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1.
The variability of hillslope form and function is examined experimentally using a simple model catchment in which most landscape development parameters are either known or controlled. It is demonstrated that there is considerable variability in sediment output from similar catchments, subjected to the same hydrological processes, and for which the initial hillslope profiles are the same. The results demonstrate that, in the case of catchments with a linear initial hillslope profile, the sediment output is initially high but reduces through time, whereas for a concave initial profile the sediment output was smaller and relatively constant. Concave hillslope profiles also displayed reduced sediment output when compared with linear slopes with the same overall slope. Using this experimental model catchment data, the SIBERIA landscape evolution model was tested for its ability to predict temporal sediment transport. When calibrated for the rainfall and erodible material, SIBERIA is able to simulate mean temporal sediment output for the experimental catchment over a range of hillslope profiles and rainfall intensities. SIBERIA is also able to match the hillslope profile of the experimental catchments. The results of the study provide confidence in the ability of SIBERIA to predict temporal sediment output. The experimental and modelling data also demonstrate that, even with all geomorphic and hydrological variables being known and/or controlled, there is still a need for long‐term stream gauging to obtain reliable assessments of field catchment hydrology and sediment transport. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

2.
Inadequate knowledge exists on the distribution of soil moisture and shallow groundwater in intensively cultivated inland valley wetlands in tropical environments, which are required for determining the hydrological regime. This study investigated the spatial and temporal variability of soil moisture along 4 hydrological positions segmented as riparian zone, valley bottom, fringe, and valley slope in an agriculturally used inland valley wetland in Central Uganda. The determined hydrological regimes of the defined hydrological positions are based on soil moisture deficit calculated from the depth to the groundwater table. For that, the accuracy and reliability of satellite‐derived surface models, SRTM‐30m and TanDEM‐X‐12m, for mapping microscale topography and hydrological regimes are evaluated against a 5‐m digital elevation model (DEM) derived from field measurements. Soil moisture and depth to groundwater table were measured using frequency domain reflectometry sensors and piezometers installed along the hydrological positions, respectively. Results showed that spatial and temporal variability in soil moisture increased significantly (p < .05) towards the riparian zone; however, no significant difference was observed between the valley bottom and riparian zone. The distribution of soil hydrological regimes, saturated, near‐saturated, and nonsaturated regimes does not correlate with the hydrological positions. This is due to high spatial and temporal variability in depth to groundwater and soil moisture content across the valley. Precipitation strongly controlled the temporal variability, whereas microscale topography, soil properties, distance from the stream, anthropogenic factors, and land use controlled the spatial variability in the inland valley. TanDEM‐X DEM reasonably mapped the microscale topography and thus soil hydrological regimes relative to the Shuttle Radar Topography Mission DEM. The findings of the study contribute to improved understanding of the distribution of hydrological regimes in an inland valley wetland, which is required for a better agricultural water management planning.  相似文献   

3.
Infiltration into frozen soil is a key hydrological process in cold regions. Although the mechanisms behind point‐scale infiltration into frozen soil are relatively well understood, questions remain about upscaling point‐scale results to estimate hillslope‐scale run‐off generation. Here, we tackle this question by combining laboratory, field, and modelling experiments. Six large (0.30‐m diameter by 0.35‐m deep) soil cores were extracted from an experimental hillslope on the Canadian Prairies. In the laboratory, we measured run‐off and infiltration rates of the cores for two antecedent moisture conditions under snowmelt rates and diurnal freeze–thaw conditions observed on the same hillslope. We combined the infiltration data with spatially variable data from the hillslope, to parameterise a surface run‐off redistribution model. We used the model to determine how spatial patterns of soil water content, snowpack water equivalent (SWE), and snowmelt rates affect the spatial variability of infiltration and hydrological connectivity over frozen soil. Our experiments showed that antecedent moisture conditions of the frozen soil affected infiltration rates by limiting the initial soil storage capacity and infiltration front penetration depth. However, shallow depths of infiltration and refreezing created saturated conditions at the surface for dry and wet antecedent conditions, resulting in similar final infiltration rates (0.3 mm hr?1). On the hillslope‐scale, the spatial variability of snowmelt rates controlled the development of hydrological connectivity during the 2014 spring melt, whereas SWE and antecedent soil moisture were unimportant. Geostatistical analysis showed that this was because SWE variability and antecedent moisture variability occurred at distances shorter than that of topographic variability, whereas melt variability occurred at distances longer than that of topographic variability. The importance of spatial controls will shift for differing locations and winter conditions. Overall, our results suggest that run‐off connectivity is determined by (a) a pre‐fill phase, during which a thin surface soil layer wets up, refreezes, and saturates, before infiltration excess run‐off is generated and (b) a subsequent fill‐and‐spill phase on the surface that drives hillslope‐scale run‐off.  相似文献   

