黄土高原极强烈侵蚀区水沙变化的空间尺度效应及其区域差异

Sediment dynamic responding to the environment change has received much attention for the Yellow River. Most of the current studies addressed the macro-scale watershed, which is generally larger than the river basin of the first-order tributary of the Yellow River. However, many studies have revealed that the large-sized watershed generally remains insensitive to the environmental change or the human impact. Moreover, the sediment dynamic may have considerable region differences in the Loess Plateau. Bearing this in mind, this project was designed to select four most serious erosion centre of the Loess Plateau as study areas, intending to study their sediment dynamics in the context of the spatial scale and the regional difference, not only addressing the change of the river sediment yield as many previous studies have done, but also addressing the change of other factors important for the fluvial processes such as the flow-sediment relationship, the sediment concentration, the sediment particle size and the yield of the coarse sediment. First, we intend to examine the changing trend of the runoff and the sediment yields at multiple spatial scales; Then, we shall analyze the driving forces for sediment dynamics and calculated their relative contributions at different spatial scales, aiming to determining the change of sediment reduction and the major driving force responding to spatial scales; Finally, we shall detect the difference of sediment dynamic between the Coarse Sandy Hilly Catchments region and the Fine Clayey Hilly region of the Loess Plateau, and between the hilly loess areas and the plain loess areas, aiming to determine the sediment dynamic responding to the different loess landforms and the different types of hyperconcentrated flows, the latter of which make the fluvial processes of the Loess Plateau distinct form other regions around the world to a considerable degree. The object of the project is to shed more light on the understanding of the sediment dynamic of the Loess Plateau during the period 1950-2010 in terms of spatial scales and regional difference. In this way, we hope to provide theory support to the watershed management in changing environments in the loess Plateau.

黄河水沙变化目前引起了广泛关注。绝大部分的相关研究都集中在黄河中游一级支流及以上尺度，忽略了中小尺度的研究和不同尺度之间的联系。然而，许多研究表明，大流域水沙过程通常未必对环境变化敏感，黄土高原不同区域水沙变异规律也可能并不相同。有鉴于此，本项目以黄土高原4个极强烈侵蚀中心为研究区，从空间尺度和区域差异的角度进行水沙变异规律研究，不仅研究产沙总量的变异，也研究水沙关系/含沙量、泥沙粒径/粗泥沙产沙模数等的变异。首先分析不同尺度流域水沙过程变化趋势；然后进行多尺度驱动因素分析和贡献率计算，确定减沙效益和主导驱动因素随空间尺度的变异及其机理；最后，分析水沙变化在多沙细沙区和多沙粗沙区、黄土丘陵区和黄土高塬区的异同，确定水沙变化对不同黄土地貌类型和不同高含沙水流类型的响应。本项目以揭示仅60年来黄土高原不同空间尺度和不同区域的水沙变异规律为研究目标，为变化环境下的黄土高原治理提供相关理论基础。

气候变化和人类活动影响下的黄河中游水沙变化研究目前广受关注。本项目以黄河中游极强烈侵蚀区的河流为研究区，从空间尺度和区域差异角度展开黄河中游水沙变化研究。项目系统分析了流域产沙模数、径流含沙量、水沙关系等水沙过程重要参数随空间尺度的变异规律，定量评价了其空间变异程度，发现了流域产沙和水沙关系存在很好的空间不变特性，分析了这种空间不变特性随随流域治理而发生的时间变异，揭示了其主导驱动机制，并分别以河龙区间和泾河流域为研究区，分析了黄土高原多沙粗沙区和多沙细沙区河流水沙过程对近60年来环境变化的响应，研究成果可为变化环境下黄土高原流域治理提供理论支持。本项目执行期间，较好地完成了项目目标，共计发表论文13篇，包括8篇SCI收录论文和1篇EI收录论文。