HR: 1340h
AN: H23E-1465    [Abstracts]
TI: A Hydraulic Tomographic Approach: Coupling of Travel Time and Amplitude Inversion Using Multivariate Statistics
AU: * Brauchler, R
EM: rbrauch@gwdg.de
AF: Geoscience Center of the University of Goettingen, Goldschmidtstrasse 3, Goettingen, 37077 Germany
AU: Cheng, J
H23E-1465 AF: University of California, Irvine Civil and Environmental Engineering, Irvine, CA 92697-2175, Irvine, CA 92697 United States
AU: Dietrich, P
H23E-1465 AF: Center for Applied Geoscience, University of Tuebingen, Sigwartstrasse 10, Tuebingen, 72067 Germany
AU: Everett, M
H23E-1465 AF: Department of Geology and Geophysics, Texas A&M University, College Station, TX 77843-3115, College Station, TX 77843 United States
AU: Johnson, B
H23E-1465 AF: Department of Geology and Geophysics, Texas A&M University, College Station, TX 77843-3115, College Station, TX 77843 United States
AU: Sauter, M
H23E-1465 AF: Geoscience Center of the University of Goettingen, Goldschmidtstrasse 3, Goettingen, 37077 Germany
AB: Knowledge about the spatial variations in hydraulic properties plays an important role controlling solute movement in saturated flow systems. Traditional hydrogeological approaches appear to have difficulties providing high resolution parameter estimates. Thus, we have decided to develop an approach coupling the two existing hydraulic tomographic approaches: a) Inversion of the drawdown as a function of time (amplitude inversion) and b) the inversion of travel times of the pressure disturbance. The advantages of hydraulic travel time tomography are its high structural resolution and computational efficiency. However, travel times are primarily controlled by the aquifer diffusivity making it difficult to determine hydraulically conductivity and storage. Amplitude inversion on the other hand is able to determine hydraulic conductivity and storage separately, but the heavy computational burden of the amplitude inversion is often a shortcoming, especially for larger data sets. Our coupled inversion approach was developed and tested using synthetic data sets. The data base of the inversion comprises simulated slug tests, in which the position of the sources (injection ports) isolated with packers, are varied between the tests. The first step was the inversion of several characteristic travel times (e.g. early, intermediate and late travel times) in order to determine the diffusivity distribution. Secondly, the resulting diffusivity distributions were classified into homogeneous groups in order to differentiate between hydrogeological units characterized by a significant diffusivity contrast. The classification was performed by using multivariate statistics. With a numerical flow model and an automatic parameter estimator the amplitude inversion was performed in a final step. The classified diffusivity distribution is an excellent starting model for the amplitude inversion and allows to reduce strongly the calculation time. The final amplitude inversion overcomes efficiently the limitation of travel time inversion and allows to determine hydraulic conductivity and storage at high resolution.
DE: 1828 Groundwater hydraulics
DE: 1829 Groundwater hydrology
DE: 1835 Hydrogeophysics
SC: Hydrology [H]
MN: Fall Meeting 2005