Sediment sources and their impacts on a check dam-controlled watershed, Loess Plateau, China

Soil erosion is a major issue in Loess Plateau, China, and quantitative analyses of sediment sources are crucial for soil erosion control. In this study, a combination of flood couplet analysis and composite fingerprint identification was used for historical reconstructions of soil erosion in sediment source areas in Loess Plateau. Each flood couplet was constructed based on sediment Cs-137 activity, and past soil erosion was calculated using soil bulk density and storage capacity curves. The contribution rates of the sediment sources were calculated using the fingerprinting method, and the amount of erosion in the sediment source areas was estimated. The best fingerprint combination (Cr, Ni, V, and TOC) enabled a 97.2% recognition of sediment sources from 29 flood events (1956-1990) in the Loess Plateau. The contribution rates of gullies, farmland, grassland, and shrubland were 44.89%, 26.38%, 10.49%, and 18.24%, respectively. These four land use types contributed 1,227, 751, 512, and 279 tons of sediments, respectively. Re-vegetation decreased soil erosion (1966-1983), whereas deforestation increased soil erosion (1956-1965 and 1984-1990). Rational soil and water conservation measures on slopes and check dam construction in gullies are therefore suggested to mitigate erosion.