EGU General Assembly location:Vienna date:22-27 April 2012
Saturated hydraulic conductivity (Ks) is one of the most important parameters determining groundwater ﬂow and
contaminant transport in both unsaturated and saturated porous media. Determining the small-scale variability of
this parameter is key to evaluate implications on effective parameters at the larger scale. Moreover, for stochastic
simulations of groundwater ﬂow and contaminant transport, accurate models on the spatial variability of Ks are
very much needed. While several well-established laboratory methods exist for determining Ks, investigating the
small-scale variability remains a challenge. If several tens to hundreds of metres of borehole core has to be hy-
draulically characterised at the centimetre to decimetre scale, several hundreds to thousands of Ks measurements
are required, which makes it very costly and time-consuming should traditional methods be used.
With reliable air permeameters becoming increasingly available from the late 80’s, a fast and effective indirect
method exists to determine Ks. Therefore, the use of hand-held air permeameter measurements for determining
very accurate small-scale heterogeneity about Ks is very appealing. Very little is known, however, on its applica-
bility for borehole cores that typically carry a small sediment volume. Therefore, the method was tested on several
borehole cores of different size, originating from the Campine basin, Northern Belgium. The studied sediments are
of Miocene to Pleistocene age, with a marine to continental origin, and consist of sand to clayey sand with distinct
clay lenses, resulting in a Ks range of 7 orders of magnitude. During previous studies, two samples were taken
from borehole cores each two meters for performing constant head lab permeameter tests. This data is now used
as a reference for the air permeameter measurements that are performed with a resolution of 5 centimetres.
Preliminary results indicate a very good correlation between the previously gathered constant head Ks data and the
air permeability measurements, but a systematic bias seems to exist. A geostatistical analysis with cross-validation
is performed to assess the predictive uncertainty on Ks, using both types of data.
We conclude that performing hand-held air permeameter measurements on undisturbed borehole cores provides a
very cost-effective way to obtain very detailed information in the framework of stochastic simulation and condi-
tioning of heterogeneous hydraulic conductivity ﬁelds.