Studying the spatial structure evolution of soil water content using multivariate geostatistics

Soil water content varies widely in space and time as the soil is wetted by rain, drained by gravity and dried by evaporation and root extraction. Consequently there has been increased interest in modelling and measuring soil water content evolution at varying spatial scale. The objective of this study was to examine the utility of multivariate geostatistical models for characterising the spatio-temporal variability of soil water content. This approach uses the set of t sampled times as a realisation of t correlated random functions. Estimation of soil water content involved fitting an anisotropic linear model of coregionalization to the t(t+1)/2 simple and cross variograms consisting of four spatial structures: a nugget effect, an isotropic structure and two anisotropic structures in E–W and N–S directions. Variography revealed a high temporal correlation between the soil water contents measured at different times, declining as the interval between the observations increases. The autumn rain events on dry soil produced an erratic distribution pattern of water in the soil. Inspection of the cokriged maps of soil water revealed the dynamics of soil water redistribution owing to evapotranspiration or rainfall.