Abstract. Snowmelt is a major source of groundwater recharge in
cold regions. Throughout many landscapes snowmelt occurs when the ground is
still frozen; thus frozen soil processes play an important role in snowmelt
routing, and, by extension, the timing and magnitude of recharge. This study
investigated the vadose zone dynamics governing snowmelt infiltration and
groundwater recharge at three grassland sites in the Canadian Prairies over
the winter and spring of 2017. The region is characterized by numerous
topographic depressions where the ponding of snowmelt runoff results in focused
infiltration and recharge. Water balance estimates showed infiltration was
the dominant sink (35 %–85 %) of snowmelt under uplands (i.e. areas outside
of depressions), even when the ground was frozen, with soil moisture responses
indicating flow through the frozen layer. The refreezing of infiltrated
meltwater during winter melt events enhanced runoff generation in subsequent
melt events. At one site, time lags of up to 3 d between snow cover
depletion on uplands and ponding in depressions demonstrated the role of a
shallow subsurface transmission pathway or interflow through frozen soil in
routing snowmelt from uplands to depressions. At all sites,
depression-focused infiltration and recharge began before complete ground
thaw and a significant portion (45 %–100 %) occurred while the ground was
partially frozen. Relatively rapid infiltration rates and non-sequential
soil moisture and groundwater responses, observed prior to ground thaw,
indicated preferential flow through frozen soils. The preferential flow
dynamics are attributed to macropore networks within the grassland soils,
which allow infiltrated meltwater to bypass portions of the frozen soil
matrix and facilitate both the lateral transport of meltwater between
topographic positions and groundwater recharge through frozen ground. Both
of these flow paths may facilitate preferential mass transport to
groundwater.
Thermal impact of buried reservoirs with industrial waste of the fuel and energy complex on frozen soils
