水保所知识产出(1956---)知识库

黄土高原是我国土壤侵蚀最为严重的地区，每一个小流域都是独立的侵蚀产沙单元，因此研究小流域侵蚀产沙规律及泥沙来源对建立流域尺度侵蚀预报模型及优化配置小流域治理措施具有十分重要的意义。
本研究以陕西省绥德县王茂沟流域的一个淤积年限为34年(1958-1991)，淤积深度为11.325 m的闷葫芦坝为研究对象，通过采集坝控流域内沟壁、沟坡和坡耕地上的土壤样品和淤地坝全剖面泥沙旋廻样品，利用137Cs的时标功能，结合收集到的研究区相应时期的降雨资料，建立了淤地坝沉积旋廻时间坐标序列；运用复合指纹识别技术，探讨了黄土高原小流域泥沙来源演变规律以及侵蚀产沙量与降雨的响应关系，得到了以下主要结果：
（1）该淤地坝自1957-1958建成到1991年淤平，经过34年的时间共拦蓄泥沙68878 t，年均侵蚀模数为11248 t km-2 a-1。根据全球137Cs沉降特征以及强降雨侵蚀力对大沙的原则，结合该流域日降雨过程资料建立了该淤地坝沉积旋廻时间坐标序列。
（2）根据淤地坝各沉积旋廻泥沙量累积泥沙沉积量曲线将淤地坝运行史大体划分为三个阶段：1958-1964年的侵蚀剧烈阶段,其侵蚀模数为18732 t km-2 a-1；1965-1983年的侵蚀平缓阶段,其侵蚀模数为5899 t km-2 a-1；1984-1991年的侵蚀再次剧烈阶段,其侵蚀模数为19127 t km-2 a-1。分析发现，前面两个阶段的变化是因为降雨侵蚀力的变化造成的，而后一个阶段侵蚀量再次增大，与1983年农村土地家庭联产承包责任制有关，是人为活动加剧造成的。
（3）通过对淤地坝坝控流域内沟壁、沟坡和坡耕地土壤样品中15种物质的分析，利用多元判别分析，筛选出SOM、TP、Mg、χfd组成最佳指纹因子组合，并利用该组合，采用最优化混合模型计算了每层泥沙沉积旋廻泥沙来源的贡献比，结果表明每次产沙事件，来自沟壁（沟道或者深层土壤）、沟坡（表层土壤）和坡耕地（表层土壤）的泥沙贡献比变化很大，三者的变化范围分别为23.85～95.00%，0～69.97%和5.00～65.31%；在整个淤地坝淤积阶段，总共有47195 t、3478 t、18218 t的泥沙来自沟壁（沟道或者深层土壤）、沟坡（表层土壤）和坡耕地（表层土壤），分别占总产沙量的68.52%、5.03%和26.45%，证明沟道的演化过程是小流域侵蚀产沙的主要过程。
（4）通过拟合淤地坝运行期间整体侵蚀产沙量与降雨量、降雨动能、降雨侵蚀力、累积降雨侵蚀力的关系，经对比发现侵蚀产沙量（Y）与累积降雨侵蚀力（X）的关系最好，其拟合关系曲线R2为0.7559。同时按阶段分析了侵蚀产沙与降雨量、降雨动能、降雨侵蚀力、累积降雨侵蚀力的关系，也表明侵蚀产沙量与累积降雨侵蚀力的关系最好，说明累积降雨侵蚀力可以作为预报黄土高原小流域侵蚀产沙的关键因子。
关键词：黄土高原；淤地坝；沉积旋廻；泥沙来源；侵蚀产沙

Soil erosion is the important process of the surface material moving, and also is the world environment problem. Intense loss of soil and water would lead lots of problems such as Land degradation, land fertility reduces, agricultural products quality descend, water pollution and so on., and treat the human living environment. In the Loess plateau, the soil erosion is the most serious in china, and each small watershed is an independent unit of soil erosion. It would be great meaning to study the evolution rule of sediment source for establishing erosion forecasting model in basin scale and optimal allocation of comprehensive control measures in small watershed.
A check dam with 34 years deposition (1958-1991) and 11.325 m deposition depth was collected in Wangmaogou watershed in Suide County in Shaanxi Province. The soil samples were collected on the check dam profile and the surface of the slopes including three land use stytes of gully wall, gully slope and cultivated land. The concentration values of 15 fingerprint properties of each soil sample were analyzed using Kruskal-Wallis H-test and multivariate discriminant function analysis, the result showed that the tracer properties of soil χfd, SOM, P, Na and Zn could provide the best composite fingerprint for discriminating source materials on the basis of source type, and combined the time coordinates of the each sediment couplet to research the soil sediment source in the small watershed of the Loess plateau and the relation between sediment yield and rainfall. The main conclusions take follow:
(1) Sediment yield of each couplet that was lead by erosion rainfall in 1958-1991 could be counted by the Reservoir-capacity-curve, the bulk density curve and each depth of the Dam. The result showed that the check dam totally retained 68878 t from 1958 to 1991. Through studying the 137Cs content of each couplet of the check dam, we analyzed the 137Cs distribution characteristics in the check dam, combined the sediment yield and the daily precipitation of 1958-1991 from the local station, and  with the principle of strong rainfall erosion power leading more sediment yield, the time coordinates of the each sediment couplet was established.
(2)According to the accumulative sediment yield curve of each sediment couplet yield, the working time of the check dam could be divided into three stages. The result showed that the soil erosion was strong in the initial stage of the dam construction from 1958 to 1964 with the soil erosion modulus of 18732 t/km2.a, then the soil erosion changed smoothly from 1965 to 1983, with the soil erosion modulus of 5899 t/km2.a, but strong again from 1984 to 1991 with the soil erosion modulus of 19127 t/km2.a. From analyzing we found that the rainfall erosion power lead the change of the first two stages, and the third stage was relation to the land police of our country, and was lead by intensify human activity.
(3) According to analysis 15 kinds fingerprint factor in the soil sample of three sources of gully wall, gully slope and cultivated land in the small watershed, χfd, SOM, TP and Mg formed the best fingerprint identification compositions, and calculated the sediment contribution that 23.85～95.00% was from the gully wall, 0～69.97% from the gully slope and 5.00～65.31% from the inter-gully land. And in the hole working time of the check dam, the sediment yield were 47195 t, 3478 t and 18218 t from the gully wall, gully slope, inter-gully land, and the contribute rate were 68.52%, 5.03% and 26.45%. The evolution process of the gully was the main erosion process of the small watershed.
(4)According to researching the relation of the sediment yield(Y) with the precipitation, rainfall kinetic energy, rainfall erosivity(X), accumulative rainfall erosivity, we found that the relation between sediment and accumulative rainfall erosion power was the best, and the R2 was 0.7559. At the same time we researched the relation between the sediment yield and the precipitation, rainfall kinetic energy, rainfall erosivity, accumulative rainfall erosivity of the three stages, we also found that the relation between sediment yield and accumulative rainfall erosion power was the best. The result says that the accumulative rainfall erosion power can be used to forecast the soil erosion of a small watershed in Loess Plateau.
Key words: Loess Plateau; Check Dam; sediment couplet; sediment source;
sediment erosion