Soil water distribution as observed by methods of geophysics

摘要

We are studying three-dimensional soil moisture patterns in the unsaturated zone using non-invasive geophysical techniques. In a full-scale sand tank, infiltration experiments with a constant irrigation rate indicate a water front moving uniformly downwards through homogeneous sand. Under natural conditions, first results in a peach orchard in Portugal show the morphology of preferential flow paths in the root zone of trees and its heterogeneous sand surroundings. For drop irrigation, the wetting ofthe root zone and the inhomogeneous flow paths can be clearly observed. This wetting is faster and more effective with daily irrigation than after one week of dryness. Strong preferential flow paths are observed under infiltration by using a dye tracer. The flow situation in this experiment is close to natural ponding.