HR: 0800h
AN: H31F-1361    [Abstracts]
TI: Air Entrapment, Soil Water Retention and Distributed Hydrologic Response in a Semi Arid Catchment
AU: * Cahndler, D G
EM: david.chandler@usu.edu
AF: Department of Plants, Soils and Biometeorology Utah State University, 4820 Old Main Hill, Logan, UT 84322-4820 United States
AU: McNamara, J P
EM: jmcnamar@boisestate.edu
AF: Department of Geosciences Boise State University, 1910 University Drive, Boise, ID 83725 United States
AU: Gribb, M M
EM: mgribb@boisestate.edu
AF: Department of Civil and Environmental Engineering Boise State University, 1910 University Dr., Boise, ID 83725 United States
AB: Numerical hydrologic models are beginning to incorporate more sophisticated representations of soil physical properties. A remaining obstacle in the implementation of this approach is that the hydraulic properties of soil do not scale well, limiting the application of pedotransfer functions. To address this knowledge gap, the relationships among soil water inputs, distributed soil state variables and streamflow were investigated for a zero order catchment in a semi-arid system. Soil water potential and soil moisture content measurements for several locations along hillslope transects were made over a hydrologic year. In addition, pedotransfer functions were developed from spatially distributed soil cores at the surface and from various depths. These data are used to support hypotheses of the spatial variability in hydrologic flowpaths in this system and the relationships among soil water retention curves, vertical and lateral hydraulic connectivity in this system. Specifically, we propose the hypothesis that air entrapment is typical for this system and has a dramatic influence on the delivery of snowmelt and rain to streamflow. Phenomenological evidence includes observations of pipe flow near the surface during snowmelt, in the absence of any measured soil saturation above the base of the soil column. Secondly, we propose the hypothesis that hillslope sensor locations demonstrate hydraulic connection to the stream through wetting and drainage timing synchronous with the rising and falling limbs of the hydrograph. These two hypotheses support the concept of hydrograph generation above base flow driven by a pressure wave from hydraulically connected locations, which may vary with volume of entrapped air, but is largely controlled by the distribution of water inputs, soil depth and extent of the macropore drainage network. Testing the posed hypotheses of hydrologic process in the context of pedotransfer functions will allow advances in field hydrology to inform modeling efforts.
DE: 1804 Catchment
DE: 1838 Infiltration
DE: 1860 Streamflow
DE: 1865 Soils (0486)
DE: 1875 Vadose zone
SC: Hydrology [H]
MN: Fall Meeting 2005