Large variations in global irrigation withdrawals caused by uncertain irrigation efficiencies

Abstract An assessment of the human impact on global water cycle requires estimating volume withdrawn for irrigated agriculture. A key parameter in this calculation is irrigation efficiency, which corrects fraction lost between withdrawals and crop due to management, distribution or conveyance losses. Here we show that efficiency used models flawed it overlooks ambiguities partial efficiencies, technologies, definition ‘large-scale’ areas managerial factors. Once accounted for, these uncertainties can make withdrawal estimates fluctuate by more than one order magnitude at country level. Such variability larger leads extreme values caused related with climate change. Our results highlight need embrace deep prevent design shortsighted policies river basin-water-agricultural interface.