溶质示踪法研究典型水蚀区坡耕地侵蚀过程及其剥蚀输沙互馈机制

Quantitative analysis of soil erosion rates and sediment transport capacity plays an important role to establish a basic understanding of soil erosion process and build physical process models. Accurate measurement of temporal-spatial variation process of sediment concentration and flow rate is the key to the study on detachment-transport relationship of soil erosion. It is difficult to measure the flow velocity and sediment concentration on the sloped cropland due to the shallow depth of the erosive runoff. .In this project, solute tracer method is learned to measured both flow velocity and sediment concentration and then used to study the erosion process of sloped cropland: (1) to improve the Pulse Boundary Method for measuring the shallow water flow for soil erosion base on the analysis of the characteristics of acceleration after the solute was injected in to the flow; (2) to propose a new method to determine sediment concentration of erosive shallow flow with solute tracer base on the quantitative analysis of coupling between the diffusion coefficient and sediment concentration; (3) to develop a systematic experimental method and related algorithm with solute tracer to determine the soil detachment and transport capacity for soil erosion on sloped cropland, and to establish the feedback relationship between the detachment and transport capacity during the sloped cropland erosion.

定量分析土壤剥蚀率、输沙能力对认识土壤侵蚀过程及构建物理过程模型具有重要作用，含沙量和流速时空变化过程是剥蚀输沙互馈机制研究的关键。因此，精确实时测量土壤坡面薄层水流流速及含沙量时空变化数据具有重要意义。针对坡耕地土壤侵蚀径流流速及含沙量时空变化过程定量监测困难的问题，拟采用溶质示踪测量含沙水流冲刷试验中径流电导率变化过程，甄别不同水力条件下溶液滴入径流后随径流运动所需加速过程的特征，改进脉冲边界模型测算方法；定量分析水动力弥散系数和含沙量的耦合关系，得到溶质示踪测量薄层水流泥沙含量的方法；以典型水蚀区坡耕地侵蚀为研究对象，提出获取坡耕地侵蚀产沙输沙过程的时空动态数据的溶质示踪方法及装置，分析典型水蚀区坡耕地径流侵蚀输沙对不同水动力条件的响应规律，揭示不同水沙耦合作用下坡耕地侵蚀过程中剥蚀输沙互馈机制。解决土壤侵蚀模拟与预报模型的关键技术问题，为土壤侵蚀预报物理模型参数获取提供新的途径。

含沙量和流速时空变化过程是剥蚀输沙互馈机制研究的关键。本研究通过溶质示踪测量含沙水流冲刷试验，定量分析了径流含沙量与扩散系数的关系，获得了不同条件下含沙量与溶质扩散系数的耦合关系式；研究了不同水力条件下溶液滴入径流后随径流运动所需加速过程特征，验证了惯性作用对电解质脉冲边界模型测量流速的影响，该影响随距离的增加而减小；同时改进了脉冲边界模型测算方法，提高了测量精度及测量效率；通过室内坡耕地冲刷模拟实验，研究了坡耕地径流流速、含沙量时空变化特征，并分析了不同水动力条件下剥蚀速率与输沙能力间的响应规律，揭示坡耕地水流剥蚀与泥沙输移的互馈关系。项目共计发表论文3篇，其中SCI收录2篇。正在投稿文章2篇，申请待授权发明专利1项。本研究为解决土壤侵蚀模拟与预报模型的关键技术问题，为土壤侵蚀预报物理模型参数获取提供新的途径。