FIELD EXPERIMENTS AND FINDINGS ON THE RELATIONSHIP OF INFILTRATION AND RUNOFF WITH RAINFALL ON FOREST GRANITIC SLOPE AT THREE GORGES OF YANGTZE RIVER

Based on the measured data in the field and according to the form and energy of soil water,the mechanism of the rainfall infiltration in the surface of the granite forestland of Three Gorges area was studied.The results showed that when the rainfall intensity was larger than soil infiltration rate and soil water did not reach the largest capillary water volume,preferential flow appeared.It appeared earlier than infiltrated soil water flow.When the rainfall intensity was smaller than soil infiltration rate,and there was no water accumulated in the surface,infiltrated soil water flow appeared earlier than preferential flow.From the flow process of infiltrated soil water,it can be seen that the infiltrated soil water flow appeared earlier than the preferential flow when there was no water accumulated in the surface,and that the preferential flow appeared earlier than the infiltrated soil water flow when there was water accumulated in the surface and the soil water did not reach the biggest capillary water volume.In both conditions,the peak of preferential flow appeared earlier than that of infiltrated soil water flow.