黄土高原淤地坝对流域侵蚀过程调控机理研究

Check dam is one of the most important measures of gully control being widely used on the Loess Plateau, which has theoretical and practical significance for its great effects on the process of runoff and sediment. Scientific understanding of the regulatory mechanism of check dam on watershed erosion processes, improving the erosion-control efficiency of dam system, is a key scientific issue need be urgently solved in gully erosion in the Loess Plateau. This project intends to employ field observation and simulation experiment combining distributed hydrological simulation and spatial analysis technology. The changed runoff process and sediment particle distribution effected by the structure and layout of check dams will be studied. The regulation function of check dam system on the temporal-spatial distribution of channel runoff energy will also be analyzed. Then it is expected to clarify the transition between kinetic energy and potential energy in the runoff process. The relationship between runoff erosion energy and sediment yield will be established. The effect of check dam system on surface hydrological connectivity will be quantified. The impact of watershed runoff time change on the channel sediment transport- deposition process will be clarified. Consequently, the controlling mechanism of check dam on sediment erosion will be systematically revealed. The results will provide a theoretical basis for optimizing dam system configuration and improving the safety of dam system. It will be of important practical significance for promoting eco-building in the Loess Plateau.

淤地坝是黄土高原主要的沟道治理措施，对流域侵蚀输沙过程产生深远影响。科学认识淤地坝对流域水蚀过程的调控机理，提高坝系侵蚀调控效率，是黄土高原沟道侵蚀治理中亟需解决的关键科学问题。本研究拟通过野外观测及模拟实验，并结合水文模拟和空间分析技术，系统研究淤地坝结构和坝系布局对沟道径流的调蓄作用及泥沙颗粒分布的影响，分析淤地坝系对坡面-沟道径流汇聚过程中势能-动能转化与径流侵蚀能量的消耗，建立径流侵蚀能量与产沙量之间的关系，量化淤地坝系对地表水文连通度的改变，阐明流域径流滞时变化对沟道泥沙输移-沉积过程的影响，揭示淤地坝系对流域侵蚀产沙输移过程的调控机理，为优化流域坝系配置，提高坝系安全提供理论依据，对推动黄土高原地区生态建设具有重要的实际意义。

淤地坝是黄土高原主要的沟壑整治工程，对流域侵蚀输沙过程产生深远影响。科学认识淤地坝对流域水蚀过程的调控机理，提高坝系侵蚀调控效率，是黄土高原沟道侵蚀治理中亟需解决的关键科学问题。项目通过野外观测，结合水文模拟和空间分析技术，揭示了淤地坝系对流域侵蚀产沙输移过程的调控机理。取得的主要结论如下：（1）2012.7.15和2017.7.26暴雨，王茂沟流域泥沙输移比降至0.15和0.24，坝系建设极大的降低了流域泥沙输移比，改变了流域原有的输沙关系；（2）由于淤地坝影响，径流中携带的泥沙粗颗粒先沉积，然后是细颗粒，沉积层从上到下泥沙越来越粗，形成了以砂粒-粉粒-粘粒为主的沉降次序，且随着沟道级别的增加，淤积泥沙的粒径越来越小；（3）王茂沟流域的平均流域滞时为117min，李家寨的平均流域滞时为38min，王茂沟平均流域滞时是李家寨的3倍，淤地坝显著的推迟了流域洪峰出现时间，基于图论，分析了淤地坝对径流过程的作用机理；（4）沟道未建坝时，流域支沟的侵蚀功率大于主沟，主沟上游到下游，流域的径流侵蚀功率基本保持不变，当坝系建成后，整个流域从支沟到主沟的径流侵蚀功率均明显减小；（5）概括出淤地坝建设的影响因素为限制性因素和规模性因素，并确定了整个黄土高原骨干坝布设潜力；（6）建立了淤地坝系减沙量计算公式，并对黄河中游淤地坝系减沙贡献率进行了计算，淤地坝系拦沙能力从1965年到1975年逐步上升，从1976年到1987年，保持在1.7亿t上下，从1988年到2008年开始增加，特别是2000年后，淤地坝拦沙能力增速明显，至2008年达到最大值，为3.54亿t，2008年后，淤地坝拦沙量开始下降。研究成果为优化流域坝系配置，提高坝系防洪能力提供了理论依据，对推动黄土高原地区生态文明建设具有重要的实际意义。