Présentations Colloques

We propose an application of a methodology to obtain a quantitative estimation of the horizontal component of the Darcy velocity by using analytical models of interpretation of heat transport by advection and conduction in permeable horizons. This study is based on the collection of groundwater temperature data, recorded in boreholes, in which the heat transfer is affected by both advection and conduction, with an important contribution by the seasonal climatic oscillations on temperature distribution in the first several meters of the subsurface.**The thermometric measures were collected in boreholes, with an average depth of approximately 30 up to 50 meters, by the means of a probe equipped with sensors of depth and temperature, with 0.01degree Celsius sensitivity.**Thermal logs show a trend characterized by temperature fluctuations linked to seasonal climatic change in the first depth meters, while the slightly concave profiles suggest a preferential horizontal groundwater movements of relatively warmer water, for greater depth.**We select the City of Turin (NW Italy) where an important shallow aquifer occurs, as an example of application of the methodology. The shallow subsoil of Turin city essentially consists of Pleistocene outwash sediments linked to Alpine watercourses forming wide fans, consisting of gravel and sand. These fans are cut by erosional scarps linked to the present incision of the Po River, partially filled by Holocene fluvial sediments. The shallow aquifer, that generally follows the topographic surface, shows a thickness ranging between 20 and 50 meters. **The application of this method to thermometric data only affected by seasonal fluctuation returns groundwater velocities with differences up to 4 orders of magnitude, suggesting this method is not applicable. On the contrary, the application of the analysis of the data collected below the seasonal fluctuations depth range, returns groundwater velocities of about 10^-5 – 10^-6 m s.**