Future global streamflow declines are probably more severe than previously estimated

Climate change and increasing water use associated with socio-economic growth have exacerbated the water crisis in many parts of the world. Many regional studies rely on Earth System Models that, however, do not fully exploit streamflow observations. Here we offer an observation-based approach to predicting streamflow change on the basis of the elasticity of streamflow to their climate drivers observed at 9,505 catchments across the globe. We show that near-future (2021–2050) global streamflow may be lower than predicted by Earth System Models, particularly in Africa, Australia and North America. The lower streamflow predicted here is due to smaller contributions from precipitation and stronger sensitivity of streamflow to changes in evapotranspiration, which is related to increased radiation energy and vapour transfer, and enhanced vegetation greening. Our estimate points towards the possibility that a future water crisis could be more severe than anticipated. Earth System Models are widely used for projecting future streamflow. The authors show that the models underestimate declines in global streamflow with climate change, indicating that a future water crisis could be more severe than previously estimated.