Abstract
Predicting the spatial distribution of soil moisture is an important hydrological question. We measured the spatial distribution of surface soil moisture (upper 6 cm) using an Amplitude Domain Reflectometry sensor at the plot scale (2 × 2 m) and small catchment scale (0.84 ha) in a temperate forest. The spatial variation of soil water content was higher during dry conditions than that during wet conditions. Results indicated 3.1 samples at the plot scale were sufficient to estimate mean soil water content when the precision was 0.1. Soil water content increased with increasing topographic index (TI) and soil-topographic index (STI) at the small catchment scale. The correlation between soil water content and TI was higher than that between soil water content and STI. This suggests that topography is more important for estimating surface soil moisture than soil depth as formation of surface soil moisture occurs at ≤6 cm.
Highlights
Variations in soil moisture affect hydrological processes such as evapotranspiration, transport of water and solutes in soils, and runoff response to rainfall
Soil moisture has been shown to decrease more rapidly with increasing root density in proximity to trees during dry spells [22]. These results suggest that preferential infiltration and pathways as well as variation of tree root uptake cause spatial heterogeneities in soil moisture content in forested catchments
Soil water content increased with increasing topographic index (TI) and soil-topographic index (STI) at the small catchment scale (0.84 ha)
Summary
Variations in soil moisture affect hydrological processes such as evapotranspiration, transport of water and solutes in soils, and runoff response to rainfall. Predicting the spatial and temporal distribution of soil moisture at the catchment scale is an important hydrological concern and it is affected by climate, topography, groundwater level, soil physical properties, and surface cover (vegetation) [1]. How to cite this paper: Noguchi, S., Tsuboyama, Y., Sidle, R.C. and Kubota, T. (2014) Spatial Distribution of Surface Soil Moisture in a Small Forested Catchment. S. Noguchi et al nious nature and mathematical simplicity [3]-[5]. TOPMODEL allows simulation of the spatial distribution of soil water content for each modeling time step. There has been no investigation of the relationship between these indices and soil moisture in forested catchments
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