Sediment Source And Sediment Yield Intensity In Check Dam Controlled Watershed Of Loess Plateau

Huangfuchuan is one of the main tributaries with abundant sediment and coarse sediment,and also the birthplace of coarse sediment on the downstream of the Yellow River. Check dam isan important soil and water conservation measures to channel in Loess Plateau. Not onlyeffectively intercept water and sediment, but also the sediment which reserve in the check damcarry a wealth of environmental information. The sediment source and sediment yield in thecheck dam can be accurately identified by the alluvium information. It is a new mean for the lackof hydrological and sediment data to research soil erosion quantitatively.In this paper, a typical small catchment in Huangfuchuan River was selected as the studyobject. With the theory of fractal, principal component analysis and factor analyzed were studiedand the relationship between the check dam profile and the potential sediment source had beenobtained. The time scale of the sediment process had been set up by the characteristics alluviuminformation,the time scale of137Cs and runoff-sediment data.The corresponding deposition layer with rainfall can analyzed sediment yield intensity incheck dam. A combination of fingerprint technology and statistical modeling have been used tocalculate the contribution rate of sediment and to determine the primary source.The following main results:（1）The characteristics of the alluvium information of check dam were analyzed. Theresults show that the well difference between the check dam profile and the potential sedimentsource in particle size. The137Cs content had an relationship with the fine sediment and thedistribution of magnetic susceptibility and particle size. The correct of the couplet of depositionbe illustrated and the primary source had been determined.（2）Obtained the relationship between the check dam profile and the potential sedimentsource. There were good linear relation from the soil texture and particle size. The fractaldimension D value on the vertical section within the check dam decreased with the increase ofparticles size. The fractal dimension D value of grassland is uniform, bare land is the secondary,and the most narrow distribution is sandstone. In the check dam profile the seven principalcomponents had been filtered, and the five principal components in the potential sediment source.Both the first and second principal component is the most significant and the more clusteringindex. The results of fingerprint identification technology become an important value. （3）According to the accumulative sediment yield of each sediment couplet and the rainfallevents in check dam, the intensity of erosion and sediment yield of a small watershed wasanalyzed. Results show that the spetical check dam was built in1958by the artificial ramming,and washed out in1973. There is exactly16years of the working time for the check dam. Thehigh of the check dam is9.9m. The storage capacity of check dam is8.5472×104m3, the damfield has been formed1.7841×104m2and accumulated sediment deposition is12.6627×104t.There was a strong soil erosion with the soil erosion modulus of13190t/(km2·a). During therunning of check dam in each of the erosion and sediment yield, it was presented fluctuationtrend. The strongest sediment yield was in1959with sediment deposition of2.005×104t,eliminated in1973when the check dam has been washed out. And some years of sediment werealmost zero. From1963to1972, each of the sediment yield can be increased by fluctuation.（4）According to fingerprinting analysis method in the three source samples with bare land,grassland and sandstone, the sediment source of small watershed is determined. All indexeswhich we have been measured in the laboratory were analyzed, and the optimum combinationfactor was Nb, Sb, U, and fd(%). The results indicated that the three sources had fairlydifferences in the sediment contribution. The contribution of the sandstone is the maincontribution rate by61.7%for the check dam, bare land which accounted for32.3%, was thesecondary. The minimum contribution rate by only6.0%and showing largely discrepancy fromyear by year was meadow. Using test of goodness of fit is0.87, in addition to comparison theresearch achievements of predecessors in neighboring region, the results showed that themultiple mixed model satisfied the requirement for the consequence.