Population growth, socio-economic development, and climate changes are placing increasing pressure on water resources (Agha Kouchak et al., 2015; Distefano and Kelly, 2017).
Global water demand is expected to continue increasing at rate of 1% per year until 2050, accounting for an increase of 20%–30% above the current level of water use (WWAP, 2019).
Agriculture, mainly devoted to the production of food, accounts for about 90% of the global freshwater use and nearly 70% of global water withdrawals, representing the human activity that requires the largest volumes of water resources (Falkenmark and Rockström, 2004; FAO, 2011).
The nexus between water and food received a recent burst of attention with the introduction of the water footprint concept, which has become widely used in several multidisciplinary contexts. The water footprint (WF) measures the volume of water used to produce a good along its supply chain, whereas its unit counterpart (water footprint per unit weight of output), or crop water footprint (CWF), represents a useful indicator of water use efficiency (eg, Hoekstra et al., 2011, D’Odorico et al., 2019).
The CWF is extensively used to quantify the water virtually embedded in the agricultural goods exchanged through international trade, the so-called virtual water trade (Allan, 1998; Hoekstra, 2005). Both CWF and WF are affected by a marked spatial and temporal variability. The spatial variability of crop water footprint has been studied extensively in the recent literature (eg, Mekonnen and Hoekstra, 2011; Tuninetti et al., 2015), highlighting marked differences worldwide, which are determined by different climatic parameters.