Hydrogeophysical approach to measure hydraulic parameters on unsaturated rocks

In the past decade, over-exploitation has led to a de-
pletion of water resources, with impact both on quality
and quantity. A sustainable groundwater management needs
a detailed scientific knowledge of the behaviour of the un-
saturated zone. Particularly, the evaluation of the flow-
rate in the unsaturated zone is important to estimate the
travel time of the infiltrated water in the subsurface and,
hence, to assess the recharge rate and groundwater vul-
nerability.
A quarry of calcarenite near the town of Canosa, in
South Italy, has been chosen to perform the field tests
using an integrated hydrogeophysical approach, combin-
ing infiltrometer measurements with electrical resistivity
tomography (ERT).
The infiltration data were collected using a metallic
infiltrometer ring of 0.5 m in diameter, installed directly
on the rock, filled with about 8 L of water. The test was
conducted for many hours at falling head condition, and
the water level within the ring was measured by means of
a pressure transductor and a metric rod fixed to the ring.
Simultaneously, electrical resistivity measurements
were carried out using "time-lapse" technique, in order to
monitor the dynamics of infiltration/redistribution of the
water in the unsaturated zone.
Hydrogeophysical data have been acquired for sev-
eral hours to obtain a reliable hydrogeological model of
the subsurface investigated.
Field-saturated hydraulic conductivity has been de-
termined for the calcarenite, and ERT surveys support
these results.