HR: 16:25h
AN: H24A-02    [Abstracts]
TI: Rapid Hydrologic Responses due to Dynamic Contact Angles
AU: * Rasmussen, T C
EM: trasmuss@uga.edu
AF: Warnell School of Forest Resources, The University of Georgia, Athens, GA 30602-2152 United States
AB: Rapid hydrologic responses to rainfall are commonly attributed to macropore or preferential flow. Yet this explanation is inconsistent with many field experiments that indicate the presence of ``old'' water in stream inflows, along with matric tensions that are inconsistent with macropore saturation. Alternatively, rapid hydrologic responses can be explained using piston flow - even in unsaturated media. While this displacement effect is attenuated by saturation changes within the unsaturated zone, saturation changes are minimized when the air-soil-water meniscus line is immobile. The meniscus advance may be restricted by soil wettability, as well as by nanoscale surface roughness. Instead of a meniscus advance, the meniscus shape (e.g., the contact angle and capillary radius) may adjust to maintain a constant fluid potential. Dynamic contact angles substantially reduce saturation changes, which is consistent with observed slow tracer and rapid pressure responses in a large, saprolite column experiment.
UR: http://www.hydrology.uga.edu
DE: 1828 Groundwater hydraulics
DE: 1860 Streamflow
DE: 1875 Vadose zone
SC: Hydrology [H]
MN: Fall Meeting 2005