HR: 0800h
AN: H21E-1389    [Abstracts]
TI: Effects of use of sloping boreholes on vadose zone monitoring
AU: * Hinnell, A C
EM: andrew@hwr.arizona.edu
AF: University of Arizona Department of Hydrology and Water Resources, 1133 E North Campus Dr., Tucson, AZ 85721-0011 United States
AU: Ferre, T P
EM: ty@hwr.arizona.edu
AF: University of Arizona Department of Hydrology and Water Resources, 1133 E North Campus Dr., Tucson, AZ 85721-0011 United States
AU: Warrick, A W
EM: aww@ag.arizona.edu
AF: University of Arizona Department of Soil Water and Environmental Science, P.O. Box 210038, Tucson, AZ 85721-0038 United States
AB: Phillips (1989) introduced an analytical solution for the pressure distribution in the plane perpendicular to a sloping, infinite borehole in an unsaturated medium experiencing steady-state unit-gradient flow. We develop a numerical model to examine deviations from this solution for three-dimensional non-infinite media (e.g. proximal boundaries such as the ground surface). From our solution we develop guidelines for conditions that are amenable to the Phillips solution. Then, we relate the water content distribution to the pressure head distribution. Based on these results, we discuss the spatial distribution of water content in the plane perpendicular to a sloping borehole. We show that, for measurement methods with small sample areas (e.g. TDR), there are optimal angular locations around the borehole to recover the undisturbed water content. We also show that measurement methods with intermediate sample volumes (e.g. neutron probes) may be impacted by flow disruption caused by the sloping borehole. The optimal angular location for point methods and the degree of error for non-point methods vary with the medium properties, the applied flux, and the borehole design.
DE: 1829 Groundwater hydrology
DE: 1835 Hydrogeophysics
DE: 1866 Soil moisture
DE: 1875 Vadose zone
SC: Hydrology [H]
MN: Fall Meeting 2005