Macropore Flow in Frozen Soils

Snowmelt is the major source of freshwater in many cold regions. The ground is usually frozen when snowmelt begins, and consequently, the permeability of frozen ground has a significant influence on a watershed’s response to snowmelt. Although frozen ground is sometimes thought to function as an impermeable barrier that inhibits downward flow, preferential flow of water through larger pores may bypass the frozen soil matrix. This phenomenon has been studied for several decades, but progress has been hindered by the lack of a clear conceptualization of the dominant flow mechanisms and how they vary in response to different soil thermal regimes. This has historically limited the development and application of models that consider the interacting effects of soil freeze-thaw and preferential flow.