Soil Science Society of America Journal
TRANSIENT FLOW FROM TENSION INFILTROMETERS.
2. FOUR METHODS TO DETERMINE SORPTIVITY AND CONDUCTIVITY
Jean-Pierre Vandervaere1*, Michel Vauclin1 and Dave E. Elrick2
1
Laboratoire d'étude des Transferts en Hydrologie et Environnement
(CNRS UMR 5564, INPG, IRD, UJF) BP 53, 38041 Grenoble Cedex 9, France.
2
Department of Land Resource Science, University of Guelph
Guelph ON - N1G 2W1, Canada
ABSTRACT
In Part 1 of this series it was shown that the transient regime of axisymmetric
infiltration can be described by a two-term equation with one term proportional to the
square-root of time and the other term proportional to time. The two corresponding
coefficients, C1 and C2, are functions of the hydraulic conductivity, K, and the sorptivity,
S. In this paper, we propose four different methods to achieve the determination of S
and K. The four methods differ by the number of disk radii and the number of supply
pressure head values which are utilized. We show that the accuracy of a given method
is highly dependent on the combination of S and K values obtained. Three situations
can be distinguished, depending on the disk radius:
(i) the flow is dominated by the lateral capillary term;
(ii) the flow is dominated by the gravity term;
(iii) lateral capillary and gravity terms have equivalent weights.
The seven "model" soils tested here all correspond to the first situation with usual disk
radius values. This tends to show that a precise estimation of K is unlikely from disk
infiltrometer data. We introduce a new time scale, tStab, which generalizes the concepts
corresponding to the two well known time scales tgrav and tgeom. We propose a guideline
for the investigator to choose between all existing methods of analysis that use steady
or transient flow. Finally, the four new methods are tested against numerically
simulated tests with Grenoble sand and Yolo light clay.