Groundwater Resources Management in Mountainous Areas: A Regional Scale Approach in Lombardy Region (Northern Italy)

Groundwater resources management and protection at a regional scale require the identification and definition of groundwater bodies (GWBs) that should represent the hydrogeological reference areas to evaluate the availability and quality of groundwater resources. In mountainous areas, groundwater resources are strategically important to maintain adequate water supply for human consumption and to preserve the functionality of (ground)water dependent ecosystems, also considering the expected growing demand and reduction of resources due to ongoing climate changes. Within this framework, this study presents a regional approach that could support public agencies and water companies to efficiently manage and protect the water resources in mountainous areas. A 3D hydrostratigraphic model coupled with a water budget evaluation and hydrochemical and isotopic fingerprints was developed to identify and delineate GWBs in a geologically complex Alpine environment. The 3D hydrostratigraphic model integrated the available geological maps and cross-sections and applied the current classification criteria for hydrogeological mapping to the bedrock units, respecting the geometry of their boundaries. The model accounts for the dominant groundwater circulation patterns through the geological units that compose the bedrock water reservoirs. GWBs were identified and verified through the inspection of the 3D hydrostratigraphic model combined with: i) the location of known springs, ii) the knowledge on groundwater circulation (e.g., speleological information), iii) the hydrochemical characteristics, iv) the location of recharge areas identified through isotopic analyses, v) the groundwater budget evaluation. Sixteen GWBs have been identified all over the 10.290 km² area, showing differences in storage capacity up to four times between GWBs mainly constituted of carbonate rocks and those prevalently composed of crystalline or terrigenous rocks. Groundwater quality in the study domain is generally excellent, with few exceptions. The results of this study allow to: i) identify the most Strategic Storage Reservoir in terms of quality and storage capacity; ii) evaluate the present ground- and surface water availability; iii) detect areas of interest for implementing groundwater monitoring networks; iv) recognise recharge areas of the most relevant springs, to implement protection strategies.