Frozen soil affects infiltration and subsurface flow, in a dynamic way, especially during early spring when soil temperature varies around the freezing point of water (0 °C). Under such conditions, soil hydraulic conductivity, influenced by both unfrozen water and ice contents, is temperature-dependent and varies both spatially and temporally. Particularly, the freeze-thaw cycle makes the flow system more complicated. The objective of this study is to develop an improved method to continuously simulate infiltration and soil water flow under both frozen and unfrozen conditions. Specifically, A modified Green-Ampt model is developed for simulating infiltration and unsaturated flow along a combined frozen and unfrozen heterogeneous soil profile of variable initial moisture distributions, as well as surface ponding and runoff processes under unsteady rainfall and/or snowmelt. The model was tested by using the data collected from a field site in Grand Forks, North Dakota. The observed data mainly included soil temperature and water content recorded by a set of soil moisture sensors installed at different depths (up to 100 cm). The simulations were compared against the observed data and the model performance was evaluated. This study demonstrated the applicability of the model for simulating infiltration and water flow in the frozen/unfrozen vadose zone, which potentially improves hydrologic modeling for cold climate regions.

Modeling of Infiltration and Unsaturated Flow under Cold Climate Conditions

Created in 1999, the Environmental & Water Resources Institute (EWRI) is the recognized leader within ASCE for the integration of technical expertise and public policy in the planning, design, construction, and operation of environmentally sound and sustainable infrastructure impacting air, land and water resources.