Irrigation-induced precipitation as a water externality of agricultural production

Abstract Irrigation water lost through evapotranspiration is redistributed globally: physically, via atmospheric moisture transport and downwind precipitation, and virtually, embedded in traded crops. These pathways have traditionally been studied independently, leaving it unclear whether irrigation-induced atmospheric recycling compensates for or amplifies irrigation water use for food production and trade. By coupling agro-hydrological modeling of 148 crops with country-to-country atmospheric moisture transport and international trade data, we find that 72% of irrigation-induced evapotranspiration returns to land as precipitation (the remainder being lost to oceans), with 45% crossing national borders through the atmosphere, more than three times the volume redistributed through virtual water trade. Rather than offsetting trade-based dependencies, atmospheric transfers largely reinforce them: 73% of countries hold the same role in both networks, as net donors or net recipients. Water dependencies between countries therefore extend beyond trade to the atmosphere, an externality that current water governance and food security assessments fail to capture.