Abstract
It is critical to determine soil erosion rates and sediment yields under ecological restoration conditions on the Loess Plateau. Sediments retained in check-dams document the soil erosion history in a small watershed. We selected the check-dam systems to reconstruct the long-term sediment yield in a restored agricultural catchment on the Loess Plateau. The storage capacity curve method was applied to estimate the total sediment deposition of check-dam systems, and 725.82 thousand tons of sediment was trapped in the check-dams systems from 1975 to 2013. Two abrupt change points were detected in 1987 and 2003 using the double mass curve method; the average catchment sediment yields were 5,273.63 t/(km2·a) in Stage-1 (1975–1987), 1,734.09 t/(km2·a) in Stage-2 (1988–2003), and 2,653.10 t/(km2·a) in Stage-3 (2004–2013), represented intense erosion, mild erosion, and moderate erosion, respectively. In Stage-2, the sediment yield variation in the Fangta catchment was mainly affected by human activities, and its contribution reached 97%. According to the hierarchical cluster analysis, the soil erosion intensity changed gradually from mild to moderate and then to intense when the average annual erosive rainfall reached approximately 300, 350, and 400 mm in the Fangta catchment of the loess hilly-gully region. Approximately 6.1–42.6 % of the sediment was deposited along the way since 2003 when the sediments generated by erosion in small watersheds were gradually transported to the downstream river network. Therefore, check-dam systems are important carriers for reconstructing the historical sediment yield in small and ungauged watersheds. The results of this study not only serve as a basis for obtaining reliable information on erosion and sediment yield in small dam-controlled catchments, but also provide a useful reference for implementing sustainable ecological restoration in the future.
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