Quantifying irrigation-driven groundwater recharge through coupled agro-hydrological and groundwater modelling: an Ag-MAR case study from the MAURICE project

Groundwater recharge estimation remains a key challenge for the design of sustainable irrigation systems operating within complex territorial areas and ecosystem constraints, particularly under climate change, which alters water availability, precipitation regimes, and agro-hydrological dynamics. This study presents a coupled agro-hydrological and groundwater modelling framework specifically developed to quantify irrigation-driven recharge and to assess managed aquifer recharge adaptation measures under climate change scenarios. The framework integrates the agro-hydrological model IdrAgra with the numerical groundwater flow model MODFLOW and is applied to a highly urbanized region near Milan (representing the Italian pilot area of the MAURICE Interreg project - CE0100184). In this area, irrigation contributes to groundwater recharge at magnitudes comparable to or exceeding those of precipitation, as the most spread irrigation methods are surface and flood. Within this pilot action, winter irrigation was tested during two seasons (2023–2024 and 2024–2025) as an agricultural managed aquifer recharge (Ag-MAR) strategy, with the objective of evaluating its feasibility and effectiveness in enhancing groundwater availability during drought periods.

Detailed data on irrigation management, irrigation timing and daily channel discharges were collected both in winter and during the agricultural season and were then used to simulate the daily soil water balance in the vadose zone with the IdrAgra model. The resulting spatially and temporally distributed percolation fluxes were used as recharge inputs for the MODFLOW model, allowing the quantification of groundwater storage variations induced by the adaptation strategy. Both models were implemented on a common 100 m resolution grid covering approximately 326 km².

The project domain includes areas characterized by three distinct water management regimes: (i) non-irrigated areas, where groundwater recharge is driven exclusively by precipitation; (ii) areas managed by the Est Ticino Villoresi Irrigation Consortium, where structured irrigation networks and monitoring data allow irrigation-driven recharge to be quantified at the irrigation sub-district scale; and (iii) areas managed by individual users, where operational data are limited. IdrAgra was applied consistently across the entire domain, ensuring a coherent representation of crop growth, irrigation practices, soil water balance, and resulting groundwater recharge despite heterogeneous data availability.

The modelling framework was used to (i) quantify the effect of winter irrigation on groundwater recharge during the two experimental seasons, and (ii) evaluate it based on three different regional climate model projections (over the period 2026–2050), combined with alternative spatial distributions of winter irrigation.

Experimental results highlight that the percolation fluxes from the winter irrigated fields are relevant and model simulations show that extending this Ag-MAR strategy to sufficiently large areas a significant contribution to groundwater recharge is obtained. This study demonstrates the effectiveness of coupling agro-hydrological and groundwater models to represent irrigation-induced recharge processes, providing robust decision-support tools for the design and evaluation of Ag-MAR strategies under current and future climate conditions.