Abstracts

as mountainous terraines, and under different scales. This may be a reason why flownet
analysis is not used much in practice.
Flownets can be generated very easily by means of the dual theory of analysis. This
method, which comes from fluid dynamics, was first introduced in Canada in the
early 1980s by the first author, and it has since been enhanced by the second author.
The dual method consists of two governing equations: the standard equation for potentials,
and a complementary equation, based on the Cauchy-Riemann relationship,
for streamfunctions. The boundary conditions are also complementary. Because both
equations have the same form, they can be solved together using the same numerical
techniques. The plots of these two independent solutions give an accurate flownet
for any type of flow system, even under highly complex conditions or extreme scale
distortions. With some enhancements, it can also inform about groundwater age. The
only limitations are that flow is within the cross-sectional plane, of uniform density,
and at steady state, and the system has no internal sources or sinks. Incorporated into
the model FLONET, the dual solution can be used to verify 3D solutions for more
complex situations. A key feature is that the method can easily be used to test the
effect of many different configurations and boundary conditions for a given system –
giving answers to the ubiquitous “what if ” question – without running an expensive
3D model. Above all, it is a valuable teaching tool in both the classroom and the computer
lab, and as the above-mentioned former student aptly recognized, it gives a clear
understanding of how a groundwater system works.
311 - Unstated assumptions – a challenge for students and
hidden traps for the unwary
Garth van der Kamp
Water Science and Technology, Environment Canada, Saskatoon, Saskatchewan, Canada
In hydrogeology, as in all of human thought, there are always unstated assumptions.
Often it is precisely these invisible statements that turn out to cause the failure of the
bridge, or the unintended consequences of a government policy, or to be the critical
flaw in a paper in Water Resources Research. But it is also these assumptions that are
hardest to detect – they are smoothed over beautifully because usually the authors
are not even aware of them. Hydrogeology science and its publications contain many
examples of invalid unstated assumptions, as hidden traps for the unwary. Unstated
assumptions which are shared by a whole community of researchers are hardest to
detect – such paradigms are very interesting when they are identified, because that can
lead to major advances in the science!
We published a minor paper in Water Resources Research in 1969 (Carr and van der
Kamp, Vol. 5, 1023-1031) which contains a fatal flaw. The source of the error was an
unstated and invalid assumption in a 1950 publication by C.E. Jacob, a recognized
“authority” in hydrogeology, so we could be excused. It was three years later before
the error was identified by a graduate student (myself ) in an “aha!” moment while
puzzling over some strange observations that could not be explained by the theory in
192 IAH-CNC 2015 WATERLOO CONFERENCE