坡耕地微地形水力连通性及入渗机理研究

Micro-topography of slope farmland affect the development of soil crust and depression water during the rainfall, and the evolution of soil crust and depression water determine the development of runoff of slope farmland, because soil crust block water infiltration, but depression water promote rainfall infiltration. In this study, we will conduct artificial rainfall experiment to obtain these intents: Firstly, measuring systematic and describes quantitatively the infiltration effects of soil curst and depression water. Secondly, determining characteristics of soil crust and depression water in different micro-topography to describe the hydrological connectively with the apace change of soil curst and depression water distribution. Thirdly, analyzing the dynamic change of soil crust and depression water to form a connection function containing the transformation by utilizing the micro-topography DEM, which can be gotten by close-range photography. Fourthly, building the model of depression filled with runoff to describe accurately the runoff law of micro-topography and explore to establish the distributed infiltration prediction model based on relationship between the micro-topography and erosion, which reflects the mechanism of slope runoff. All this results will supplement new content for the study on quantitative production of slope runoff and provide scientific guidance for slope management and efficient use of water and soil resources to promote discipline innovation.

坡耕地微地形影响着降雨过程中土壤结皮及洼地积水的发育，结皮阻滞水分入渗，而洼地积水促进降雨入渗，结皮和积水演化决定着坡面产流的发育。本研究通过人工降雨，系统测定并定量描述结皮的阻渗及积水的促渗作用；测定不同微地形单元的结皮特征和积水特征，描述地表水文连通性随结皮和积水分布的空间变化；根据坡面侵蚀演化，采用近景摄影生成的微地形DEM，分析结皮和积水的动态变化，形成包含变化过程的连接函数，构建结皮阻渗基础上的 “洼地蓄满产流”模式，基于分布式流域水文模型的降尺度应用，精确描述坡面微地形产流规律，探索建立反映微地形水蚀形态转化关系的分布式入渗预报模型，旨在阐明微地形演化条件下，坡面产流的内在过程与相互作用机理。研究结果将为坡面产流定量化研究增添新的内容，并为坡面耕作管理及水土资源高效利用提供科学指导，推动学科创新与发展。

提高土壤侵蚀预测精度是国际土壤侵蚀定量化研究迫切需要解决的重要科学问题，坡耕地降雨侵蚀研究能够为黄土区土壤侵蚀的产流定量化提供科学指导。.本项目针对坡耕地微地形对降雨过程中土壤结皮的发育，通过室内外人工降雨实验模拟黄土坡耕地微地形对降雨侵蚀的影响。运用高精度激光扫描、地统计学、计算机模拟等技术和理论，研究了微地形条件下黄土耕作坡面的结皮发育，进而开展结皮发育下不同类型结皮的物理学特征研究，阐明了结皮对降水入渗、结皮裂隙发育之间的相互作用机理，探讨黄土坡耕地结皮的阻渗效应。研究结果表明：（1）不管是结构结皮还是沉积结皮，0～5min的降雨历时内结皮厚度和密度都随着时间逐渐变大；45～60min的降雨历时内结皮厚度和密度都随着时间趋于稳定。（2）结构结皮和过渡带结皮的土壤可蚀性K值呈现降低趋势，土壤的抗蚀能力可用土壤崩解性解释。（3）微地形不同空间位置下，垂直剖面中不同沉积层粒径含量有所差异，但其构成均以粉粒为主且所占比例超过50%。降雨历时与土壤颗粒组成息息相关，随降雨历时的延长，土壤所含砂粒逐渐减少，而黏粒逐渐增加，粉粒变化程度不大。（4）土壤结皮影响土壤裂缝的产生与发育，沉积结皮裂缝的交点数和端点数的平均值要高于结构结皮。（5）坡面结皮很大程度上影响坡面土壤水分入渗，限制土壤水分与环境的交换。土壤结皮较大减少了土壤的入渗速率，使坡面产流时间提前，结皮坡面产流时间明显早于无结皮坡面。结皮使得累积入渗量明显降低，雨强越大，结皮发育越充分，减渗作用越强。（6）应用Green-Ampt模型可较好的模拟结皮下的水分入渗过程，其最大相对误差为13.87%。研究结果为微地形条件下水蚀定量化的研究提供技术依据，对微地形径流、泥沙和物质迁移等的模拟计算具有重要参考意义。