HR: 11:25h
AN: H21F-05    [PDF]
TI: Constraining Vadose Zone Models on Moisture Content Data Derived from Cross-Hole Radar
AU: Cassiani, G
EM: giorgio.cassiani@unimib.it
AF: Universit… di Milano-Bicocca, 1Dipartimento di Scienze Geologiche e Geotecnologie, Piazza della Scienza 4, Milano, 20125 Italy
AU: * Binley, A
EM: A.Binley@lancaster.ac.uk
AF: Lancaster University, Department of Environmental Science, Lancaster, LA1 4YQ United Kingdom
AB: The objective of this work is to analyze the value of cross-hole radar data in constraining unsaturated flow models, with the additional aims of estimating (a) the unsaturated flow parameters of the formations, and (b) the travel time of solutes from the ground surface to the water table. The specific application is a weakly consolidated sandstone (Sherwood Sandstone) in the UK, where vertical layering is the prevailing feature controlling the hydrological dynamics of the deep vadose zone. Zero-offset radar profiles were collected at the site for more than one year (Aug 1999 to Feb 2001). Data on site lithology come from core analysis and well logs. The principal tool applied in the analysis is numerical modeling in a stochastic (Monte Carlo) fashion. We generated conditional stochastic realizations of possible lithological sequences and random sets of unsaturated flow parameters for the materials considered, and compared simulated and radar-measured moisture content profiles. A few key aspects have been identified: (i) in order to compare measured and simulated moisture content data, it is essential to assess properly the scale of radar measurements, as governed by the antennae size, the Fresnel volume, and the refraction of radar energy into faster (dry) zones; (ii) the unsaturated flow parameters are not individually constrained by the quasi-stationary data at hand (equifinality); (c) the identification of flow parameters is, however, not necessary in order to derive a probabilistic estimate of travel time across the formation. The importance of acquiring independent information on the geology of the subsurface (here from well logs) cannot be overstressed.
DE: 0915 Downhole methods
DE: 1832 Groundwater transport
DE: 1866 Soil moisture
DE: 1875 Unsaturated zone
SC: Hydrology [H]
MN: 2003 Fall Meeting