Improved characterization through joint hydrogeophysical inversion: Examples of three different approaches Page: 1 of 2
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Improved characterization rough joint hydrogeophysical inversion:
Examples of three diferent approaches
Niklas Lindel ,3, Jinsong Chen1, Michael Kowalskyl, Stefan Finsterlel, Yoram
Rubin2 and Susan Hubbard1
1Earth Science Division, Lawrence Berkeley National Laboratory, MS 90-1116, 1
Cyclotron Rd., Berkeley, CA 94720, USA.
2Department of Civil and Environmental Engineering, University of California,
Berkeley, CA 94720, USA.
3Department of Earth Sciences/Geophysics, Uppsala University, Villav. 16, 752 36
Uppsala, Sweden.
With the increasing application of geophysical methods to hydrogeological problems,
approaches for obtaining quantitative estimates of hydrogeological parameters using
geophysical data are in great demand. A common approach to hydrogeological parameter
estimation using geophysical and hydrogeological data is to first invert the geophysical
data using a geophysical inversion procedure, and subsequently use the resulting
estimates together with available hydrogeological information to estimate a
hydrogeological parameter field. This approach does not allow us to constrain the
geophysical inversion by hydrogeological data and prior information, and thus decreases
our ability to make valid estimates of the hydrogeological parameter field. Furthermore, it
is difficult to quantify the uncertainty in the corresponding estimates and to validate the
assumptions made. We are developing alternative approaches that allow for the joint
inversion of all available hydrological and geophysical data. In this presentation, we
consider three studies and draw various conclusions, such as on the potential benefits of
estimating the petrophysical relationships within the inversion framework and of
constraining our geophysical estimates on geophysical, as well as hydrogeological data.
In the first approach, we use information obtained from radar tomographic velocity
zones to invert tracer test data. We invert the hydrogeological field using non-stationary,
unknown empirical petrophysical relationships and only use the information in the
tomogram that helps us to fit the tracer test data. Synthetic studies are used to assess the
effects of non-random errors in the intrinsic petrophysical relationships, and how
geophysical data acquisition errors (e.g., unknown borehole deviations, unknown zero-
times) affect our estimates. We conclude that we can estimate the spatial variability of the
hydrogeological field given a strong intrinsic petrophysical relationships (p>0.8) and
very carefully collected geophysical data. The results also illustrate the limitations of a
sequential deterministic inversion approach.
In the second approach, crosshole ground-penetrating radar (GPR) travel times and
hydrological measurements, collected before and during transient flow experiments, are
used jointly to estimate flow parameter distributions in the vadose zone (and their
uncertainty). This approach employs concepts from the Pilot Point method in a maximum
a posteriori framework and requires the joint simulation of variably saturated flow and
GPR travel times. In a synthetic 2D example, the permeability distribution is estimated,
and additional parameters of the relative permeability and capillary pressure functions are
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Linde, Niklas; Chen, Jinsong; Kowalsky, Michael; Finsterle,Stefan; Rubin, Yoram & Hubbard, Susan. Improved characterization through joint hydrogeophysical inversion: Examples of three different approaches, article, July 1, 2004; Berkeley, California. (https://digital.library.unt.edu/ark:/67531/metadc887127/m1/1/: accessed March 18, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.