Volcanic eruptions can reduce flow of major rivers by as much as 10%


Volcanic eruptions may have consequences on the flow of major rivers – mostly a negative one – as scientists have found that they can cause a reduction in their flow by as much as 10 per cent.

We all know that volcanoes spew out tonnes of ash and all this ash forms ash clouds which block the sunlight in nearby regions. Researchers at University of Edinburgh set out to understand the effect of this ash and the aerosol particles released during the volcanic eruptions on rainfall in nearby regions.

Researchers reveal that these aerosol particle have a cooling effect on the atmosphere by reflecting the sunlight and this cooling effect causes a reduction in rainfall. When this happens, the subsequent effect is that there is a reduction in the flow of rivers of nearby regions. Researchers say that their findings could hold the key to predict water availability in regions throughout the world where volcanoes are active.

For the research, Carley E. Iles & Gabriele C. Hegerl of University of Edinburgh analysed records of flow in 50 major rivers. They specifically looked at records that spanned the dates of major eruptions, from Krakatoa in 1883 to Pinatubo in 1991. Researchers looked at the signals that could potentially identify the influence of volcanoes on the rivers in a specific region and then computer models to link rainfall with eruptions to predict where rivers were likely to be affected.

Researchers found that just a year or two after a volcanic eruption, there was reduced flow in some rivers in the region of the eruption. Generalising this scenario, researchers found that tropical regions and northern Asia, and included the Amazon, Congo and Nile were the most affected. However, there were instances where the flow increased and this was primarily because of the disruption to atmospheric circulation patterns. Areas affected included the south-west US and parts of South America.

Predicting how changes to river flow might impact on people is not straightforward, researchers say. 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.

The study is published in Nature Geoscience.