Evaluation of national and regional groundwater resources under climate change scenarios using a GIS-based water budget procedure

The present study investigates the impact of climate change on the availability of groundwater resources in Italy and in Campania region (Southern Italy). A 20-year average from 1996 to 2015 of annual water budget components (namely total precipitation, actual evapotranspiration, surface runoff and aquifer recharge) has been evaluated over a 1-km resolution grid and have been projected considering four climate change scenarios (from the Fifth Assessment Report of the United Nations Intergovernmental Panel on Climate Change) and three different future 20-year time periods (2020–2039, 2040–2059 and 2080–2099). The groundwater balance has been carried out on a yearly basis using the “Nationwide GIS-based regular gridded hydrological water budget” procedure, which has been developed by the Italian National Institute for Environmental Protection and Research (ISPRA). The different scenarios of groundwater resources have been compared and matched to the 20-year average of latest historical values related to the period 1996–2015, leading to interesting considerations about the future depletion of groundwater resources. Nationwide results have been compared with those of Campania region, in order to underline the significant differences of climate change impact on groundwater resources at local scale, especially in a typical Mediterranean climate where groundwater resources represent the main source of water for human needs.