Preferential transport of water and 131Iodide in a clay loam assessed with TDR-techniques and boundary-layer flow theory
Other literature type
Mdaghri Alaoui, A.
(issn: 1607-7938, eissn: 1607-7938)
Rapid soil moisture variations were measured with TDR
equipment at five depths ranging from 0.1 to 0.9 m during five consecutive infiltration experiments under
ponding. Each time, 27 mm of water were applied. The water of the second experiment was spiked
with 200 mbq of K<sup>131</sup>I-tracer. Its activity was recorded as functions of depth and time
with Geiger-Müller probes in 12 vertically installed access tubes. The soil moisture variations
were classified as showing (i) no reaction, (ii) monotonous increase, and (iii) rapid increase followed
by a gradual decrease. Reaction type (iii) was investigated further according to the boundary-layer
flow theory and diagnosed as preferential flow. Rapid variations of <sup>131</sup>I-activities
occurred at all depths showing soil moisture reaction type (iii). However, some of the reaction
types (i) and (ii) also included rapid variations of the activities.
<br>The approach based on boundary-laver flow theory
allows fluxes to be estimated from soil moisture variations. Seven estimated total volumes of rapid flow ranged
from 0.15 to 1.1 of the applied volume of water, and in only one case was the total volume
badly overestimated by a factor of almost 3. The approach is worth further exploration.