Liquid water infiltration into a layered snowpack: evaluation of a 3-D water transport model with laboratory experiments

Hiroyuki Hirashima,Francesco Avanzi,Satoru Yamaguchi

doi:10.5194/hess-21-5503-2017

Abstract

Abstract. The heterogeneous movement of liquid water through the snowpack during precipitation and snowmelt leads to complex liquid water distributions that are important for avalanche and runoff forecasting. We reproduced the formation of capillary barriers and the development of preferential flow through snow using a three-dimensional water transport model, which was then validated using laboratory experiments of liquid water infiltration into layered, initially dry snow. Three-dimensional simulations assumed the same column shape and size, grain size, snow density, and water input rate as the laboratory experiments. Model evaluation focused on the timing of water movement, thickness of the upper layer affected by ponding, water content profiles and wet snow fraction. Simulation results showed that the model reconstructs relevant features of capillary barriers, including ponding in the upper layer, preferential infiltration far from the interface, and the timing of liquid water arrival at the snow base. In contrast, the area of preferential flow paths was usually underestimated and consequently the averaged water content in areas characterized by preferential flow paths was also underestimated. Improving the representation of preferential infiltration into initially dry snow is necessary to reproduce the transition from a dry-snow-dominant condition to a wet-snow-dominant one, especially in long-period simulations.

Highlights

The heterogeneous movement of liquid water through the snowpack during precipitation and snowmelt leads to complex liquid water distributions that impact the snow structure through wet snow metamorphism
The results showed that for the fine-over-coarse snow (FC) and fine-over-medium snow (FM) experiments, the liquid water content was overestimated near the interfaces between snow layers in the upper fine layer but underestimated in other areas
While Avanzi et al (2016) compared their results with SNOWPACK-3.3.0 simulations at the end of each experiment, a direct comparison between models can be made for any point of time

Summary

Introduction

The heterogeneous movement of liquid water through the snowpack during precipitation and snowmelt leads to complex liquid water distributions that impact the snow structure through wet snow metamorphism. In the early theories of liquid water movement, capillary gradients in snow were usually neglected (Colbeck, 1972; Colbeck and Davidson, 1972; Colbeck, 1974a, b, 1976; Dunne et al, 1976; Wankiewicz, 1978). A 2-D model by Daanen and Nieber (2009) adopted a van Genuchten model with dependence on grain size. For each of these models, the main cause of heterogeneous water movement was attributed to refreezing and ice layers.

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Conclusion