Leveraging irrigation–groundwater interactions for climate change adaptation: results from an Ag-MAR application in a complex agri-urban setting

Agricultural managed aquifer recharge (Ag-MAR) harnesses agricultural settings and practices to infiltrate additional water replenishing groundwater systems. Can this method be used as an adaptation measure to current and future climate changes, posing a threat to water resources availability worldwide? Which are its requirements and limitations in an agri-urban context, characterized by a coexistence and sometimes a conflict of ecosystems and human activities with their needs and risks?

To address these questions, a two-year field experiment was conducted near Milan (Northern Italy), a densely urbanized area that still hosts intensive agricultural activities. In the area, and throughout the Po plain, summer crop water demand is met through surface irrigation, diverting river and stream water via a capillary network of canals. By providing additional water to the aquifer during autumn and winter, periods of high surface water availability, the enhanced groundwater reserves could be managed to cover the demand during hydrological droughts, avoiding the need for new reservoirs and their associated impacts on the water cycle.

The existing canal network served as the infrastructure for the experiment: during the 2023-2024 and 2024-2025 winters, water was diverted into canals and onto agricultural fields with the collaboration of local farmers, while groundwater levels and groundwater-dependent ecosystems were monitored. The collected data was then utilized to build a numerical groundwater flow model (MODFLOW) and an agro-hydrological model (IdrAgra), capable of estimating groundwater recharge through the simulation of irrigation management and irrigation-groundwater interactions, even under climate change conditions. Outputs (precipitation, temperature, humidity) from three regional circulation models were downscaled to generate a cascade of scenarios: future surface water availability and irrigation diversion, groundwater recharge, and groundwater levels. Multiple Ag-MAR configurations were then tested to assess their effectiveness in increasing groundwater storage and water table levels, while balancing infiltration targets with canal system capacity and minimizing risks to underground infrastructure.

We found that the spatial distribution of the irrigated fields plays a key role in the net groundwater storage increase, since groundwater-dependent ecosystems (lowland springs locally known as fontanili) scattered around the area can drain part of the additional recharge. Despite the losses, the measure increases the water available for the following summer months, enabling emergency withdrawals in case of drought. Results indicate that, even using only the volumes applied during the field tests, well below the system’s full potential, Ag-MAR could have supplied approximately 20% of the unmet water demand recorded in the study area during the 2022 drought.  This contribution increases under the scenarios considered. These findings provide a basis for regional authorities and local communities to develop long-term strategies for implementing Ag-MAR as an aquifer-based climate change adaptation measure.

This research was carried out as a Pilot Action of the MAURICE Interreg project (CE0100184).