Formation and persistence of fingered flow fields in coarse grained soils under different moisture contents
1994
Liu, Y. | Steenhuis, T.S. | Parlange, J.Y.
Fingers in homogeneous coarse-grained soils form from an instability in the wetting front and result in bypass flow which shortens the residence time in the vadose zone. Once formed, these fingers persist over a long period. In this paper, the formation of fingers and their persistence in initially uniform dry or wet soils are examined. Using fast-responding tensiometers in conjunction with rapid moisture measurements, it is shown that the matric potential at the finger tip and the position of the wetting curve relative to the drying curve are key factors in the persistence of the fingers. In accordance with the earlier observation, the tip and the fringes of the finger are on a wetting curve, while the remaining core of the finger is on a drying branch. This explains why large differences in moisture content can co-exist. This study also shows that the initial water content in and around the finger is crucially important in relation to which particular scanning curve is followed and, thus, to the water contents during infiltration.
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