Dynamic 3D modelling of the unconfined aquifer of the River Marecchia alluvial fan (Rimini)

Aquifers play a relevant role in the mitigation of the risk due to the occurrence of drought events in the Emilia-Romagna region. In fact, their capability to store relevant volumes of water and the long time span between meteorological and groundwater droughts make aquifers an essential resource during dry periods. To mitigate the risk induced by water scarcity, in 2014 a managed recharge experiment was carried out on the River Marecchia alluvial fan. In detail, an additional volume taken from the river was diverted into a quarry lake. The lake is an outcrop of the aquifer, therefore an increase in the lake water volume produces a corresponding increase of the piezometric level in the aquifer, and therefore larger groundwater availability. Several international experiences on the management of aquifers for civil and agricultural water supply have shown the value of the information that can be derived by running groundwater simulation models. In particular, MODFLOW, an open access groundwater simulation model developed by the United States Geological Survey, is widely applied. The purpose of this work is to apply MODFLOW to study solutions for managing artificial recharge in the River Marecchia alluvial fan. In particular, a previous application of MODFLOW by the Regional Agency for Prevention, Environment and Energy of Emilia-Romagna (ARPAE) has been repeated by using a different model interface, ModelMuse, and additional climatic scenarios. The work confirms the potential benefits that can be provided by a groundwater simulation model for optimizing aquifer recharge. The application confirmed that recharge may be very successful in this specific case for mitigating the impact of water withdrawals.