Potential recharge areas of deep aquifers: an application to the Vercelli–Biella Plain (NW Italy)

Abstract

Deep aquifers typically serve as a key source of drinking water due to their good groundwater quality. Then the identification of deep aquifers recharge areas provides the local administration with a management tool to protect groundwater, through the implementation of legislative measures for the control of pollution sources. However, the location and size of recharge areas of deep aquifers are often difficult to define and generally require a large amount of data. The aim of this paper is to propose a method to identify potential recharge, throughflow and discharge areas of deep aquifers on a regional scale, due to their hydrodynamic features. As the proposed method identifies where deep-aquifer recharge can occur, but not the recharge rate, delimited areas are defined as “potential”. Particularly, the method analyses piezometric level differences between shallow and deep aquifers to understand groundwater flow direction. The areas where groundwater flow is downward are delimited as potential recharge areas of deep aquifers (PRADAs). The method represents a qualitative approach to the identification of PRADAs, because it permits to narrow down large plain areas extension, highlighting where potentially recharge areas are located. Then PRADAs location and shape can be defined effectively, expanding data sets and furthering analyses (hydrogeological reconstruction, hydraulic connectivity, hydro-chemical and isotopic methods…) in the identified areas. The hydrogeological setting investigated by this method is representative of many anthropized and groundwater-demanding plains around the world that require to be protected. Thus, the method represents a suitable approach for PRADAs’ identification in such settings, especially in low-income countries, where resource availability for studies and analyses is scarce. This method was then applied to a plain area of Northwest Italy, and the locations and sizes of potential recharge, throughflow and discharge areas of deep aquifers were identified on a regional scale.