4.
Hillslopes are thought to poorly record tectonic signals in threshold landscapes. Numerous previous studies of steep landscapes suggest that large changes in long‐term erosion rate lead to little change in mean hillslope angle, measured at coarse resolution. New LiDAR‐derived topography data enables a finer examination of threshold hillslopes. Here we quantify hillslope response to tectonic forcing in a threshold landscape. To do so, we use an extensive cosmogenic beryllium‐10 (10Be)‐based dataset of catchment‐averaged erosion rates combined with a 500 km2 LiDAR‐derived 1 m digital elevation model to exploit a gradient of tectonic forcing and topographic relief in the San Gabriel Mountains, California. We also calibrate a new method of quantifying rock exposure from LiDAR‐derived slope measurements using high‐resolution panoramic photographs. Two distinct trends in hillslope behavior emerge: below catchment‐mean slopes of 30°, modal slopes increase with mean slopes, slope distribution skewness decreases with increasing mean slope, and bedrock exposure is limited; above mean slopes of 30°, our rock exposure index increases strongly with mean slope, and the prevalence of angle‐of‐repose debris wedges keeps modal slopes near 37°, resulting in a positive relationship between slope distribution skewness and mean slope. We find that both mean slopes and rock exposure increase with erosion rate up to 1 mm/a, in contrast to previous work based on coarser topographic data. We also find that as erosion rates increase, the extent of the fluvial network decreases, while colluvial channels extend downstream, keeping the total drainage density similar across the range. Our results reveal important textural details lost in 10 or 30 m resolution digital elevation models of steep landscapes, and highlight the need for process‐based studies of threshold hillslopes and colluvial channels. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

5.
Field instrumentation was designed and installed to quantify the influence of forest interception on the spatial and temporal distribution of water flux onto and into the forest soil at the plot scale. An application is presented which demonstrates that the instrumentation has the required resolution to monitor the spatial variability and dynamics of the flux processes. The observations show that spatial variability of interception may play an important role, not only in small scale soil moisture heterogeneity, but also in the hydrological response of a forested catchment at the hillslope scale. They also highlight the need of gathering more field information on the effects of vegetation on the spatial variability of soil surface water input.  相似文献   

6.
Monitoring runoff generation processes in the field is a prerequisite for developing conceptual hydrological models and theories. At the same time, our perception of hydrological processes strongly depends on the spatial and temporal scale of observation. Therefore, the aim of this study is to investigate interactions between runoff generation processes of different spatial scales (plot scale, hillslope scale, and headwater scale). Different runoff generation processes of three hillslopes with similar topography, geology and soil properties, but differences in vegetation cover (grassland, coniferous forest, and mixed forest) within a small v‐shaped headwater were measured: water table dynamics in wells with high spatial and temporal resolution, subsurface flow (SSF) of three 10 m wide trenches at the bottom of the hillslopes subdivided into two trench sections each, overland flow at the plot scale, and catchment runoff. Bachmair et al. ( 2012 ) found a high spatial variability of water table dynamics at the plot scale. In this study, we investigate the representativity of SSF observations at the plot scale versus the hillslope scale and vice versa, and the linkage between hillslope dynamics (SSF and overland flow) and streamflow. Distinct differences in total SSF within each 10 m wide trench confirm the high spatial variability of the water table dynamics. The representativity of plot scale observations for hillslope scale SSF strongly depends on whether or not wells capture spatially variable flowpaths. At the grassland hillslope, subsurface flowpaths are not captured by our relatively densely spaced wells (3 m), despite a similar trench flow response to the coniferous forest hillslope. Regarding the linkage between hillslope dynamics and catchment runoff, we found an intermediate to high correlation between streamflow and hillslope hydrological dynamics (trench flow and overland flow), which highlights the importance of hillslope processes in this small watershed. Although the total contribution of SSF to total event catchment runoff is rather small, the contribution during peak flow is moderate to substantial. Additionally, there is process synchronicity between spatially discontiguous measurement points across scales, potentially indicating subsurface flowpath connectivity. Our findings stress the need for (i) a combination of observations at different spatial scales, and (ii) a consideration of the high spatial variability of SSF at the plot and hillslope scale when designing monitoring networks and assessing hydrological connectivity. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

