Over winter freeze-thaw events are notoriously difficult to represent in
hydrologic models and have serious implications for the hydrologic
function of intermittently freezing regions. With changing climate
leading to higher variability in observed weather patterns, it is
anticipated that mid-winter thaw events may become more numerous at
locales where intermittent thaw was previously rare. Midwinter thaw
events are often the cause of flooding due to the combined impacts of
snowmelt, precipitation, and limited soil infiltrability. A numerically
efficient, semi-analytical coupled thermal and mass transport model is
presented that is capable of representing the ice content of
near-surface soil. This model allows for rapid and stable prediction of
the ice content of frozen or partially frozen near-surface soil without
having to solve a discrete form of the coupled partial differential
equations describing the soil water and energy balance. The model tracks
pore ice formation and mean soil temperature in terms of enthalpy. It is
tested against data collected in Southern Saskatchewan and is shown to
capably reproduce field observations. This model is efficient enough to
be incorporated as a module into existing regional hydrologic models and
is expected to improve predictions of soil ice content, which can later
lead to improved estimates of over-winter streamflow and flood
potential.