assessment, the ranking of sediment contributions based on geochemistry was consistent with the sediment fingerprinting ranking, that is, stream bank>cropland>grassland>forest land. Our findings suggest that the focal point for sediment control practices should be the stream bank rather than cropland in the region. Geochemistry can result in an important means in validating the fingerprinting results.