Sustainability of the blue water footprint of crops

Agriculture is the largest water user and the driving force behind global water stress. While several studies have already assessed global green and blue water use in crop production at high spatial resolution, few studies have explicitly linked water scarcity to water use in the production of individual crops and assessed the sustainability of each crop production. We provide a detailed assessment of the sustainability and efficiency of the blue water use in global crop production. The study shows that 57% of the global blue WF is unsustainable. Close to 70% of the unsustainable portion of global blue WF is due to the production of five crops: wheat (27%), rice (17%), cotton (10%), sugarcane (8%), and fodder (7%). These crops have large unsustainable blue WF fraction ranging from 43% for rice to 68% for wheat. Countries with a significant proportion of unsustainable blue WF associated with crop production are primarily found in the Middle East and Central Asia. Qatar is at the top of the list, with about 71% of its blue WF being unsustainable, followed by Uzbekistan (68%), Pakistan (68%), and Turkmenistan (67%). Approximately 25% of the blue water can be saved globally by reducing the crop-specific WF to benchmark level.