Multi-Decade Isotope-based Analysis of Groundwater Dynamics in the Veneto Plain

Limited knowledge of subsurface hydrogeological characteristics often hinders the proper understanding of groundwater dynamics, especially in highly heterogeneous systems. In the portion of the Veneto plain (Italy) east of the Brenta river, extending from the pre-Alpine foothills to the Venice Lagoon, groundwater nitrate infiltration represents a major concern, also because of the relatively limited understanding of the hydrogeological setting. This lack of information makes it difficult to constrain sources, pathways, and travel times of the substance conveyed by groundwater from the unconfined aquifer in the high plain to the complex confined multi-aquifer system seaward.

To address these difficulties, we apply a multi-tracer approach. We analysed major ions along with isotopes of O, H, C, Sr, He and Ne in groundwater samples collected at thirty representative points distributed across the domain in 2025.

We compared the resulting isotopic interpretation with the outcomes of previous similar investigations carried in the same domain in 1973 and 2008. This multi-decadal dataset, spanning approximately 50 years provides valuable insights into temporal shifts in groundwater dynamics due to climate change and anthropogenic forcings. The improved conceptualization of the groundwater system resulting from this analysis will enhance our understanding of the nitrate fate in the Venice aquifer system. This, in turn, will provide a robust scientific basis for developing and implementing effective groundwater management and protection policies.