Groundwater pumping and land subsidence in the Emilia-Romagna coastland, Italy: Modeling the past occurrence and the future trend

The Emilia-Romagna coastland south of the Po River delta, Italy, has experienced a dramatic land settlement mainly due to the large groundwater withdrawal related to the local economic and tourist development started in the early 1950s. Although the use of surface water has reduced the settlement rate over the last three decades, anthropogenic land subsidence still continues in a few kilometer wide coastal strip at a rate larger than the natural one. The occurrence is reconstructed since 1946 with the aid of advanced finite element flow and poromechanical models implemented with a realistically detailed geology of the regional shallow multiaquifer system. The models have been calibrated against the piezometric, leveling, and extensometer records observed over the last 50 years, and a land subsidence prediction in 2016 is performed. The results show that the extensive groundwater pumping that occurred in the past is most likely the main cause of the recent land settlement as well because of the delayed compaction of the clay aquitards comprised between the depleted aquifers. However, the available pumping data do not allow for a thorough understanding of the current local settlement process along the coastline, which is the most vulnerable area of the Emilia Romagna region from an environmental viewpoint. If the planned scenario of groundwater resource management will be implemented, anthropogenic land subsidence is bound to become a marginal problem for the central and northern portion of the Emilia-Romagna coastland.