Quantifying irrigation-driven recharge in a complex urban-agricultural system: the case of Milan, Italy

<jats:p>Groundwater resources are influenced by a complex interplay of natural processes and anthropogenic activities. In the context of accelerating climate change, the availability of tools able to allow the implementation of robust and evidence-based resource management policies are increasingly necessary. A particularly relevant application of this approach lies in assessing how shifts in agricultural policy may influence water availability. This study presents an advanced unsteady-state numerical groundwater model for Milan metropolitan area, located within the Adda-Ticino basin in Northern Italy. The model, built with MODFLOW-NWT and subjected to a global sensitivity analysis, was calibrated over a five-year period (2014–2018) and was then used to assess the potential effect of irrigation practice changes. Results highlight the substantial role of irrigation in sustaining groundwater levels, with irrigation accounting 57% of average yearly recharge. Scenario simulations show that reductions in irrigation recharge (15, 30, and 50%) could lead to significant groundwater level declines, particularly in agricultural zones surrounding Milan but also extending to the city area. The model is a useful and robust decision-support tool for water authorities, allowing them to assess policy impacts and support the development of sustainable water management plans under changing climatic and anthropogenic drivers.</jats:p>