Rice is unique amongst major crops in that it can grow in flooded
conditions. Irrigated (flooded) rice is responsible for most rice production
worldwide, the 79million ha of irrigated lowland rice produces
75% of annual global output (IRRI, 2013). This rice has been estimated
to use 34–43% of global irrigated water, or 24–30% of the total freshwater
withdrawals (Bouman et al., 2007b). Water footprints of rice can
vary from 1.5–7 t water kg rice−1 (Aldaya et al., 2010; Mekonnen and
Hoekstra, 2014).