Analysis of groundwater rebound in the Milan Metropolitan area by hydrostratigraphic, groundwater quality and flow modeling

Groundwater plays a fundamental role in shaping the economic and the social health of many urban areas. Due to its relatively low-cost and generally high quality, groundwater has been widely exploited for private domestic, irrigational, and industrial use. However, industrial use has decreased dramatically in the last few decades leading to a groundwater level rise causing geotechnical and environmental problems. Many urban areas are currently suffering this situation with consequent concerns about damage to subsurface engineering structures, inundation of subsurface facilities, and the mobilization of contaminants. As results, in recent years it has been recognised that urban groundwater is a potentially valuable resource due to problems associated with its under exploitation. The objective of this thesis is to tackle four main issues: (i) developing a robust hydro-stratigraphic model and providing a comprehensive hydraulic parametrization of glaciofluvial aquifers, (ii) providing a hydrogeochemical characterization and the assessment of the groundwater quality status relative to baseline conditions in a complex framework (i.e. urban), (iii) monitoring groundwater level and understanding the spatial variability of groundwater recharge (i.e. effective rainfall recharge and canal infiltration) to unconfined aquifer in urban areas, and (iv) developing both a regional and a urban scale groundwater flow model for simulating future withdrawals and climate (i.e. recharge) changes, and mitigation measures scenarios. These issues are illustrated for the aquifers of the Milan Metropolitan area which can be considered an example of how urbanization and changes in withdrawals can pose some threats to availability and quality of the groundwater resource. In fact, groundwater resources in the Milan Metropolitan area (Northern Italy) has been heavily exploited for public and industrial supply. Since the 1970s, the water demand of industry has fallen (ca. 36%) causing a groundwater rebound up to 15 m in the unconfined aquifer. Despite the aquifers in the Milan Metropolitan area are an incredible groundwater resource for a very large population (5,181,192 people) and a highly industrialized area a comprehensive hydrogeochemical characterization, and a groundwater flow model capable to capture the overall groundwater dynamics (both in steady and transient state) based on a comprehensive hydraulic parametrization and reliable recharge inputs, are still lacking.