An international team led by the Federal Institute of Technology ETH Zurich analysed data from 7,250 water measuring stations around the world to find that changes in river flow in the last 40 years could only be the result of climate change.

River flow is an important indicator of water availability. It depends on many factors related to land and water management such as the diversion of water for irrigation or the clearing of forests.

Until now globally visible changes in river flow had not been investigated using direct observations to determine whether they can be attributable to climate change or to water and land management.

The team led by ETH was able to break down the influence of various factors on river flow by analysing data from 7,250 water measuring stations. Computer simulations, using global hydrological models fed with observed climate data from the period studied (1971 to 2010), made it possible to analyse climate change alongside observed river flow.

In a second phase, additional water and land management were also included in their simulations in order to study the influence of these factors. This did not affect the result, however. “Changes in water and land management are evidently not the cause of global changes in rivers,” explained Lukas Gudmundsson, lead author of the study.

Their findings, published in the journal ScienceExternal link, show that river flow changed between 1971 and 2010 and that this was caused by climate change. The computer model simulations are consistent with the observed changes in river flow only when climate change is considered.

This is the first study that used direct observations to demonstrate that climate change has a globally visible influence on rivers. The hope is that the models developed and data collected, which is the largest global data set of river flow observations, could be used to inform measures on how to adapt to climate change.