Estimating Hydraulic Conductivities in an Alluvial Basin from Sediment Facies Models

Abstract

Abstract It is not uncommon that hydraulic conductivity data are sparse in an area, and that information about subsurface sediment distributions are even more sparse or of poor quality. It is therefore desirable to have rational ways to estimate conductivity distributions for ground‐water flow modeling. Interpretations of the geologic history of a fault‐bounded sedimentary basin in south Santa Clara County, California, were used to estimate variations in sediment distribution and resulting relative hydraulic conductivities. Spatial sediment distributions were interpreted from the dominant infilling processes, using standard sedimentary facies models for alluvial fans and fluvial deposition. These sedimentary facies were categorized into interpreted hydrogeologic facies, which were then compared with measured hydraulic conductivity data obtained from scattered aquifer pumping tests in the basin. The comparison suggests that sedimentary facies models can provide a good basis for estimating the distribution of relative hydraulic conductivity. Further, the comparison provides a procedure for estimating hydraulic conductivities in areas where no measured values are available. This procedure provides a better basis for estimating hydraulic conductivities than methods which do not consider sedimentary processes.