7.
Information on the main drivers of subsurface flow generation on hillslopes of alpine headwater catchments is still missing. Therefore, the dominant factors controlling the water table response to precipitation at the hillslope scale in the alpine Bridge Creek Catchment, Northern Italy, were investigated. Two steep hillslopes of similar size, soil properties and vegetation cover but contrasting topography were instrumented with 24 piezometric wells. Sixty‐three (63) rainfall‐runoff events were selected over three years in the snow‐free months to analyse the influence of rainfall depth, antecedent moisture conditions, hillslope topographic characteristics and soil depth on shallow water table dynamics. Piezometric response, expressed as percentage of well activation and water peak magnitude, was strongly correlated with soil moisture status, as described by an index combining antecedent soil moisture and rainfall depth. Hillslope topography was found to be a dominant control only for the convex‐divergent hillslope and during wet conditions. Timing of water table response depended primarily on soil depth and topographic position, with piezometric peak response occurring later and showing a greater temporal variability at the hillslope bottom, characterized by thicker soil. The relationship between mean hillslope water table level and standard deviation for all wells reflected the timing of the water table response at the different locations along the hillslopes. The outcomes of this research contribute to a better understanding of the controls on piezometric response at the hillslope scale in steep terrain and its role on the hydrological functioning of the study catchment and of other sites with similar physiographic characteristics. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

8.
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9.
To evaluate the effects of hillslope topography on storm runoff in a weathered granite mountain, discharge rate, soil pore water pressures, and water chemistry were observed on two types of hillslope: a valley‐head (a concave hillslope) and a side slope (a planar hillslope). Hydrological responses on the valley‐head and side slope reflected their respective topographic characteristics and varied with the rainfall magnitude. During small rainfall events (<35 mm), runoff from the side slope occurred rapidly relative to the valley‐head. The valley‐head showed little response in storm runoff. As rainfall amounts increased (35–60 mm), the valley‐head yielded a higher flow relative to the side slope. For large rainfall events (>60 mm), runoff from both hillslopes increased with rainfall, although that from the valley‐head was larger than that from the side slope. The differences in the runoff responses were caused by differences in the roles of lower‐slope soils and the convergence of the hillslope. During small rainfall events, the side slope could store little water; in contrast, all rainwater could be stored in the soils at the valley‐head hollow. As the amount of rainfall increased, the subsurface saturated area of the valley‐head extended from the bottom to the upper portion of the slope, with the contributions of transient groundwater via lateral preferential flowpaths due to the high concentration of subsurface water. Conversely, saturated subsurface flow did not contribute to runoff responses, and the subsurface saturated area at the side slope did not extend to the upper slope for the same storm size. During large rainfall events, expansion of the subsurface saturated area was observed in both hillslopes. Thus, differences in the concentration of subsurface water, reflecting hillslope topography, may create differences in the extension of the subsurface saturated area, as well as variability in runoff responses. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

10.
In order to evaluate the relationship between the apparent complexity of hillslope soil moisture and the emergent patterns of catchment hydrological behaviour and water quality, we need fine‐resolution catchment‐wide data on soil moisture characteristics. This study proposes a methodology whereby vegetation patterns obtained from high‐resolution orthorectified aerial photographs are used as an indicator of soil moisture characteristics. This enables us to examine a set of hypotheses regarding what drives the spatial patterns of soil moisture at the catchment scale (material properties or topography). We find that the pattern of Juncus effusus vegetation is controlled largely by topography and mediated by the catchment's material properties. Characterizing topography using the topographic index adds value to the soil moisture predictions relative to slope or upslope contributing area (UCA). However, these predictions depart from the observed soil moisture patterns at very steep slopes or low UCAs. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

