Three-dimensional spatial variability of hydraulic conductivity in the Choushui River alluvial fan, Taiwan

This work adopted the geostatistical method, ordinary kriging, to determine the three-dimensional (3-D) spatial variability and distribution of hydraulic conductivity (K) in the Choushui River alluvial fan, Taiwan. The spatial distributions of estimated K obtained using two 3-D estimation approaches, including the non-stratified estimation and the stratified estimation, were statistically evaluated. Moreover, the vertical (small-scale) and horizontal (large-scale) variations were anisotropically analyzed and their relationship to the hydrogeological formation of aquifers was examined. A cross-validation procedure indicates that the realization of the non-stratified estimation yields fewer estimated errors than the stratified estimation. The directions of maximum continuity for horizontal K variability of all aquifers range from N60°W to N105°W, and are consistent with the current flow direction of the rivers and the ancient river shift in the Choushui River alluvial fan. The anisotropic analysis indicates that the hydrogeological parameters of the aquifers are spatially correlated with the formation environment of the Choushui River.