Spatial variability in soil moisture as predicted from airborne thematic mapper (ATM) data

Abstract

In the first part of this project, the extent to which moisture content of alluvial soils could be predicted from imagery derived from an airborne thematic mapper (ATM) was investigated. From sampling done on the same day as the flight, it was found that digital numbers derived from the thermal channel (waveband 11) were strongly correlated with gravimetric moisture content. From sampling three fields of contrasting land cover, the relationship between waveband I 1 values and moisture content was found to be independent of land cover type. Spatial va-iation in waveband 11 values and thus moisture content were related to palaeochannel patterns on the alluvial land. This was investigated by deriving variograms for long transects from each of the three investigated fields. The range and sills of the variograms are shown to express the nature and pattern of palaeochannels. By the application of such geostatistical techniques, high resolution imagery can thus be used to quantify palaeochannel characteristics on alluvial land.

Geostatistical analysis of soil moisture variability on Da Nangou catchment of the loess plateau, China

“…Our results indicated that the sills increased with depth below 5 cm, but that the ranges did not show any other patterns with depth during observation period. Because the range value can be used as a guide to indicate the size of areas of different moisture contents and spatial frequency of soil moisture changes (Davidson and Watson 1995), soil moisture change patterns of the subsurface are different to those of the surface in our study. This implies that the connectivity of subsurface pathways may be quite different when compared to the connectivity of hydrological pathways at the surface.…”

“…Other reported ranges have been as small as 6 m (Hawley and others 1983) and as large as 3,500 m (Hollenbeck and others 1996). No consensus on spatial dependence, and differences in ranges of 6±3,500 m suggest that soil moisture is a time-dependent property and thus there is the possibility of changing spatial dependence (Davidson and Watson 1995). Therefore, in order to assess the spatio-temporal structure of soil moisture comprehensively, further investigation is required in various locations, at various depths, and over a large range of scales.…”

Airborne remote sensing of valley floor geoarchaeology using Daedalus ATM and CASI

“…In geographical contexts, the techniques have been used to characterize the physical properties of soils, sediments and vegetation (e.g. Davidson and Watson, 1995;Rainey et al, 2003;Harris et al, 2005) and such studies are directly analogous to those undertaken by archaeologists' (e.g. Ben-Dor et al, 2002;Liu et al, 2003).…”

Dealing with soil variability: some insights from land degradation research in central Spain

“…Such spatially non-uniform runoff has been related to several variables including the patchiness of vegetation cover (Cerda, 1995;Bergkamp et al, 1996;Nicolau et al, 1996), differences in soil moisture (Fitzjohn et al, 1998), differences in lithology (Lavee and Yair, 1990), water repellency (Irneson et aI., 1992), surface roughness (Lavee et al, 1995) and soil crusting (Bromley et al, 1997). These 'source' and 'sink' areas can be delimited into units based on their differing hydrological response and spatial limits which can be defined from the variogram (Davidson and Watson, 1995). Since these units display a different runoff response they can be termed 'hydrological response units'.…”

“…One of the land uses studied was a ploughed field located in a valley bottom with a Davidson and Watson, 1995). A fundamental tool necessary for geostatistical analysis is the variogram (Figure 2) (Journel and Huijbregts, 1978).…”