Assessing Farm-Basin Feedback: Deficit Irrigation and Water Savings across the Mediterranean

In Mediterranean and arid environments facing increasing hydro-climatic pressure, irrigated agriculture is central to food security while placing strong pressure on limited water resources. In response, on-farm irrigation optimization, particularly regulated deficit irrigation and efficiency-oriented technologies, has demonstrated benefits in yield stability, water productivity, and farmer income. However, these improvements often produce unintended basin-scale effects, as efficiency gains do not necessarily translate into collective water savings and can undermine long-term water management objectives. Drawing on evidence from four ACQUAOUNT pilot sites (Italy, Tunisia, Jordan, and Lebanon), this contribution examines the trade-offs between farm-level optimization and basin-scale water management objectives. Using a narrative-based Decision Support Tool that integrates climate projections, hydrological modeling, agricultural water demand, and socio-economic evaluation, we assess how deficit irrigation interacts with allocation rules, sectoral competition, and ecosystem requirements under current and future climate conditions. Our analysis shows that in water-scarce basins, economically accessible water resources and productivity-driven incentives often lead farmers to reinvest efficiency gains into expanded or intensified water use, offsetting potential basin-level savings. These dynamics highlight a structural disconnect between agricultural decision-making and sustainable water governance. By disentangling these processes across contrasting contexts, we derive actionable recommendations to better align irrigation practices with basin management interventions. The results support Integrated Water Resources Management (IWRM) approaches that balance agricultural resilience, ecosystem preservation, and climate adaptation, explicitly accounting for cross-scale feedbacks in irrigated systems.