Integrating water quality assessment and circulation models for a sustainable management of a strategic carbonate system: Clues from the Mt. Nerone-Mt. Catria Ridge (Central Italy)

This study provides an updated hydrogeochemical characterization and circulation model of the Mt. Nerone-Mt. Catria carbonate ridge (NCCR) groundwater system, a vital water resource for the ∼360,000 inhabitants of the Pesaro-Urbino province (Marche Region, Italy). Chemical analyses of an extensive dataset of water samples revealed that they exhibit a Ca-HCO₃ composition with a relatively low Total Dissolved Solids (TDS < 400 mg/L), suggesting limited interaction with the surrounding carbonates and silicates, and short and shallow pathways. A few samples show SO₄-enrichments and higher TDS (up to 3350 mg/L), likely related to relatively deep flow paths interacting with the evaporitic Triassic Burano formation, while the presence of some Na-HCO₃ (TDS up to 1000 mg/L) waters suggests prolonged circulation within Na-rich terrigenous formations.

The Chemical Water Quality Index (CWQI) confirms that most NCCR waters are qualitatively good since the anthropogenic contamination is practically negligible, as testified by the low contents of nitrate and chloride. Nonetheless, a few mineralized springs display high CWQI values, indicating poor quality. The latter usually occur along the main fault systems and mix, at different degrees, with the low-salinity shallow Ca-HCO₃ waters. This implies that excessive groundwater exploitation might be able to pump the mineralized waters, thus increasing the risk of quality deterioration. This study underscores the importance of continuous monitoring and sustainable management practices to preserve the NCCR resource, especially under the effects of climate change and increasing anthropogenic pressures. Our integrated hydrogeochemical approach and the conceptual model of water circulation offer valuable insights into groundwater dynamics, and it can be applied to similar (karstic) systems worldwide.