More than the mean—A note on heterogeneity aspects in the assessment of water footprints

Water footprints for a crop produced in a specific country are often provided as mean values. However, mean values do not account for the spatial heterogeneity of water footprints within a country that is caused by heterogeneous climate conditions and production techniques. To sufficiently inform decision makers, the underlying heterogeneity should thus also be presented. We provide an illustrate example of seed cotton production in 19 regions in Brazil and China. Even though grey water footprints in Brazil are on average smaller, it also contains the highest possible grey water footprint across all regions. To avoid misleading inference on water footprint estimates, their spatial heterogeneity should be indicated. This will enable decision makers to consider trade-offs between average values and potential extremes.