A quantitative assessment of mountain-front recharge from Alpine and Apennine areas to Po Plain alluvial aquifers has often been overlooked in previous studies and is therefore addressed in this research project through the study of two pilot piedmont areas (Brescia and Bologna).
The recharge assessment is performed using 1) endmember mixing models based on conservative tracers of water (water stable isotopes) and salinity (Cl/Br ratio) and 2) water balance calculations based on discharge measurements of mountain rivers. A one-year monitoring of 41 wells tapping the alluvial piedmont aquifers, 17 mountain springs/wells, 11 mountain rivers/streams and 3 rainwater collecting stations was carried out.
Results showed that the sources of groundwater recharge vary in the different areas and sub-areas depending on the hydrogeological features and the land and water uses. More specifically, in the moraine of Lake Iseo in the Brescia area (Franciacorta), recharge is given by the mixing of 1) surface mountain-front recharge (sMFR) from minor streams coming from the moraine hills, 2) local (plain area) precipitations and 3) surface-water-irrigation return flow. In the piedmont urban area of Brescia recharge is due to 1) focused mountain-block recharge (fMBR) from the Alpine alluvial aquifer of Val Trompia, 2) diffuse mountain-block recharge (dMBR) from the karst Alpine aquifer and 3) sMFR from the Mella River. In the carbonate area of Carso Bresciano recharge is mainly due to 1) dMBR from the karst Alpine aquifer and 2) surface-water-irrigation return flow. Concerning the Apennine area of Bologna, the alluvial fan aquifers of the Reno, Savena and Idice Rivers are recharged by (1) sMFR from the rivers and (2) local precipitations. Recharge from MBR appears negligible in most cases. Mixing models also showed that a relevant source of water for pumping wells in Bologna is deep fossil groundwater.
This project was funded by the European Union – Next Generation EU – PRIN 2022