UC Santa Barbara

This paper reviews the role of probability density function (PDF) choice on: (1) the statistical characterization of hydraulic conductivity; and (2) the estimation of the local-scale effective hydraulic conductivity. The most widely used skewed PDFs, namely, the lognormal, gamma, and log-gamma PDFs are included in this study. It is shown that the gamma and log-gamma PDFs possess statistical features that render them competitive, if not advantageous, to the more commonly used and better-known lognormal PDF in: (1) the statistical description of hydraulic conductivity; and (2) the estimation of the effective hydraulic conductivity in local-scale groundwater flow. The effective hydraulic conductivity is the parameter relating the average specific discharge to the average hydraulic gradient. Several examples dealing with the statistical analysis of hydraulic conductivity and the estimation of the effective hydraulic conductivity are presented, including a sample of 201 slug-test measurements of hydraulic conductivity in the main clay aquitard underlying Mexico City. © 2006 ASCE.