ON THE REALTIVE IMPORTANCE OF LATERAL FLOW IN SOIL AND SNOW

A snowpack is a porous media that can store and transmits water. While similar to soil water flow, flow in snow exhibits some unusual and interesting behavior. For example, the source of the medium can be the media itself. In sloping terrain, melting snow or rain can generate significant amounts of downslope water movement., yet the hydrologic significance of lateral flow in soil has rarely been addressed. In this study, we used dye tracers, geophysical methods, and hydrometric measurements to compare the rates and volumes of lateral flow in snow versus soil during the snowmelt period in a mid-elevation mountain catchment near Boise, Idaho. Results demonstrate that rain and melt water can travel tens of meters downslope within hours. Later flow within the snowpack becomes less likely as the snowpack becomes saturated and stratigraphy is destroyed. Flow along the base can be prevalent in all snowpack conditions. The net result of lateral flow in snow can be deposition of water on the tsoil surface in advanced downslope positions relative to its point of origin, or direct discharge to a stream. In catchments with a persistent snowpack, lateral redistribution of water within the snowpack can be as important as flow in soil in some conditions.