Globally widespread and increasing violations of environmental flow envelopes

Abstract. Human actions and climate change have drastically altered river flows across the world, resulting in adverse effects on riverine ecosystems. Environmental (EFs) emerged as a prominent tool for safeguarding ecosystems, but at global scale, assessment of EFs is associated with high uncertainty related to hydrological data EF methods employed. Here, we present novel, in-depth using environmental flow envelopes (EFEs). Sub-basin-specific EFEs are determined approximately 4400 sub-basins monthly time resolution, their derivation considers methodological uncertainties global-scale studies. In addition lower bound discharge based existing methods, introduce an upper EFE. This enables areas be identified where streamflow has substantially increased above natural levels. Further, instead only showing whether violated over period, quantify, first time, frequency, severity, trends EFE violations during recent historical period. Discharge was derived from model outputs ISIMIP 2b ensemble. We use pre-industrial (1801–1860) quasi-natural together suite estimate EFEs. then compare (1976–2005) assess These most commonly manifest insufficient low-flow season, fewer intermediate-flow few high-flow season. The widespread occur half world more than 5 % months between 1976 2005, which double compared mainly been increasing, will likely continue future projected hydroclimatic changes increases anthropogenic water use. Indications extreme through relatively scarce dispersed. Although local fine-tuning necessary practical applications, further research coupling quantitative ecosystem responses scale required, provide quick globally robust way determining allocations sub-basin inform policies resources management.