Climatic characterization and response of water resources to climate change in limestone areas: some considerations on the importance of geological setting

This work analyses the response of springs fed by karst/fractured limestone aquifers, extensively outcropping in Central Italy, to climatic variations which in this area is represented by a general decrease in annual and winter precipitation. It is shown how groundwater regime, the discharge of springs and their response to climate change depend to a great extent on the geologic and structural setting of the system. Some mountain springs of Central Italy are “local systems” representing the “overflow” of a “deeper regional flow” feeding larger “base springs”, often of poor quality. A dynamic groundwater divide separates the recharge areas of base springs from those of local springs: if, due to low recharge, the piezometric surface lowers, the watershed moves towards systems located at higher altitudes, reducing their recharge areas. Therefore, local springs connected to a base flow are more vulnerable to climate change than those which are not. The Bagnara and Lupa springs, taken as examples, have similar mean discharges (about 120 l/s) and recharge areas with comparable lithological, topographical and climate characteristics. Nevertheless, only the discharge of Bagnara, which is connected to a regional flow, fell dramatically during recent prolonged drought periods (e.g., 2001-2003 and 2006-2007).