Abstract
The coastal aquifers of the Mediterranean region are highly susceptible to seawater intrusion due to a combination of challenges such as land subsidence, high aquifer permeability, urbanization, drainage, and an unsustainable use of water during the dry summer months. The present study is focused on a statistical analysis of groundwater data to evaluate the spatial changes of water level and electrical conductivity in the coastal phreatic aquifer of the Emilia-Romagna (Northeast Italy) for the period from 2009 to 2018. Data from 35 wells distributed across the entire regional coastal area are used to establish a temporal trend, as well as correlations between salinity, water table level, and rainfall. Water table and salinity distribution maps for the entire study area are discussed regarding surface geology and water management. Most of the wells are in the beach wedge sand unit, which allows for easy connectivity between groundwater and surface water. Surface water and groundwater salinization are enhanced along the surface water bodies connected to the sea. The lowest water table level occurs in the western and northern parts of the study area, because of the semiconfined behavior of the aquifer. Only in the northernmost, close to the Po River, and in the southernmost parts of the study area does the groundwater remain fresh for the whole period considered due to river aquifer recharge. In the rest of the region, the thickness of freshwater lenses, where present, is less than 4.5 m. The existence of a water table level below sea level and high saline water at the bottom of the aquifer in most of the study area suggest that the aquifer is in unstable hydrodynamic conditions and groundwater quality is not fit for human consumption or for irrigation. This study is the first to provide a regional overview of the state of groundwater level and salinization within the coastal aquifer of the Emilia-Romagna Region; it also suggests that, overall, the salinization trend has slightly decreased from 2009 to 2018.
Highlights
Water in the coastal zone is crucial for life, but its availability at a sustainable quality and quantity is challenged by population growth, tourism, land subsidence, agriculture, and climate variability
This research assesses the distribution of water level and salinization at the regional scale in the coastal aquifer of the Emilia-Romagna region (Northeast Italy) and evaluates their trends in time during the period 2009–2018
The results show that the presence of freshwater in the coastal aquifer is mainly controlled by strong seaward-directed hydraulic gradients, a good connectivity between aquifer and high discharge rivers, as well as by the presence of a coastal dune systems without pine forests
Summary
Water in the coastal zone is crucial for life, but its availability at a sustainable quality and quantity is challenged by population growth, tourism, land subsidence, agriculture, and climate variability. Saltwater intrusion into coastal aquifers by rising seawater levels is an example of how climate change impacts water quality. In this case, shallow coastal aquifers are at greatest risk. Among the factors causing coastal aquifer salinization, water drainage driven by a sinking topography is so important in lowering the hydraulic head and favoring saltwater up-coning (seepage), the area will experience negative effects on coastal groundwater resources and freshwater availability as long as land subsidence continues in the future. Based on the available data, which span a period of almost ten years (2009–2018), we want to establish if there is any trend in water table and groundwater salinity data We tackle these issues by considering the effects of the climate.
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