【作者】 杨超；

【导师】 雷廷武；

【作者基本信息】 中国农业大学 ， 水土保持与荒漠化防治， 2005， 硕士

【摘要】 支离破碎的黄土高原可以由不同大小的(小)流域组成,是黄河泥沙的主要来源区。研究小流域产流产沙过程和机理,可深入理解小流域土壤侵蚀的时空分布规律,为小流域侵蚀预报模型研究和水土流失防治提供思路和数据,为此,在室内构建的投影面积65.9m~2的模型上进行了流域人工降雨侵蚀试验。 利用中国科学院水土保持研究所降雨大厅内建立的模型流域进行研究。为精确描述小流域地貌,自制了高程测量仪,对流域模型高程进行0.1m×0.1m测量,用GIS软年生成模型流域的DEM。处理所得DEM与原模型流域地形特征点数据比较误差范围为±0.005m,通过流域降雨侵蚀前后高程的对比,得到室内小模型流域的侵蚀分布。 研究了不同雨强和降雨历时下的流域产流及产沙过程,采用的雨强为:25、50、75、100mm/hr,降雨历时为:5、10、20、40 min。采用传感器测量流域及其分支沟道山口的含沙量变化过程,采用量水堰和水位传感器测量相应点的流量过程,采用薄层水流流速传感器测量沿沟道的水流流速。试验结果表明:(1)产流过程与雨强和降雨历时的关系为:随着雨强的增加,起流过程变得陡峭,产流过程线的峰值与雨强成比例,降雨历时在室内模型降雨产流上更多地表现为产流平稳段时间拉长;(2)产沙过程与雨强和降雨历时的关系为:水流含沙量随雨强的增加而增大,在小雨强时含沙量随降雨历时有增加的趋势;(3)产流与产沙的耦合关系为:在起流阶段产流产沙过程具有很好的一致性;(4)沟道流速随雨强的增加而增加,降雨历时对沟道流速的影响不显著。 室内模型流域试验揭示了小流域的产流产沙过程、流域侵蚀发育过程利侵蚀分布,为土壤侵蚀机理研究提供了室内可控实验系统,对预测土壤侵蚀模型研究和预防水土流失具有一定的科学指导作用。更多还原

【Abstract】 The Loess Plateau was morphologically formed with various small watersheds, which deliver enormous sediments into the Yellow River. The studies on the erosion mechanism and runoff and sedimentation processes is of great significance to the prediction of soil and water losses and to the implementations of soil and water conservational practices.A series of laboratory rain simulation experiments were conducted at the State Key Laboratory of Soil Erosion and Dry-land Farming on the Loess Plateau, Chinese Academy of Sciences, with a watershed model of 66 m2. To accurately present the watershed, a special device was developed to measure the topographic elevation of the watershed at a resolution of 0.1 by 0.1 m. The DEM of the watershed was generated with GIS software. Comparison of the representative points of the watershed with the measured data found the accuracy of the measurements to be ±0.005 m. The difference between the elevations before and after a rainfall event was used to estimate the soil erosion distribution in the watershed.The runoff and sedimentation processes were investigated under different rainfall intensities and durations, with rainfall intensities at 25, 50, 75 mm/hr and at durations of 5, 10, 20 and 40 min. Sediment sensors were used to measure the suspended sediment concentrations (process) at the outlets of the watershed and the branch channels. Weirs and water level sensors were used to measure the runoff processes at the same locations where sediment measurements were taken. The flow velocities in the channels were measured with the sensors for shallow water flow velocity. The results indicated that with increase in rainfall intensity, faster increase in runoff was induced and the peak runoff volume was proportional to the rainfall intensity, and longer rainfall duration was associated with prolonged stable runoff. Sediment concentration increased with rainfall intensity, with continuous increase trend with time under lower rainfall intensity. The runoff processes were well coupled with the runoff processes. The flow velocities at the stable stage in the channels increased with rainfall intensity, with no significant influences from the rainfall duration.The investigation presents the runoff, sedimentation, erosion development processes and erosion distribution, which supplies a controllable experimental system for the study on watershed erosion mechanism, which is of great importance to watershed erosion model and soil and water conservation practices.更多还原