Linking soil thickness and plot‐scale hydrological processes on the sloping lands in the Three Gorges Area of China: a hydropedological approach

Abstract

Abstract:The emerging interdisciplinary field of hydropedology promotes synergistic integration of pedology and hydrology to enhance the holistic study of soil-water interactions across space and time. Our study illustrated this integration, exemplifying from plotscale hydrological processes investigations on the sloping lands with different soil thickness in the Three Gorges Area of China. Our aims were to deal with (i) the watershed scale soil thickness survey, soil profiles description and hydrological processes inferential analysis for the plots with typical soil thickness from the pedological perspective, and (ii) the identification of dominant hydrological processes of these plots based on hydrological monitoring under simulated rainfall (designed as 60 mm h À1 ) from the hydrological perspective. The main results can be summarised as follows: (i) soil thickness of the sloping lands exhibited a wide range of variability along hillslopes. Thin soils reflected weaker pedogenesis degrees and less intense human intervention as compared with thick soils. (ii) Deep percolation and subsurface flow were the dominant processes in thin soils, whereas in thick soils, surface flow, deep percolation and storage were the dominant processes. (iii) Regarding to the surface flow, the 23-cm plot was mainly in the form of saturated overland flow, whereas the other plots were Horton overland flow. As to the subsurface flow, both 23-and 31-cm plots mainly took the form of preferential flow, the 59-and 76-cm plots mainly in the form of matrix flow regardless of soil horizon and the 45-cm plot displayed mainly the matrix flow in the A horizon and mainly the preferential flow in the AC horizon. Our study suggested that, relative to its parent disciplines of both pedology and hydrology, hydropedology improved synergies between pedology and hydrology in the plot-scale hydrological processes investigations.

Characteristics of the surface–subsurface flow generation and sediment yield to the rainfall regime and land-cover by long-term in-situ observation in the red soil region, Southern China

“…The lower subsurface flow on bare land was typically attributed to soil compaction by raindrops and an increased in the bulk density of the topsoil with time (Cassel et al, 1995;Truman et al, 2005). Rotted litter and roots loosened the topsoil and provided pathway for the formation of preferred flow, which was the most important component of the subsurface flow (Kramers et al, 2009;Fu et al, 2012;Zhang et al, 2014;Sheng et al, 2014).…”

“…A variety of approaches have been used to investigate subsurface flow, such as trench investigation (e.g., Kirkby, 1988) and hydrographic separation technique by natural isotopes (e.g., Sklash et al, 1986), which are commonly used in large-scale field investigations. The dye-tracer testing method (Nobles et al, 2010), time domain reflectometry (Fu et al, 2012) and ground penetrating radar (Leh et al, 2008) have been useful at the plot scale or in simulations. The results of subsurface flow during simulations or single rainfall events are greatly important for a deep understanding and model predictions; however, long-term, in-situ investigation provides data that more closely approximate the actual situation.…”

“…The results of subsurface flow during simulations or single rainfall events are greatly important for a deep understanding and model predictions; however, long-term, in-situ investigation provides data that more closely approximate the actual situation. Seasonally distinct rainfall patterns in a subtropical humid climate (Yin et al, 2014) and vertical soil layers in red soil that vary in their hydrological response cause the characteristics of subsurface flow to significantly differ from those of other regions, such as karst (Li et al, 2011) or purple soil region (Fu et al, 2012). In general, long-term field observations of surfacesubsurface flow generation have been relatively scarce in the red soil region, so more data were necessary for erosion and nonpoint source pollution control and water resources management.…”

“…However, the impact of rainfall regime on the subsurface flow was neglected in that research. The results from single rainfall events or simulated rainfall demonstrated that rainfall intensity and depth were the two main rainfall indexes that altered the subsurface flow (Fu et al, 2012;Xie et al, 2015). Research on the effect of rainfall regimes on subsurface flow loss is needed for a better understanding of hydrological-erosion processes due to rainfall.…”

Effects of vegetation cover and road-concentrated flow on hillslope erosion in rainfall and scouring simulation tests in the Three Gorges Reservoir Area, China

“…On considering the rainfall-runoff relationship for the long time conservation in a similar watershed Wangjiaqiao which located 8 km to the study area (Shi et al, 2004;Fang et al, 2012) and the rainfall simulation results by Fu et al (2011Fu et al ( , 2012 and Wang et al (2012), the rainfall simulations were applied to each plot for the duration of 60 min at the rainfall intensity of 90.0 mm h −1 (variation coefficient 6.3%) and 120 mm h −1 (variation coefficient 7.1%). The rainfall intensity was measured by five rain gauges (20 cm in diameter) that were distributed throughout the plot.…”