Updating the water budget of the Gran Sasso carbonate fractured/karstified aquifer (Central Italy) for a sustainable management of groundwater resources

Karst aquifers are fundamental in the water supply of European countries, where outcrops of carbonate rocks are very common, providing abundant groundwater resources. The Gran Sasso karst aquifer, selected as representative study area for Italy in the EU-funded KARMA project, is characterized by both high percentage of withdrawals for drinking purposes and significant interaction between groundwater and underground works. The recharge evaluation of the aquifer has been carried out considering the 2001–2020 monitoring period, comparing three different methods: the Turc and APLIS methods, on annual scale, and the Thornthwaite method, on monthly scale, territorially distributed by 100 x 100 m cells on GIS basis. The total recharge considers not only rainfall but also the contribution of snow melting on infiltration. The results show similar mean recharge values in 2001–2020 for all methods, corresponding to 19.9, 18.5, and 19.4 m3/s, respectively, from Turc, Thornthwaite, and APLIS methods. A significant contribution to recharge from snowmelt has been confirmed (3.2 m3/s included in the above-mentioned values). These values can be considered reliable with respect to real discharge of the regional aquifer. The obtained results can be used to provide updated information to the drinking water companies for a suitable management of the available resource.