Abstract
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 transectmean 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.
Highlights
Soil moisture stored near the land surface affects a wide variety of earth system interactions over a range of spatial and temporal scales
Because of the ease with which relative elevation is measured we suggest that its utility as a predictive index of surface moisture content be explored beyond the context of Rattlesnake Hill
Variability in surface soil moisture content was studied along a 200 m downslope transect on a hillslope in central Texas
Summary
Soil moisture stored near the land surface affects a wide variety of earth system interactions over a range of spatial and temporal scales. Given the importance of surface soil moisture to earth system processes, quantification of its spatial– temporal behavior is receiving increased attention from the hydrologic community (e.g. from the scale of hillslopes and small watersheds (Western et al, 1997) to the global scale (IGPO, 1995)). This task is not trivial since surface soil moisture. The emphasis of this review is on field investigations of near-surface (0–15 cm) soil moisture variability at small spatial scales (plot to small watershed scale). Slope orientation, influences solar irradiance and evapotranspiration and soil moisture. Reid (1973) found a significant correlation between aspect and soil moisture content
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