【作者】 程金花；

【导师】 张洪江；

【作者基本信息】 北京林业大学 ， 水土保持与荒漠化防治， 2005， 博士

【摘要】 优先流是一种快速非平衡的土壤水分运动,优先流现象极大地影响了坡面地表径流及地下径流的形成和运动过程,作为土壤水分一种特殊运动形式,优先流是当今世界水文学研究的重点和难点问题之一。 本文主要以长江三峡库区林地坡面优先流为研究对象,以湖北省秭归县曲溪小流域为试验基地,选择曲溪小流域内典型林地坡面,采用剖面灌水法分析了优先路径在土壤剖面上的水平分布和垂直分布特性、优先流运动特征、影响优先流的因子、优先流对剖面渗流和地表径流的影响。在此基础上,修正了优先流模型。得出主要结论如下: (1)优先流是长江三峡花岗岩区林地坡面的一种普遍现象,观测的优先流雷诺数均大于10,说明优先流运动不遵从达西定律。在该地区存在两种类型的优先路径,即地质型优先路径(原生型优先路径)和生物型优先路径(次生型优先路径)。优先路径主要分布在距地表以下0.8～1.0m范围内,在土层中的分布呈聚集状分布,其拥挤度为6.0～19.0,优先路径的平均密度为5～7个/m。 (2)优先流产流过程表现为明显的涨水、峰值和退水3个阶段。涨水历时较短,退水历时较长。长江三峡花岗岩地区优先流产流滞后降雨时间为5～95.5h,优先流历时为7～170h。优先流产生后,峰值流量出现时间为产流后1～13h,大部分场降雨产生的优先流在产流后1～2h就达到峰值流量。当前期降雨(3～7日降雨量)充分后,只要再有较小的降雨,都可能产生优先流。 (3)降雨和土壤物理特性是影响优先流的重要因子,影响优先流流量的主要降雨因子是降雨总量,两者呈现出极显著的正相关关系;影响优先流历时的主要降雨因子是降雨历时和降雨总量,优先流历时与降雨历时为极显著正相关关系,与降雨总量为显著正相关关系;影响优先流峰值流量的主要降雨因子是降雨总量,两者为显著正相关关系。优先流滞后降雨的时间与降雨各因子线性关系均不显著。>20mm/h降雨量和最大降雨强度与优先流各因子均不存在显著性相关关系。试验地不同土层之间土壤物理性质差异较大,不同土层土壤物理性质的显著差异导致土壤水分运动中产生侧向优先流。 (4)优先流流量占剖面渗流总量的比例可达2.40%～48.72%,其水分通量最大可达剖面渗流水分通量的17200倍。这说明优先流对降雨的快速入渗有较大作用,能够加速渗流流动速度,会在很大程度上增加土壤水分运动通量。该结果与国外研究结果较为一致。 (5)同等降雨及下垫面条件下,受降雨量影响,对应的优先流总量和坡面径流总量呈一元线性正相关关系,回归方程为:更多还原

【Abstract】 Abstract: Preferential flow is a kind of non-equilibrium movement of soil water. It influenced greatly on the formation and movement of surface runoff and underground (subsurface) runoff. As a kind of special movement form of soil water, preferential flow is one of the most important and difficult problems in current research about hydrology.In this paper, the Quxi watershed of Zigui county, Hubei province, was selected as the experimental site. In a slope of forestland, the distribution characteristics of preferential flow were analyzed by the method of irrigating. The moving characteristics of preferential flow, the factors influencing preferential flow, and the effect of preferential flow on infiltrated flow and surface runoff were also analyzed. Based on that, the preferential flow model was modified. The main conclusions were as the following:(1) Preferential flow is very common in the granite area of the Three-Gorges, Yangtze River. Its Re is bigger than 10, which shows that the movement of preferential flow does not follow Darcy-Law. There exist two kinds of preferential paths in this area, namely original preferential paths and secondary preferential paths. Preferential paths mainly exist in the soil layer of 0.8~1.0m under ground, which is gatherly distributed with index of 6.0-19.0. The mean number of existed preferential paths is 5~7/m.(2) The process of preferential flow is obviously divided into 3 phases: increasing phase, peak, and decreasing phase. Its increasing phase is very short, while decreasing phase is very long. Normally, preferential flow appeared 5-95.5h later than precipitation. Its duration time is 7-170h. Most preferential flow reach their peak l~2h after their appearance. In the condition of abundant antecedent rainfall, preferential flow will appear even with little precipitation.(3) Precipitation and soil characteristics are the most important factors influencing preferential flow. The main factor influencing the amount of preferential flow is the amount of rainfall, which is evidently positively related to the amount of preferential flow. The main factors influencing the duration of preferential flow are the duration and the amount of rainfall. The duration of preferential flow is very evidently positively related to the duration of rainfall, and evidently positively related to the amount ofrainfall. The main factor influencing the peak of preferential flow is the amount of rainfall, which is evidently positively related to the peak of preferential flow. The soil characteristics of different soil layers are very different, which induced the lateral preferential flow.(4) The ratio of preferential flow to infiltrated flow may reach 2.4%~48.72%. Its shuifentongliang may be 17200 times of that of infiltrated flow, which shows that preferential flow has great effect on the quick infiltration of precipitation. Preferential flow could increase the moving velocity of infiltrated flow and increase the shuifentongliang of soil water in a great extent.(5) Comparing the amount of preferential flow and amount of surface runoff, it is found that they have the positively linear related relationship. The equation is as the following:y = 0.7761x + 0.0379 (R2=0.8294, R=0.9107)In one rainfall, the more the amount of preferential flow is, the more the amount of surface runoff is. So do the inverse situation. In one rainfall, the increase of the amount of preferential flow induced the decrease of the amount of surface runoff. The appearance of preferential flow delayed the appearing time of the peak of surface runoff, increased the increasing duration of surface runoff, and prolonged the total duration of surface runoff.(6) Based on the data measured in lab and in the field, the preferential flow model is set up as the following equation:The simulated value matched better with measured value in surface soil than it does in deep layers. The simulated results showed that the effective path-length is 150mm in the soil layer 83-110cm, the longest of all the soil layers, which meant that pre更多还原