Publication Details

Category Text Publication
Reference Category Journals
DOI 10.2136/vzj2011.0134
Title (Primary) Conductivity and hydraulic nonequilibrium across drainage and infiltration fronts
Author Weller, U.; Vogel, H.-J.
Journal Vadose Zone Journal
Year 2012
Department BOPHY
Volume 11
Issue 3
Page From 10.2136/vzj2011.0134
Language englisch

We present a new and rather simple technique for the direct measurement of unsaturated hydraulic conductivity in soils. In addition, our approach reveals the dynamics of hydraulic nonequilibrium during transient conditions and the hysteresis of the process.

Recently, a new approach was introduced to directly measure unsaturated hydraulic conductivity in flux-controlled experiments—the multistep flux experiment. Thereby an overshoot in matric potential hm across drainage and infiltration fronts was observed. We extended this experimental approach to simultaneously measure the volumetric water content θ within the sample and applied the method to a sand and a clay loam soil. The detailed trajectories within the hm–θ space were obtained during a number of decreasing and increasing steps in infiltration rate. This clearly demonstrates the type and magnitude of hydraulic nonequilibrium under transient conditions where water content and matric potential deviate from a well-defined static relation. We also compared the directly measured hydraulic conductivities with those obtained from classical multistep outflow experiments and found that nonequilibrium dynamics might lead to an underestimation of hydraulic conductivity when obtained from an inverse solution of Richards’ equation. We provide a qualitative explanation of nonequilibrium that depends on the structure of the material and the type and magnitude of external forcing. The new experimental setup is considered to be a valuable tool to actually quantify nonequilibrium effects. This will make it possible to represent this relevant phenomenon in future modeling concepts.

Persistent UFZ Identifier
Weller, U., Vogel, H.-J. (2012):
Conductivity and hydraulic nonequilibrium across drainage and infiltration fronts
Vadose Zone J. 11 (3), 10.2136/vzj2011.0134