 Study assesses the blue water footprint of hydroelectricity, the water evaporated from man-made reservoirs to produce electric energy for 35 selected sites. The aggregated blue water. Footprint of the selected hydropower plants is 90 gm and lt, sup and gt, 3 and lta slash sup slash gt, year and lta sup and gt, minus 1. This is equivalent to 10% of the water footprint of global crop production in the year 2000. This article was authored by M. M. Mekonen and A. Y. Hoekstra.