Présentations Colloques

The deep aquifers represent one of the most important supply of drinking water. They are involved in intermediate and regional flow systems and are characterized by a different chemical composition compared to shallow one. Their groundwater are constantly renewed in the recharge areas of the deep aquifer (shown below as RADAs), where groundwater flow is downward directed, from the topographic surface to the deep aquifer, passing through the shallow one. This flow is able to transfer not only water but also pollutants from the ground surface to the deep aquifer. Consequently, the identification and safeguard of RADAs represent one of the most important prevention measure against the damage of water quality. Whereas the recharge areas of the shallow aquifer correspond with all the topographic surface, the RADAs are represented by a limited sector of it. Unfortunately their identification on a regional scale is not easy because it requires many hydrogeological and chemical data. These data are lacking in most of the Piedmont Region (NW Italy)+ thus a methodology for mapping RADAs was proposed, based on easily available data. More specifically the evaluation of the length of regional flow system, from its starting point to the discharge area of deep aquifer, was used. Indeed the size of the RADAs can be considered as a percentage of the length of the regional flow system. The size of these areas was modified in a second step according to including and excluding criteria, e.g. the water head difference between the shallow and the deep aquifers and the outcropping of the hydrogeological units hosting the deep aquifer. **After the identification of RADAs in the Piedmont plain using this simplified approach, RADAs distribution and size were compared with recharge areas identified in a large portion of the plain (Vercelli plain) by previous studies that used hydrogeological data. The comparison highlighted that the differences of size of RADAs are very little, thus supporting the validity of this approach.**