| The Loess Plateau is characterized of considerable large deep gullies,and is famous for serious soil erosion.It is the main sediment source of the Yellow River.To better control the severe soil loss,a series of soil and water conservation measures have been undertaken since1950s,such as terraces,check-dams,returning farmland to forest?grassland?.Significant decrease in soil erosion and sediment yield has been detected on the Loess Plateau due to the measurement implementation.As well,sediment load discharged into Yellow River showed sharp decrease during the past decades.Sediment stored by check-dams records the historical process of erosion and sediment yield in small watersheds,which provides an outlet for soil erosion research in areas with missing data.This study collecteds relevant literature by searching"Huangtugaoyuan","Loess Plateau","Yudiba"and"Check dam"on the inversion of erosion and sediment yield by Check-dam.The aim of this study was to clarify temporal changes of sediment yield in different sub-areas of Loess Plateau before and after the implementation of returning farmland to forest?grassland?“GFGP”and in different periods.This study selected four typical check dams in Dali River and Huangfuchuan watershed through remote sensing interpretation and field investigation to investigate sediment yield changes.Field sampling were undertaken samples were sampled and brought back for analysis.According to the sediment deposition characteristics,the cyclone levels were divided according to the principle of heavy sediment corresponding to heavy water.The sediment yield time series of warping dam erosion was established,the erosion and sediment yield process of the basin was inversed,and the variation characteristics of erosion and sediment yield intensity in different periods were clarified.The potential provenance types are divided according to the erosion and sediment yield process in the dam,at the same time,the optimal combination of fingerprint factors with diagnostic ability is selected by statistical method according to soil characteristics,and the sediment contribution of potential source is solved by Tongduo multivariate mixed model.identify the main sediment yield parts of the dam-controlled watershed,so as to achieve"measures according to source conditions"and optimize the allocation of soil and water conservation measures.The conclusions of this paper are as follows:?1?The implementation of returning farmland to forest?grassland?has significantly reduced sediment yield.The meta-analysis showed that sediment yield decreased 48.4%,80.2%,60.6%and 43%,respectively,when comparing to those before GFGP in the hilly and gully sub-regions of the Loess Plateau.?2?The average sediment yield of 8288t·km-2·a-1 and 5230t·km-2·a-1 were lower than17315t·km-2·a-1 and 13459t·km-2·a-1 in Huangfuchuan typical watershed by comparing the erosion and sediment yield of typical small watersheds before and after GFGP in Dali River and Huangfuchuan.?3?The sediment sources of Dujiahe and Hujitu typical warping dams were studied,and the two dam-controlled small watersheds were divided into three provenance types.among them,the sediment contribution relationship of Dujiahe dam is steep slope gully wall?54%?>cultivated land?26%?>slope grassland?20%?.The sediment contribution relationship of Hujitu dam is steep slope gully wall?47%?>slope grassland?31%?>woodland?22%?. |
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