GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 3.2 ___ GNGTS 2023 DC and FDEM monitoring of the salt wedge on the Po di Goro river (Italy). P. Boldrin 1 , A. Bondesan 2 , F. Droghetti 1 , E. Ferrari 1 , G. Fornasari 1 , F. Neri 2 , E. Rizzo 1 1 University of Ferrara, Ferrara, Italy 2 Consorzio di Bonifica Pianura di Ferrara, Italy The climate change is heavily affecting our earth and the coastal zone is strongly sensitive to this changing. Rising seas will increase the contamination of the coastal freshwater supplies with salt water and they are controlling factors on the saltwater penetration in the delta system. The delta systems are characterized by complex dynamic between freshwater coming from continent and saltwater. The decrease in rainfall, both in terms of quantity and in terms of time periods, the lack of considerable snow accumulations on mountains and the continuous withdrawal of water resources for agricultural and industrial use produce a scarce recharge of the system for longer and longer periods. Consequently, the upstream extent of the mixing zone leads to an increase of the salt content in aquifers and surface waters. These conditions can hinder the water use for irrigation purpose leading to salinization of soils. This summer all the world’s news reports showed the Po River saltwater intrusion crisis, the Italian’s largest river delta system is affecting seawater penetration endangering the sustainability of the freshwater resources. The Po River delta is developed out of the Adriatic Sea. The dynamic advancement of the Po River delta, which is quite simple and highlights its dynamic in terms of geomorphology and kind of sediments (from sand to silt and clay). The saline wedge in the Po Delta area defines salinisation of groundwater and the soil. In most of the aquifer, the WT is below water level, which suggests that the aquifer is in unstable hydrodynamic conditions. These conditions allow for the active ingression of seawater from the east because the hydraulic head is not sufficient to avoid water to flow inland from the sea. The typical approach to detect chemical-physical parameters (i.e. electrical conductivity-EC) is the multiparameter probe for water quality, but with a punctual acquisition system is not simple to monitor a very long river (> 50km). Therefore, the research group proposed a fast geophysical approach for the monitoring of the saltwater penetration affecting the Po di Goro River, that is one of the Po river branches. Two geophysical methods, ERT and EM profiling, were applied detecting the water salinity in the river and its dynamic iteration with the subsoil around the riverbanks. The field activities are planned in two different periods (July and October 2022). Two Electrical Resistivity sections and two long EM profiles were carried out in different area along the Po di Goro river (fig.1). Moreover, a “moving boat” approach was applied to monitor the lifting of the saline wedge, where a multiparametric probe was used. The ERT sections highlighted how