Three-dimensional quantification of meltwater flow through a snowpack using a snow guillotine
In areas containing seasonal snowpacks, snowmelt contributes significantly to the hydrological cycle. Thus, quantifying the spatial distribution of flow through a snowpack is essential to accurate hydrograph interpretation and representation in snowmelt runoff modeling. Movement of liquid water through snowpacks is generally recognized to occur in distinct flow paths rather than as uniform flow through a homogeneous porous medium. Although dye tracer experiments have provided valuable qualitative information on meltwater flowpaths, quantitative descriptions of their spacing and location are not commonly available because of the difficulty in precisely excavating and measuring pathways. This makes it difficult to study scale and time-dependent processes such as the evolution of preferential flowpaths. Here we provide proof-of-concept using a new instrument we term ‘snow guillotine’ that provides quantitative information from dye tracer experiments in melting snowpacks. The structure of the snow guillotine allows the ability to take cross-sectional slices at 1-cm intervals of a snowpit where dye tracer has been applied. Photographs are taken of each cross-section over a one meter distance. Application of image processing and geostatistical analysis allows collection of high resolution (1cm3), three-dimensional data on meltwater flow through a snowpack.
Results illustrate preferential flowpaths, with the majority of vertical flow occurring in the upper 20-55cm of the snowpack, while fewer preferential flowpaths are apparent below 100cm. Layer interfaces were found to significantly increase the volume of dye, indicating dominance by lateral flow at these boundaries. These findings were supported by the decrease in probability with depth of finding vertical flow and an increase in the probability of finding lateral flow at layer interfaces. Preferential flowpaths decreased in distinctness with time after the snowpack reached isothermal conditions at 0oC. Implementation of the snow guillotine significantly improves field measurements of meltwater flow while providing three-dimensional, quantitative data of unprecedented spatial resolution.
