Major volcanic eruptions can have a significant effect on the flow of the biggest rivers around the world, researchers said.
A team from University of Edinburgh did the research to better understand how big volcanic eruptions, which can trigger a shortage of rainfall, can impact rivers, Xinhua news agency quoted a university statement as saying.
Their findings could help scientists predict how water availability in regions throughout the world might be affected by future eruptions, it added.
The study focuses on the impact of a process in which volcanoes give off aerosol particles that reflect sunlight, cooling the atmosphere and leading to reduced rainfall.
The team analysed records of flow in 50 major rivers. Their study spanned the dates of major eruptions, from Krakatoa, Indonesia in 1883 to Pinatubo, the Philippines in 1991.
Eruptions were followed a year or two later by reduced flow in some rivers. In general, this was found in tropical regions and northern Asia, including the Amazon, Congo and Nile.
However, flow increased in some sub-tropical regions. Areas affected included the southwest of the US and parts of South America.
The Amazon is in a sparsely populated area, so reduction in its flow may have little impact. However, for rivers with high levels of human dependence, such as the Nile, loss of flow could have more impact.
"Our findings reveal the indirect effect that volcanoes can have on rivers, and could be very valuable in the event of a major volcanic eruption in future," researcher Carley Iles said.
The study, published in Nature Geoscience online on Monday, was supported by the British Natural Environment Research Council and the European Research Council.
