Land subsidence due to groundwater exploitation in Italy

Problems

• Land subsidence in Italy, especially in the capitals of Venice and Bologna, is a problem that came to light at the beginning of the 1960s. Venice was more frequently subjected to acqua alta events. This case history is surely one of the most famous in the world, due not to the amount of sinking but to the special prestige of the city, which risks disappearing into the lagoon. 
  
  The physical structure of Venice is characterized by the presence of historic buildings – some of which were constructed more than six centuries ago – in direct contact with the lagoon water and with the ground level only a few tens of centimeters above normal high tide level.

• Cause of land subsidence in Venice and Bologna

  Progressive exploitation of the six artesian aquifers in the upper 350 m of the 1000-m-thick unconsolidated Venetian Quaternary formation began in the 1930s, with the first industrial installations growing with the post-war industrial development. 
  
  The subsidence rates (1-3 mm/yr) recorded recently along the coastline and at the furthermost northern and southern lagoon boundaries are correlated with local processes, such as restricted groundwater exploitation and more active sediment consolidation caused by these areas' subsoil depositional history.
  
  Additionally, the exploitation of natural gas reservoirs contributed to land subsidence, although not nearly as much as related to groundwater extraction. 

• The Impact

  In addition to structural damage, land subsidence in Italy has increased flood susceptibility and risk. As the land sinks, areas previously safe from flooding become prone to inundation, especially during storm surges. This affects residential areas and agricultural lands, leading to economic losses and food security concerns.
  
  Furthermore, land subsidence has a permanent impact on aquifer-system storage capacity. As the ground sinks, the space available for storing groundwater reduces, which can exacerbate water scarcity issues. This is particularly concerning in regions that rely heavily on groundwater for domestic, agricultural, and industrial use.

• Conclusion

  Mitigation measures have been implemented in some areas, such as reducing groundwater extraction and reinforcing infrastructures. However, the extent of subsidence and its impacts are still not fully known for many locations, highlighting the need for continued research and monitoring.
  
  Overall, the impact of land subsidence in Italy is a stark reminder of the consequences of human activities on the environment. It underscores the importance of sustainable resource management and the need for proactive measures to protect communities and ecosystems from the adverse effects of this geological hazard.