Two-Dimensional Liquid Water Flow through Snow at the Plot Scalein Continental Snowpacks: Simulations and Field Data Comparisons

Abstract. Modelling the multi-dimensional flow of liquid water through snow has been limited in spatial and temporal scales to date. Here we present simulations using the iTOUGH2 model informed by the model SNOWPACK, referred to as SnowTOUGH. We use SnowTOUGH to simulate snow metamorphism, melt/freeze processes, and liquid water movement in two-dimensional snowpacks at the plot scale (20 m) on a sloping ground surface during multi-day observation periods at three field sites in northern Colorado, USA. Model results compare well with subalpine and alpine sites, but not a treeline site. Results show the importance of longitudinal (i.e. parallel to ground surface in the downslope direction) intra-snowpack flow paths, particularly during times when the snow surface (i.e. snow-atmosphere interface) is not actively melting. Simulations show that longitudinal flow can occur at rates orders of magnitude greater than vertically downward percolating water flow (a ratio of > 250 : 1) as a result of hydraulic barriers.