11.
Snowmelt water supplies streamflow and growing season soil moisture in mountain regions, yet pathways of snowmelt water and their effects on moisture patterns are still largely unknown. This study examined how flow processes during snowmelt runoff affected spatial patterns of soil moisture on two steep sub‐alpine hillslope transects in Rocky Mountain National Park, CO, USA. The transects have northeast‐facing and east‐facing aspects, and both extend from high‐elevation bedrock outcrops down to streams in valley bottoms. Spatial patterns of both snow depth and near‐surface soil moisture were surveyed along these transects in the snowmelt and summer seasons of 2008–2010. To link these patterns to flow processes, soil moisture was measured continuously on both transects and compared with the timing of discharge in nearby streams. Results indicate that both slopes generated shallow lateral subsurface flow during snowmelt through near‐surface soil, colluvium and bedrock fractures. On the northeast‐facing transect, this shallow subsurface flow emerged through mid‐slope seepage zones, in some cases producing saturation overland flow, whereas the east‐facing slope had no seepage zones or overland flow. At the hillslope scale, earlier snowmelt timing on the east‐facing slope led to drier average soil moisture conditions than on the northeast‐facing slope, but within hillslopes, snow patterns had little relation to soil moisture patterns except in areas with persistent snow drifts. Results suggest that lateral flow and exfiltration processes are key controls on soil moisture spatial patterns in this steep sub‐alpine location. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

12.
This paper presents the spatial and temporal variations of sheet flow and sediment transport on an agricultural field under natural rainfall. The study site is located in western France (Rennes, Brittany) where rainfall amount and intensity are moderate. It is a field of garden-peas presenting a convex–concave gentle slope where only sheet flow is observed. A network of simple, low-cost collectors is used to measure sheet flow and sediment transport along the slope and to estimate the spatial variability for a given position on the slope. The water and sediment discharge was measured for each rainfall event from February to June. The analysis of space and time variations according to the characteristics of the rainfall events, changes in vegetation and soil crusting shows that the sheet flow is low and the runoff coefficient decreases as the slope length increases. Infiltration is particularly active in concave parts of the hillslope whatever the characteristics of the rainfall events. Sediment transport decreases in time as the soil crusts and vegetation develops.  相似文献   

13.
Soil moisture state and variability control many hydrological and ecological processes as well as exchanges of energy and water between the land surface and the atmosphere. However, its state and variability are poorly understood at spatial scales larger than the fields (i.e. 1 km2) as well as the ability to extrapolate field scale to larger spatial scales. This study investigates soil moisture profiles, their spatial organization, and physical drivers of variability within the Walnut Creek watershed, Iowa, during Soil Moisture Experiment 2005 and relates the watershed scale findings to previous field‐scale results. For all depths, the watershed soil moisture variability was negatively correlated with the watershed mean soil moisture and followed an exponential relationship that was nearly identical to that for field scales. This relationship differed during drying and wetting. While the overall time stability characteristics were improved with observation depth, the relatively wet and dry locations were consistent for all depths. The most time stable locations, capturing the mean soil moisture of the watershed within ± 0·9% volumetric soil moisture, were typically found on hill slopes regardless of vegetation type. These mild slope locations consistently preserve the time stability patterns from field to watershed scales. Soil properties also appear to impact stability but the findings are sensitive to local variations that may not be well defined by existing soil maps. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

14.
Hillslope hydrological modelling is considered to be of great importance for the understanding and quantification of hydrological processes in hilly or mountainous landscapes. In recent years a few comprehensive hydrological models have been developed at the hillslope scale which have resulted in an advanced representation of hillslope hydrological processes (including their interactions), and in some operational applications, such as in runoff and erosion studies at the field scale or lateral flow simulation in environmental and geotechnical engineering. An overview of the objectives of hillslope hydrological modelling is given, followed by a brief introduction of an exemplary comprehensive hillslope model, which stimulates a series of hydrological processes such as interception, evapotranspiration, infiltration into the soil matrix and into macropores, lateral and vertical subsurface soil water flow both in the matrix and preferential flow paths, surface runoff and channel discharge. Several examples of this model are presented and discussed in order to determine the model's capabilities and limitations. Finally, conclusions about the limitations of detailed hillslope modelling are drawn and an outlook on the future prospects of hydrological models on the hillslope scale is given.The model presented performed reasonable calculations of Hortonian surface runoff and subsequent erosion processes, given detailed information of initial soil water content and soil hydraulic conditions. The vertical and lateral soil moisture dynamics were also represented quite well. However, the given examples of model applications show that quite detailed climatic and soil data are required to obtain satisfactory results. The limitations of detailed hillslope hydrological modelling arise from different points: difficulties in the representations of certain processes (e.g. surface crusting, unsaturated–saturated soil moisture flow, macropore flow), problems of small‐scale variability, a general scarcity of detailed soil data, incomplete process parametrization and problems with the interdependent linkage of several hillslopes and channel–hillslope interactions. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

