Resistivity and percolation study of preferential flow in vadose zone at Bokhorst, Germany

Traditional nondestructive resistivity techniques have been applied in combination with tracer displacement and conventional soil moisture recording methods [i.e., buried tensiometer and time domain reflectometry (TDR)] for studying flow processes at an arable site in Bokhorst, Germany. Three water infiltration experiments were carried out using tap water spiked with a nonreactive tracer at different concentrations. The study aimed at exploring the capabilities of these combined techniques for tracing the preferential movement of water in the uppermost 1.5 m of the highly heterogeneous vadose zone. The results illustrate that the applied tensiometer and TDR techniques can detect the relatively fast flow process at their position points and thus only tentatively trace the preferential flow. The additional application of the resistivity method can trace the preferential flow paths continuously along the plane of measurements. The results of the individual applied methods complement and confirm each other.