Groundwater Management in the Northern Adriatic Coast (Ravenna, Italy): new strategies to protect the coastal aquifer from saltwater intrusion

The Emilia-Romagna Adriatic coast represents a strategic economic asset for Italy because of its important environmental, historical and tourist value. An efficient environment protection and water resource management in this coastal zone is difficult because of the many events that during the last century caused the ingression of large volumes of brackish and saline water in the coastal aquifer. River mouth enlargement to accommodate for tourist marinas has caused extensive landward saltwater encroachment along rivers and canals. Tourist establishments along the coastline have destroyed the original sand dunes continuity and their natural barrier effect to beach erosion and saltwater intrusion. Strong natural and artificial subsidence, induced by gas winning and deep groundwater exploitation, caused most of this territory to drop below mean sea level and have modified the river regime and the normal groundwater flow. In this situation, a drainage system is necessary to lower the water table level and keep the land dry, so that trees roots stay above the saturated zone of the aquifer. The drainage system management, however, has not accounted for the proximity to the sea. The result is an unstable phreatic aquifer that is not able to contrast saltwater intrusion and is not beneficial to maintaining a healthy pine forests and avoiding soil salinization. Water table and surface isosalinity maps have been created by monthly monitoring data. These data show watertables below sea level and groundwater salinization; well testing and geo-electric surveys provided a detailed lithological characterization and the depth of the brackish-freshwater interface. Analytical and numerical modeling (WATBAL, SUTRA, MOCDENS3D, and SEAWAT) were used to calculate the water budget and study how past and present human activities have affected the saltwater intrusion process and how the predicted future sea level rise will further degrade the aquifer. The feasibility and effects of some alternative actions such as controlled drainage, freshwater storage in ponds along the coast, artificial recharge, river bottom sills, optimization of the hydraulic infrastructure and coastal dune restoration have been examined. In addition, the interactions between surface and ground waters as a connected resource need to be further explored in order to find innovative strategies for coastal aquifer management. Finally, we stress how an integrated approach is necessary; history has shown that a disaggregated water management, the present fragmentation of water authorities and the lack of communications among different institutions and the stakeholders are the major threats to the coastal environment and its water resources.