 This study examines the effects of different methods on estimating environmental flow requirements, EFRs, in global water scarcity assessments, and finds that the range of estimated EFRs can significantly affect the area and population under water scarcity. The study highlights the need for more consistent and accurate estimates of EFRs to produce reliable water scarcity assessments. This article was authored by Xingcai Liu, Wenfeng Liu, Liu Liu, and others.