FACTORIAL KRIGING ANALYSIS OF SPRINGWATER CONTENTS IN THE DYLE RIVER BASIN, BELGIUM

This paper describes a geostatistical method, known as factorial krigi ng analysis, which is well suited for analyzing multivariate spatial i nformation. The method involves multivariate variogram modeling, princ ipal component analysis, and cokriging. It uses several separate corre lation structures, each corresponding to a specific spatial scale, and yields a set of regionalized factors summarizing the main features of the data for each spatial scale. The method is applied to springwater solute contents (Ca, Sr, Mg, K, Na, SO4, NO3 Cl, pH, electrical condu ctivity, alkalinity) measured in 86 springs situated in the Dyle River catchment area, Belgium. Two scales of spatial variation (1 and 9 km) are identified and interpreted. These correspond to local sources of contaminants due to human activities and regional changes in the geolo gic characteristics of the aquifer. At each scale, the correlation str ucture is analyzed and the regionalized factors are estimated by cokri ging and then mapped. The results are compared with those of a classic al multivariate approach, i.e., principal component analysis of the co rrelation matrix, which takes no account of the spatial location of th e observations.