Using reservoir deposits to quantify the source contributions to the sediment yield in the Black Soil Region, Northeast China, based on the fingerprinting technique

Abstract

Identifying patterns of sediment dynamics is an important aspect of understanding soil erosion processes and developing reasonable management strategies to address environmental problems and assess the ecological functions of soil and water conservation measures. In this study, the sediment fingerprinting technique was applied in order to quantify the relative contributions of sediment to the Hebei catchment in the black soil region of Northeast China, with the aim of determining the response of soil erosion to recent changes in land management. Within an area of approximately 28 km2, three potential sediment sources were identified based on land use types. They included cultivated topsoil, uncultivated topsoil, and gullies. A total of 69 sediment source samples were collected from potential sediment sources from 27 sampling sites for cultivated topsoil, 18 sampling sites for uncultivated topsoil, and 24 sampling sites for gullies. Six uniformly spatially distributed sediment cores were sampled from the Liudui reservoir. The Walling–Collins model was optimized using a genetic algorithm combined with the Latin hypercube sampling procedure. The results indicated that cultivated topsoil and gullies were the primary sediment provenances and that gully erosion is as important as rill and interrill erosion. According to the mean sediment contributions of the six deposited sediment cores, the sediment contribution from cultivated topsoil was 50.6%, ranging from 34.4% to 63.7%, whereas gullies contributed 42.9%, ranging from 30.1% to 57.8%. However, the sediment from uncultivated topsoil (mainly containing forest and grassland) contributed only 6.5%, with a range of 5.0% to 7.8% over the last few decades with a mean absolute fit of 0.95. This indicated that caution is needed in when using only a single core to provide results for a reservoir. Over the 1976–2016 period, rill and interrill erosion showed a general decreasing trend, whereas gully erosion showed an increasing trend. According to the sedimentation depth and time marks based on the 137Cs and D50 peak horizon and decayed vegetation layer in the six sediment cores, sedimentation rates during 1976–1998 and 1999–2016 were 1.6 cm yr−1 (14.4 kg m−2 yr−1) and 0.9 cm yr−1 (7.6 kg m−2 yr−1), respectively. For the entire time series (1976–2016), the sedimentation rate was 1.2 cm yr−1 (10.7 kg m−2 yr−1). A good correlation exists between the distance from the reservoir entrance and sediment contribution/mean annual sedimentation rate (r2 > 0.68, except uncultivated topsoil).