Underground temperature logs for wellfield monitoring

The study of groundwater flow largely benefits of numerical modeling aimed at searching a more sustainable exploitation of water resources based on the knowledge of the lithostratigraphic setting and information on the aquifer geometry and dynamics from well data. Continuous monitoring of holes often characterizing well field, represents a hardly practicable solution implying high costs. Alternatively, the analysis of borehole temperatures may improve the local hydraulic characterization and supplying estimates of groundwater flow velocity. The purpose of this study is to evaluate how borehole thermal logs can contribute to the implementation of a local groundwater flow model. As an example, we study the Maggiore Valley area, located in the Piedmont hilly region (NW Italy), whose main well field supplies drinking water to a wide area and the population of about 100.000 people. The increasing demand of water has led to the overexploitation of the Maggiore Valley groundwater resources, over the past decades, causing progressive lowering of piezometric level, spatial reduction of the artesian zone, localized land subsidence and damage to wells. The piezometric head reduced of about 50 m from 1920 to present-day. The new hydrogeological data inferred with the thermal method can give further constraints for the implementation of groundwater numerical modeling.