黄土坡耕地地表糙度对产汇流的影响研究

Tillage and management practices have a significant effect on the surface roughness of cultivated soil. Surface roughness has an important effect on surface runoff, the convergence and direction of surface flow, and sediment yield from the bare surface of sloping fields. Understanding about the effect of surface runoff on runoff and the convergence of surface flow is the weakest part of runoff theory. Based on results of other researchers, this project was designed to study the effects of three cultivation methods (i.e., digging, hoeing, and contour tillage) on surface roughness, rainfall infilation, surface depression storage, and the path and process of convergent flow from a bare slope of loess-derived soil. The laws of soil infiltration and the characteristics of water reallocation were explained and a model for predicting surface depression storage was proposed. The characteristics and changes in the path of convergent flow path were clarified. The results were used to establish a model for the prediction of runoff from slopes.

研究表明，在水力侵蚀区的无作物覆盖的坡耕地上，由于耕作与管理形成的地表糙度会伴随着侵蚀过程，通过自身的消长与位移影响地表径流的产生、流向、汇流及产流、产沙量。而这些内容正是产汇流理论中研究比较薄弱部分。为此，本项目在分析前人研究成果的基础上，通过室内外人工模拟降雨实验，结合地统计学、ArcGIS和分形、分维、运动波与CA等理论与技术，探求裸露黄土坡耕地在人工掏挖、锄耕和等高耕作条件下，地表糙度对降雨入渗、填洼和径流汇集路径与过程影响的研究。最终阐明土壤入渗规律与水分再分配特征，提出填洼量预测模型，明晰汇流路径特征及变化。在此基础上，服务于坡面产汇流模型的构建。

研究表明，在水力侵蚀区的无作物覆盖的坡耕地上，耕作与管理形成的地表糙度对土壤侵蚀具有影响。为此，本项目在分析前人研究成果的基础上，通过室内外人工模拟降雨实验，结合数学，ArcGIS等理论与技术，开展裸露黄土坡耕地在人工掏挖、锄耕和等高耕作等条件下，地表糙度对降雨入渗、填洼和径流过程的影响。研究结果表明：（1）耕作与管理形成的地表糙度对土壤入渗过程具有显著影响。在粗糙坡面，垂直方向上入渗过程呈现从非均匀到均匀过渡的变化特征。粗糙坡面上降雨入渗率较整平坡面平均提高10%以上。（2）实施农业耕作措施的粗糙坡面平均填洼量是平整坡面2~5倍。但坡度对填洼量的影响较大。（3）在耕作后的坡耕地上，洼地和凸地是主要的土壤起伏元素。因此，以洼地和凸地为例，建立了以降雨强度，平均流速和洼地积水时间等参数为主的坡面产流模型。分析表明该模型能够较好的反映糙度对坡面产流的影响。以上结果表明，在坡耕地上，地表径流的产生与侵蚀过程受土壤入渗、地表填洼及汇流路径的影响较大，同时，地表糙度通过其对土壤入渗、地表填洼及产流的影响对坡耕地径流侵蚀过程具有调控作用。