15.
Vegetation has a major influence on the water and energy balance of the earth's surface. In the last century, human activities have modified land use, inducing a consequent change in albedo and potential evapotranspiration. Linear vegetation structures (hedgerows, shelterbelts, open woodland, etc) were particularly abundant but have declined considerably over the past several decades. In this context, it is important to quantify their effect on water and energy balance both on a global scale (climate change and weather prediction) and on a local scale (soil column, hillslope and watershed). The main objective of this study was to quantify the effect of hedgerows on the water cycle by evaluating spatial and temporal variations of water balance components of a hillslope crossed by a hedgerow. Water flow simulation was performed using Hydrus‐2D to emphasize the importance of transpiration in the water balance and to evaluate water extraction from groundwater. Model validation was performed by comparing simulated and observed soil matrix potentials and groundwater levels. Hedgerow transpiration was calculated from sap flow measurements of four trees. Water balance components calculated with a one‐dimensional water balance equation were compared with simulations. Simulation runs with and without tree root uptake underlined the effect of hedgerow transpiration, increasing capillary rise and decreasing drainage. Results demonstrated that the spatial and temporal variability of water balance components was related to the hedgerow presence as well as to the meteorological context. The relations between transpiration, groundwater proximity and soil‐water availability determined the way in which water balance components were affected. Increased capillary rise and decreased drainage near hedges were related to the high transpiration of trees identified in this study. Transpiration reached twice the potential evapotranspiration when groundwater level and precipitation amounts were high. Water balance analysis showed that transpiration was a substantial component, representing 40% of total water output. These results may offer support for improving hydrological models by including the effect of land use and land cover on hydrological processes. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

16.
As a fundamental unit of the landscape, hillslopes are studied for their retention and release of water and nutrients across a wide range of ecosystems. The understanding of these near‐surface processes is relevant to issues of runoff generation, groundwater–surface water interactions, catchment export of nutrients, dissolved organic carbon, contaminants (e.g. mercury) and ultimately surface water health. We develop a 3‐D physics‐based representation of the Panola Mountain Research Watershed experimental hillslope using the TOUGH2 sub‐surface flow and transport simulator. A recent investigation of sub‐surface flow within this experimental hillslope has generated important knowledge of threshold rainfall‐runoff response and its relation to patterns of transient water table development. This work has identified components of the 3‐D sub‐surface, such as bedrock topography, that contribute to changing connectivity in saturated zones and the generation of sub‐surface stormflow. Here, we test the ability of a 3‐D hillslope model (both calibrated and uncalibrated) to simulate forested hillslope rainfall‐runoff response and internal transient sub‐surface stormflow dynamics. We also provide a transparent illustration of physics‐based model development, issues of parameterization, examples of model rejection and usefulness of data types (e.g. runoff, mean soil moisture and transient water table depth) to the model enterprise. Our simulations show the inability of an uncalibrated model based on laboratory and field characterization of soil properties and topography to successfully simulate the integrated hydrological response or the distributed water table within the soil profile. Although not an uncommon result, the failure of the field‐based characterized model to represent system behaviour is an important challenge that continues to vex scientists at many scales. We focus our attention particularly on examining the influence of bedrock permeability, soil anisotropy and drainable porosity on the development of patterns of transient groundwater and sub‐surface flow. Internal dynamics of transient water table development prove to be essential in determining appropriate model parameterization. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

17.
Field capacity is a commonly used soil parameter in surface water hydrological models, loosely defined as the moisture content of a soil after drainage. The most commonly applied expression for field capacity is defined as the remaining water in a vertical soil column subject to 1/3 atm. of pressure head. While this quantification is sufficient in some cases, the definition is not consistent with the use of bulk field capacity in calculations of lateral drainage from hillslopes, as required by some surface soil parameterizations, nor does it address additional complications arising from differences in soil texture or sample size. Here, a simple alternative expression for bulk field capacity in a sloping or vertical soil is derived directly from Richards equation with the use of the Brooks‐Corey characteristics. It is demonstrated that this expression is consistent with data acquired from vertical soil columns, but may be extended to additional situations commonly found in surface water models and land surface schemes. The calculation of bulk field capacity requires only the Brooks‐Corey pore size distribution index, soil air‐entry pressure, and hillslope length and slope, and may be considered a physically based alternative to pedotransfer function or lookup table approaches. Copyright © 2010 John Wiley & Sons Ltd and Crown in the right of Canada.  相似文献   

