Item: Measurement of dynamic waterentry value for dry snow
Title: Measurement of dynamic waterentry value for dry snow
Proceedings: International Snow Science Workshop, Davos 2009, Proceedings
Authors: Takafumi Katsushima, Satoru Yamaguchi, Toshiro Kumakura and Atsushi Sato, Nagaoka University of Technology, Nagaokacity, Niigata, JAPAN 2Snow and Ice Research Center, National Research Institute for Earth Science and Disaster Prevention, Nagaok
Abstract: In soil physics, many people have discussed about mechanisms of developing preferential flow based on porous media hydraulics. In snow science, there are few studies on the preferential flow though the preferential flow governs a part of runoff process in a snowpack. Dry sand has a waterentry value which is a threshold value of the capillary pressure to start infiltration into dry sand. Water cannot infiltrate in the situation that the capillary pressure at the wetting front is less than the waterentry value. The preferential flow is developed in the upwardnegative gradient of the capillary pressure behind the wetting front, which is appeared in the case that the waterentry value is larger than the capillary pressure along the upper moving path of the wetting front. It is thought that the phenomena on the preferential flow in the sand are almost same as these in the snow and the waterentry value of the homogeneous dry snow layer is important to study the preferential flow in the snowpack. In this study, the waterentry values were obtained by measuring the capillary pressure at the wetting front penetrating into the underlying dry snow. The capillary pressure was measured with the high response tensiometers. The measured waterentry values were greater than the airentry value according to the water retention curve for drying process. The waterentry value with large diameter is larger than one with small. The some paths of the preferential flow were observed in these experiments. On the other hand, the waterentry value was not observed and the preferential flow was not observed in the experiment which used the smaller diameters of snow particles.
Keywords: preferential flow, waterentry value, homogeneous dry snow
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