Hydraulic Characterization of the Vadose Zone of Calcareous Rock using Infiltrometer and Electrical Resistivity Tomography Measurements.

Sustainable groundwater management requires a thorough knowledge of the behavior of the unsaturated zone. Particularly, the evaluation of the flow rate in the unsaturated zone is important to estimate the travel time of the infiltrated water and dissolved substances in the subsurface and, hence, to quantify the recharge rate and to assess the quality of the subsurface. A quarry of calcarenite near the town of Canosa, in southern Italy, was chosen to perform an integrated hydrogeophysical field study that combines infiltrometer measurements with Electrical Resistivity Tomography (ERT). Infiltration data were collected using a 0.5-m-diameter metallic infiltrometer ring, which was installed directly on the rock, filled with about 8 L of water. A falling-head test was conducted for many hours, the water level in the ring was monitored with a pressure transducer and a metric rod fixed to the ring. Electrical resistivity measurements were carried out, using the "time-lapse" technique, to observe the dynamics of infiltration/redistribution of water in the vadose zone. Hydrogeophysical data were acquired for long periods to gain a more complete understanding of subsurface flow. The observations were used to independently estimate travel times and infiltration rates using a numerical model.