Abstract
Rock fragments in soil strongly increase the complexity of hydrological processes. Spatial variability of preferential flow and infiltration characteristics, especially along a rocky-mountain hillslope are poorly understood. In this study, five rainfall–dye tracer experiments were performed in the rocky Taihang Mountains, northern China, to investigate the spatial variability of preferential flow and infiltration redistribution on different hillslope positions. Tracers were used to distinguish macropore flow and actual water flow patterns, and preferential flow indices and spatial non–uniformity of the infiltration redistribution were calculated using image analysis. Results showed increasing trends in the dye coverage, maximum infiltration depth, and steady infiltration rate with increased hillslope position, with a preferential flow fraction of 0.10, 0.11, 0.15, 0.29, and 0.26 for the bottom–, down–, mid–, upper–, and top–slope positions, respectively. With increased hillslope position, the spatial non–uniformity of the infiltration redistribution gradually increased in orthogonal and parallel directions to the stained section, and was supported by the fractal dimensions. Positive (gravel mass ratio, saturated water content, altitude, hydraulic conductivity and roots) and negative (bulk density and clay content) impacts on preferential flow and infiltration redistribution were quantitatively emphasized. The characteristic and mechanism of infiltration process were further identified along a rocky-mountain hillslope.
Highlights
Infiltration is an important process within the watershed water cycle, in which the soil absorbs, regulates, and transfers water to the soil layer under the combined actions of gravity and soil water forces [1,2]
A series of dye tracer experiments were performed at the bottom, lower, mid, upper, and top–slope positions of a typical rocky slope in the Taihang Mountains
The two different dye tracers were applied to mark the pattern of soil water infiltration and redistribution on the experimental rocky hillslope
Summary
Infiltration is an important process within the watershed water cycle, in which the soil absorbs, regulates, and transfers water to the soil layer under the combined actions of gravity and soil water forces [1,2]. Preferential flow plays an important role in the infiltration process. The non–equilibrium flow phenomenon, which penetrates through and bypasses most of the soil matrix and pores along some specific paths, widely exists in heterogeneous, anisotropic permeable media, especially in mountain areas with a complex geological structures [3,4]. In comparison to matrix connective flow, preferential flow is mainly driven by gravity and greatly decreases the contact time and area between the seepage liquid and solid media [5]. It is vital to have an effective buffer for the peak and duration of surface runoff [6,7] for the immediate replenishment of groundwater and required chemical composition [8,9], and to reduce the risks of soil erosion and landslides [10].
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