Influence Of Pipe Flow To Surface Runoff In Granite Region Within Three-Gorges Of Yangtze River

Preferential flow is used for describing term of non-equilibrium process that takes place under many kinds of environmental condition, being as a kind of special movement form of soil moisture, the preferential flow is focal point and one of difficult point problems that the hydrology is studied in current world. This text has been summed up to concept, classification, research approach of preferential flow, etc. on the basis of a great amount of consultable literatures. Regarding Quxi small watershed of Zigui County in Hubei province as trial base, pipe flow and soil infiltration flow to flow meter have been introduced and observed by itself through the soil section, the preferential flow, slope surface flow, soil infiltration flow, and the total surface flow of watershed have been observed under observed natural rain process and its influence by the method of observing slope surface flow, the total surface flow, natural rain through flow district,triangular weir and digital rain meter; flow theory, path, influence factor of preferential flow and the influence of preferential flow to the process of surface runoff are analyzed under the specific regional condition in granite region within Three-Gorges of Yangtze River. The main conclusions achieved are as follows:(1) Preferential flow is a common phenomenon in the granite region of the Three Gorges in the Yangtze River. The observed Renault quantity of pipe flow is averagely bigger than 10, on the other hand, the observed Renault quantity of soil infiltration flow is averagely smaller than 10. According to the classification system of Kitahara Hikalu, the preferential flow predominated to the pipe flow as a main type can not follow to Darcy Law. Two kinds of soil pipe exist in the granite region of the Three-Gorges in the Yangtze River, which are the biological pipes formed by dead plant roots and the geological pipesformed by soil cracks. The result of field observation shows that the soil pipes concentrate mainly nearby the transitional zone forming distribution with assembling type between weathering of granite layer and the semi-weathering of granite layer, where is about deep 1.2 -1.6 m under the ground surface, and density of the soil type is about 5-7 pieces per meter.(2) Hydrology wave shape of pipe flow is similar basically, shown obviously 3 stages that are rising, peak value and retreating, and it lasts short to rise as well as lasts long to fall. In the granite region of Three Gorges in Yangtze River, the pipe flow's quantity of single soil pipe is about 0.00036-0.17918 m3, the average peak quantity is about 120-25000 cm3/h. The pipe flow is significantly influenced by precipitation and rainfall intensity, meanwhile at the same condition of rainfall, linear interrelation between the quantity of pipe flow and rainfall is obvious, the equation is:y= 0.0035x-0.1105 (R=0.9405).Quantity wave of the preferential flow is positively related to changes of the rainfall intensity, moreover, the pipe flow is sensitive to the micro-changes of rainfall during the rainfall period, and micro-change of intensity of rainfall will be distinctly reflected in pipe flow's hydrological graph, especially, it may make pipe flow's hydrological graph downtrend, or cause small bounce.(3) The ratio of the total amount of the sectional influent to the pipe flow is 8.70%-22.11%, among the rainfall process, the quantity of the pipe flow is linear positively interrelated to the relation of total amount of soil infiltration flow, the general relational equation is:y= 30.58x +7.42 x10^-3 (the rainfall NO.20020528, R=0.812)(4) Under the condition of equal rainfall and ground, the quantity of pipe flow is linear positively interrelated to relation to corresponding surface runoff in slope, the general equation is:y = 0.7761x+ 0.0379 (R=0.9107)(5) The percentage ratio of the quantity of pipe flow covering total runoff quantity ofthe watershed is 0.53%².31%. During the raining process, the total quantity of pipe flow and total quantity of the runoff in the watershed assumes...