HYDROGEOPHYSICAL APPROACH TO MEASURE HYDRAULIC PARAMETERS ON UNSATURATED ROCKS

摘要

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.