18.
Surface soil moisture content exhibits a high degree of spatial and temporal variability. The purpose of this study was (a) to characterize variations in moisture content in the 0–5 cm surface soil layer along a hillslope transect by means of intensive sampling in both space and time; and (b) to make inferences regarding the environmental factors that influence this variability. Over a period of seven months, soil moisture content was measured (gravimetric method) on a near-daily basis at 10 m intervals along a 200 m downslope transect at the Rattlesnake Hill field site in Austin, Texas. Results indicate that significant variability in soil moisture content exists along the length of the transect; that variability decreases with decreasing transect-mean moisture content as the hillslope dries down following rain events; and that the dominant influences on moisture content variability are dependent upon the moisture conditions on the hillslope. While topographic and soil attributes operate jointly to redistribute soil water following storm events, under wet conditions, variability in surface moisture content is most strongly influenced by porosity and hydraulic conductivity, and under dry conditions, correlations are strongest to relative elevation, aspect and clay content. Consequently, the dominant influence on soil moisture variability gradually changes from soil heterogeneity to joint control by topographic and soil properties as the transect dries following significant rain events.  相似文献   

19.
The connectivity and upscaling of overland runoff and sediment transport are important issues in hillslope hydrology to identify water flux and sediment transport within landscape. These processes are highly variable in time and space with regard to their interactions with vegetation and soil surface conditions. The generation of overland runoff and its spatial connectivity were examined along a slope to determine the variations in the transport mechanism of runoff and soil particles by rain splash and overland runoff. Field experiments were conducted by erosion plots on a steep hillslope at lengths of 5, 10, and 15 m. The overland runoff connectivity and flow transport distance decreased with the slope length, while spatial variability of infiltration increased significantly with the slope length. Observation of subsurface flow revealed that surface soil and litter layer could have important role in water transport. However, the surface soil water content and water flux transport along the slope was highly variable for different storm events; the variability was related to the complexity of the system, mainly by way of the initial wetness conditions and infiltration characteristics. Only net rain‐splashed soil was measurable, but examination of the water flux, overland runoff and sediment transport connectivity, characteristics of sheetwash, and the variability in spatial infiltration indicated an increase in the contribution of the rain splash transport mechanism along the slope. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

20.
Surface soil moisture has been extensively studied for various land uses and landforms. Although many studies have reported potential factors that control surface soil moisture over space or time, the findings have not always been consistent, indicating a need for identification of the main factors. This study focused on the static controls of topographic, soil, and vegetation features on surface soil moisture in a steep natural forested headwater catchment consisting of three hillslope units of a gully area, side slope, and valley‐head slope. Using a simple correlation analysis to investigate the effects of the static factors on surface soil moisture at depths of 0–20 cm at 470 points in 13 surveys, we addressed the characteristics of surface soil moisture and its main controlling factors. The results indicated that the mean of surface soil moisture was in the decreasing order of gully area > valley‐head slope > side slope. The relationship between the mean and standard deviation of surface soil moisture showed a convex‐upward shape in the headwater catchment, a negative curvilinear shape in the gully area, and positive curvilinear shapes at the side and valley‐head slopes. At the headwater catchment and valley‐head slope, positive contributions of soil porosity and negative contributions of slope gradient and saturated hydraulic conductivity were the main controlling factors of surface soil moisture under wetter conditions, whereas positive contributions of topographic wetness index and negative contributions of vegetation density were the main controlling factors of surface soil moisture under drier conditions. At the side slope underlain by fractured bedrocks, only saturated hydraulic conductivity and vegetation density were observed to be the controlling factors. Surface soil moisture in the gully area was mainly affected by runoff rather than were static features. Thus, using hillslope units is effective for approximately estimating the hydrological behaviours of surface moisture on a larger scale, whereas dependency between the main static factors and moisture conditions is helpful for estimating the spatial distributions of surface moisture on a smaller scale.  相似文献   

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