At the IAH 2026 World Groundwater Congress – the 53rd Congress of the International Association of Hydrogeologists, held in Budapest from 14 to 18 September 2026 – Francesca Lobina presented, on behalf of the University of Cagliari team, partner of the NPP-SOL project, preliminary results from the Italian case study. The oral contribution “Nitrogen dynamics and natural attenuation in the unsaturated zone: insights from a high-resolution study in the Arborea NVZ (Italy)” was part of session 1.8, “Environmental tracers to investigate the anthropogenic impacts on groundwater” (https://iah2026budapest.com/program/#session-1-8).
Monitoring activities carried out in the Arborea Plain (Sardinia, Italy) are providing new insights into how irrigation water and nitrates move through the soil and groundwater system in this intensively farmed area.
The study focuses on an experimental site equipped with a woodchip bioreactor and a network of monitoring wells, or piezometers, installed at different depths. These instruments make it possible to follow changes in groundwater levels and water chemistry in both shallow and deeper parts of the aquifer. The monitoring is complemented by lysimeters, which collect water as it moves through the unsaturated soil, and by stable isotope analyses that help identify the origin and pathways of groundwater recharge.
The results show that irrigation plays a major role in groundwater dynamics. During the summer irrigation season, water levels in the shallow monitoring wells rise even when rainfall is very limited, providing clear evidence that part of the irrigation water infiltrates through the soil and contributes to groundwater recharge. At greater depth, groundwater levels may instead decrease because of seasonal pumping. However, chemical data show that irrigation-derived water and nitrate can still reach the deeper groundwater system.
These findings have led to an important revision of the hydrogeological conceptual model of the area. Rather than two completely separated aquifers, the subsurface appears to consist of a regional groundwater body overlain by discontinuous clayey and silty layers. Temporary perched shallow groundwater bodies can develop above these layers, while water can still move laterally and gradually percolate towards the deeper aquifer. Measurements from newly installed monitoring wells at different locations further support the hydraulic continuity of this system.
The study is part of the research carried out within the framework of the NPP-SOL project, part of the PRIMA Programme supported by the European Union.
