Wheat, rice, sugar, cotton and maize are among the essential internationally traded crops in the global economy. To produce these crops many countries rely on irrigated agriculture that accounts for about 70 percent of global freshwater withdrawals. One freshwater source is underground aquifers, some of which replenish so slowly that they are essentially a non-renewable resource. A new study by researchers at University College London and NASA’s Goddard Institute of Space Studies in New York City shows that 11 percent of the global non-renewable groundwater drawn up for irrigation goes to produce crops which are then traded on the international market. Two-thirds of the exported crops that depend on non-renewable groundwater are produced in Pakistan (29 percent), the United States (27 percent), and India (12 percent).
Lead author Carole Dalin from University College used trade data on countries’ agricultural commodities from the United Nations Food and Agriculture Organization. They then combined the results with a global hydrologic model — validated with ground information and NASA satellite data — to trace the sources of water used to produce 26 specific crop classes from their country of origin to their final destination.