Simple predictions of maximum transport rate in unsaturated soil and rock

Water Resources Research



In contrast with the extreme variability expected for water and contaminant fluxes in the unsaturated zone, evidence from 64 field tests of preferential flow indicates that the maximum transport speed Vmax, adjusted for episodicity of infiltration, deviates little from a geometric mean of 13 m/d. A model based on constant‐speed travel during infiltration pulses of actual or estimated duration can predict Vmax with approximate order‐of‐magnitude accuracy, irrespective of medium or travel distance, thereby facilitating such problems as the prediction of worst‐case contaminant traveltimes. The lesser variability suggests that preferential flow is subject to rate‐limiting mechanisms analogous to those that impose a terminal velocity on objects in free fall and to rate‐compensating mechanisms analogous to Le Chatlier's principle. A critical feature allowing such mechanisms to dominate may be the presence of interfacial boundaries confined by neither solid material nor capillary forces.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Simple predictions of maximum transport rate in unsaturated soil and rock
Series title Water Resources Research
DOI 10.1029/2006WR005372
Volume 43
Issue 5
Year Published 2007
Language English
Publisher American Geophysical Union
Contributing office(s) Toxic Substances Hydrology Program
Description W05426; 11 p.
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