Irrigation boosts precipitation on cropland for international trade through atmospheric moisture transport

Agriculture accounts for approximately 70% of global freshwater withdrawals, while around 20% of global cropland is irrigated and supports nearly 40% of total crop production. In an increasingly globalized food system, up to one-third of this production is traded internationally, redistributing the water embedded in crop production, i.e., virtual water, from producing to importing countries. Previous studies have extensively assessed the hydrological and socio-economic impacts of freshwater withdrawals embedded in food trade, focusing on both surface and groundwater resources. However, how irrigation contributes to agricultural production and consequent virtual water exports when returns on land as precipitation through atmospheric transport, is currently unexplored.

This study addresses this gap by quantitatively assessing to what extent irrigation for primary crop production in one country contributes to precipitation in other countries and how this precipitation subsequently supports crop production and trade. The methodology integrates agro-hydrological modelling of the crop evapotranspiration attributable to irrigation with harmonized bilateral datasets on atmospheric moisture transport and virtual water trade.

Specifically, we use the agro-hydrological model waterCROP to estimate the blue water demand associated with 167 primary crops, scaling total virtual water volumes from the CWASI database to blue virtual water flows. These estimates are coupled with atmospheric moisture tracking data from the RECON dataset, a processed version of the Lagrangian output of the UTrack model reconciled with ERA5 reanalysis data for the period 2008–2017. The analysis is conducted at the global scale for the representative year 2013, ensuring consistency between atmospheric moisture flows and virtual water trade datasets.

By coupling these bilateral networks, we construct a new set of water teleconnections that explicitly links agricultural water use to atmospheric moisture transport, precipitation, crop production, and trade. Within this framework, we assess how irrigation in one country contributes to precipitation in other countries, and if this contribution alleviates, compensates, or worsens the need for freshwater withdrawals. This allows us to identify synergies and trade-offs in the geographic redistribution of precipitation originating from irrigation and the associated water use embedded in the international trade of crops.

By revealing how the precipitation originated from the evapotranspiration of irrigated crops contributes to agricultural production beyond national borders, the analysis highlights previously overlooked feedbacks between water use, atmospheric moisture transport, and food trade.