A geophysical and geochemical study has been conducted in a fractured
carbonate aquifer located at Combioula in the southwestern Swiss
Alps with the objective to detect and characterize hydraulically
active fractures along a 260-m-deep borehole. Hydrochemical analyses,
borehole diameter, temperature and fluid electrical conductivity
logging data were integrated in order to relate electrokinetic self-potential
signals to groundwater flow inside the fracture network. The results
show a generally good, albeit locally variable correlation of variations
of the self-potential signals with variations in temperature, fluid
electrical conductivity and borehole diameter. Together with the
hydrochemical evidence, which was found to be critical for the interpretation
of the self-potential data, these measurements not only made it possible
to detect the hydraulically active fractures but also to characterize
them as zones of fluid gain or fluid loss. The results complement
the available information from the corresponding litholog and illustrate
the potential of electrokinetic self-potential signals in conjunction
with temperature, fluid electrical conductivity and hydrochemical
analyses for the characterization of fractured aquifers, and thus
may offer a perspective for an effective quantitative characterization
of this increasingly important class of aquifers and geothermal reservoirs.