Negative correlation between porosity and hydraulic conductivity in sand-and-gravel aquifers at Cape Cod, Massachusetts, USA

Authors

• Roger H. Morin, Denver Federal CenterFollow

Document Type

Article

Date of this Version

2005

Comments

Published in Journal of Hydrology 316 (2006) 43–52

Abstract

Although it may be intuitive to think of the hydraulic conductivity K of unconsolidated, coarse-grained sediments as increasing monotonically with increasing porosity ɸ , studies have documented a negative correlation between these two parameters under certain grain-size distributions and packing arrangements. This is confirmed at two sites on Cape Cod, Massachusetts, USA, where groundwater investigations were conducted in sand-and-gravel aquifers specifically to examine the interdependency of several aquifer properties using measurements from four geophysical well logs. Along with K and ɸ , the electrical resistivity R₀ and the natural gamma activity γ of saturated deposits were determined as functions of depth. Qualitative examination of results from the first site implies a negative correlation between K and ɸ that is substantiated by a rigorous multivariate analysis of log data collected from the second site. A principal components analysis describes an over determined system of inversion equations, with approximately 92% of the cumulative proportion of the total variance being accounted for by only three of the four eigenvectors. A subsequent R-mode factor analysis projects directional trends among the four variables (K, ɸ , R₀ and γ), and a negative correlation between K and ɸ emerges as the primary result. q 2005 Elsevier B.V. All rights reserved.