The prairie pothole is an important hydrologic component of the Prairie Pot
hole Region of North America. Snow cover and frozen soil affect runoff and
soil water recharge, but little is known about their temporal and spatial c
haracteristics across a prairie pothole. A 2-ha prairie pothole near Morris
, MN was instrumented to assess snow cover, soil water, and frost depth at
11 locations across two transects that traversed the major and minor axes.
Measurements were made over three winters beginning in 1990, Snow cover was
deepest on the leeward side of a ridge located on the NW end of the major
axis and shallowest and least variable in the bottom of the depression. Max
imum rate of descent of the freezing front in the soil approached 25 mm d(-
1) whereas maximum depth of soil freezing neared 1.2 m across the experimen
tal site during this study. Rate of soil freezing during the fall was more
rapid at positions of higher elevation and with thinner snow cover. Elevati
on and snow cover accounted for as much as 56% of the variability in rate o
f soil freezing across the site. Snow cover accounted for as much as 46% of
the variation in maximum frost penetration; penetration was deepest at pos
itions with the least snow cover. Thawing of the soil profile was most rapi
d in the bottom of the depression and appeared to be accentuated by infiltr
ation of surface water through localized unfrozen soil pores or cracks, Max
imum surface thaw rate approached 40 mm d(-1). Soil water recharge occurred
during spring snowmelt, but snow cover accounted for <20% of the variation
in recharge. This study suggests that topographic features across a prairi
e pothole can influence snow cover and, therefore, frost depth. Thickness o
f snow cover, however, has little influence on positional soil water rechar
ge within a pothole during snowmelt because frozen soil can impede infiltra
tion and enhance runoff.