Projected timelines of water depletion in world’s major irrigated agriculture hotspots

Water availability is a key limiting factor for crop production, with many regions worldwide already facing water scarcity exacerbated by population growth, urbanization, and climate change. Knowing how much water can be allocated for irrigation without depleting water resources or causing environmental degradation is essential under climate change conditions. The traditional method for assessing climate impacts involves comparing future periods to a reference period, but it lacks the temporal detail needed to attribute changes specifically to climate change and distinguish them from natural variability. The Time of Emergence concept is crucial for decision-makers, as it allows them to identify the optimal timing for implementing measures to adapt to climate change. This study investigates sustainable irrigation, namely the ratio between total water consumption and water availability, on a global scale throughout the 21st century. The analysis considers different climate models and warming scenarios. The results indicate that, at the ensemble level, runoff is projected to increase by 6% to 12% by the end of the century compared to the 2001-2010 baseline period for the SSP1-2.6 and SSP5-8.5 scenarios, respectively. Correspondingly, water scarcity is expected to worsen, with a 24% increase under the business-as-usual scenario. Our results identify where, when and how water scarcity will affect irrigated food production in the 21st century. Understanding available water resources and the timeframe beyond which sustainable irrigation cannot be ensured is vital for planning and managing measures to guarantee a stable and reliable food supply and preserve ecosystems in a rapidly growing population context.