Hydrogeophysics 2012 Workshop
HOMEWORK SESSIONS
1) The Use of Electrical Resistivity Measurements for
Monitoring Subsurface Processes: Quantifying Noise and Uncertainty
The focus of the homework in this session is the characterization
of data noise and the uncertainty associated with the inversion of electrical
resistivity data. The data set provided
includes two lines of Wenner measurements made with
electrodes in the base of a recharge pond. The measurements recorded changes in
the subsurface conductivity structure during and after a rainfall event prior
to filling of the recharge pond; it captures periods of both increasing and
decreasing water saturation. The
homework: Invert the data, then characterize the
measurement noise and/or the uncertainty of the inverted image.
2) The Ultimate Tomography Bake-Off Challenge Using Boise
Hydrogeophysical Research Site Borehole Seismic and
GPR Datasets
It is rare that many different investigators independently analyze
a single dataset and then compare results to gain insight into uncertainty in
solutions, differences in processing algorithms, or variations in petrophysical assumptions.
Rarer still are instances when such an effort has been undertaken with
field data. This session will focus on borehole-to-borehole, and borehole-to-surface tomographic
inversion and will take advantage of the unique control database afforded by
the Boise Hydrogeophysical Research Site. We have acquired a coincident seismic and GPR
borehole-to-borehole, and borehole-to-surface dataset with a similar geometry
and source characteristics selected to produce a similar wavelength in the
saturated zone. The data will be
available for download from the CGISS web page on November 15, 2011. Participants in this session are invited to
download all or any subset of the data and use any preferred method for
inversion. The objective will be to
produce compressional and/or electromagnetic wave velocity tomograms and
porosity distributions.
"Control" data will consist of the results of previously
analyzed VSP, VRP, and neutron-neutron probe surveys acquired in the two acquisition
boreholes and in a coincident interior borehole. Participant's results will be compared with
each other and with the "control" data. The objective of the session
is not to determine the "right" answer but rather to better
understand differences in analysis methods.
3) "Designing the
Perfect Field Experiment" Homework Session
In this homework session, participants are to design a
set of field experiments to predict, as accurately as possible and within a
framework of uncertainty, the transport of an electrically conductive contaminant
in a realistic, highly heterogeneous, synthetic subsurface aquifer. The aquifer
model, which is 80 m long by 50 m wide by 35 m deep and defined at a resolution
of 0.25 m, represents a glaciofluvial environment
consisting largely of sands and gravels and is based on an upscaled
version of the recently published Herten 3-D dataset (Bayer et al., 2011; Comunian et al., 2011; Figure 1). The accompanying MATLAB
file workshop_data.mat contains the 3-D aquifer facies distribution and some of its hydrogeological and
geophysical properties. Details regarding this file, the corresponding hydrological
boundary conditions, and the contaminant transport problem to be considered are
provided below.