Scaling properties of saturated hydraulic conductivity in soil

Variability of saturated hydraulic conductivity, k(sat), increases when sam ple size decreases implying that saturated water flow might be a scaling pr ocess. The moments of scaling distributions observed at different resolutio ns can lie related by a power-law function, with the exponent being a singl e value (simple scaling) or a function (mutiscaling). Our objective was to investigate scaling characteristics of k(sat) using the method of the momen ts applied to measurements obtained with different sample sizes. We analyze d three data sets of k(sat) measured in: (I) cores with small diameter and increasing length spanning a single soil horizon, (2) columns with increasi ng cross sectional area and constant length, and (3) columns with increasin g cross sectional area and length, the longest column spanning three soil h orizons. Visible porosity (macroporosity) was traced on acetate transparenc y sheets prior to measurement of k(sat) in situation (2). Six moments were calculated assuming that observations followed normal (k(sat), macroporosit y) and/or log-normal (k(sat)) distributions. Scaling of k(sat) was observed in all three data sets. Simple scaling was only found when flux occurred i n small cross sectional areas of a simple soil horizon (data set (1)). Mult iscaling of k(sat) distributions was found when larger soil volumes were in volved in the flux process (data sets (2) and (3)). Moments of macroporosit y distributions showed multiscaling characteristics, with exponents similar to those from Ink(sat) distributions. The scaling characteristics of k(sat ) reported in this paper agree with similar results found at larger scales using semivariograms. Scaling exponents from the semivariogram and the mome nt techniques could be complemented, as demonstrated by the agreement betwe en macroporosity scaling exponents found with both techniques. (C) 1999 Els evier Science B.V. Ail rights reserved.