Spatial distribution of soil moisture in a small catchment. Part 1: Geostatistical analysis

Soil moisture measurements were performed weekly at about 60 locations in a small catchment (6.3 km(2)) in southwest Germany over a period of 6 years. The measurements were carried out by using time domain reflectometry at four different depths. The data was analyzed and a time independent semivariogram was derived. For interpolation, five different methods, ordinary kriging, external drift kriging, indicator kriging, external drift indicator kriging and Bayes-Markov updating were used. Additional information such as topographical parameters derived from a digital elevation model, were used to improve the estimation in the external drift methods. In the Bayesian case, even qualitative information such as land use could be used. Depending on the assumptions, the interpolated maps differed significantly. The performance of the different methods was compared using a cross-validation approach. The results indicate improvement in the interpolation quality by using the topographic index or land use as additional information. (C) 1998 Elsevier Science B.V. All rights reserved.