Multidecadal climate change was shown to have increased water temperatures and algae levels in 56 per cent of studies, which is partly responsible for a general decrease in dissolved oxygen concentrations in river water.

"The severe effects climate change is already having on water quality globally are very concerning. Previous climate change predictions flagged this, but unfortunately, we are now seeing these extreme events play out across the world," said Environment Institute member, Associate Professor Luke Mosley, who participated in the research.

"Rivers are intrinsically important ecosystems but also provide key water sources for drinking water and agriculture. Poor quality water can result in the river water being unsuitable for these uses."

"The severe effects climate change is already having on water quality globally are very concerning. Previous climate change predictions flagged this, but unfortunately, we are now seeing these extreme events play out across the world."

"Most water quality studies now focus on rivers and streams in North America and Europe. We need a better monitoring of water quality in Africa and Asia," said Dr van Vliet.