| چکیده انگلیسی مقاله |
It is critical to determine soil erosion rates and sediment yields under the condition of ecological restoration on the Loess Plateau, and the sediments retained by check–dams document the soil erosion history in a small watershed. We selected a check–dam system to reconstruct the long–term sediment yield in the Fangta catchment on the middle of the Loess Plateau. Storage capacity curve method was applied to estimate the total sediment deposition of check–dam systems, a total of 725.82 thousand tons sediment was trapped by the check–dams in the Fangta catchment from 1975 to 2013. Two abrupt–change points of 1987 and 2003 were detected by the double mass curve method, the average catchment sediment yields were 5273.63 t/(km2·a) in Stage-1 (1975–1987), 1734.09 t/(km2 ·a) in Stage-2 (1988– 2003) and 2653.10 t/(km2·a) in Stage-3 (2004–2013), represented intense erosion, mild erosion and moderate erosion, respectively. Since in Stage-2, the sediment yield variation in the Fangta dam–controlled catchment was mainly affected by human activities and its contribution reached 97%. When the average annual erosive rainfall reached about 300 mm, 350mm and 400 mm in the Fangta catchment of the loess hilly–gully region, the soil erosion intensity changed gradually from mild erosion to moderate erosion and then to intense erosion. 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 transported to the downstream river network gradually. Therefore, check–dam systems were important carriers to reconstruct the historical sediment yield in small and ungauged watersheds. The results of this study not only serve as a basis for obtaining the reliable information on erosion and sediment yield in the small dam–controlled catchments, but also provide a useful reference for implementing sustainable ecological restoration in the future on the Loess Plateau. |
