Characteristics of Preferential Flow Under High-content Rock Fragment Purple Soil in the Three Gorges Reservoir Area
Dye tracing method was used to observe the occurrence of preferential flow under three kinds of land use patterns in Wangjiaqiao watershed in the Three Gorges Reservoir Area.Characteristics of preferential flow were obtained by figuring out the feature parameters of preferential flow.The results showed that the average volume content of rock fragment in different land use patterns was determined as follow:Garden land>forest land>farmland.The mean radius of soil macropores decreased with increase of soil depth.The maximum preferential flow depth of forest land was up to 60 cm and the dying zone was distinctly irregular.In the farmland,the dying zone mainly distributed in 0-15 cm soil depth and the dying area was smaller than forest land.There existed a large portion of bypassing flow in the farmland.The dying area of garden land occupied a large part of soil profile and the connectivity of preferential pathway was good.The number of staining pathway was determined as follow:Garden land>forest land>farmland.It demonstrated the higher preferential flow dyed pattern differentiation degree was observed in the garden land.The staining pathway of subsurface flow in purple soil was largely consisted of <20 mm staining pathway width.The type of subsurface flow was mainly low interaction macropore flow.The process of soil water movement was influenced by both rock fragment and soil macropores.
rock fragmentsoil macroporeland use patternpreferential flowpreferential pathway