Scientists discovered volcanic eruptions actually change the way the world's major rivers flow.

The new findings could help scientists predict how water availability in different regions will be affected by volcanic eruptions, which are also known to influence rainfall, the University of Edinburgh reported. A team of researchers took a closer look at how volcanoes release aerosol particles, that have the ability to block and reflect sunlight in a way that cools the atmosphere and reduces rainfall.

"Precipitation decreases over much of the globe following large explosive volcanic eruptions, particularly in climatologically wet regions. Stratospheric volcanic aerosols reflect sunlight, reducing evaporation, whilst surface cooling [stabilizes] the atmosphere and reduces its water-holding capacity. Circulation changes modulate this global precipitation reduction on regional scales. Despite the importance of rivers to people, it has until now been unclear whether volcanism causes detectable changes in streamflow given large natural variability," the researchers wrote in their study abstract.

In order to determine how this phenomenon affects water flow in large rivers, the researchers analyzed the flow of 50 major rivers. They looked at how this flow data corresponded with eruption events spanning from Krakatoa in 1883 to Pinatubo in 1991. The rivers were grouped by region to help keep track of which rivers would be influenced by which volcanoes, and used computer models to correlate rainfall with eruptions.

The findings showed that following eruptions in tropical regions, rivers tended to have a reduced flow for a period of about two years. In sub-tropical regions, river flow was observed to increase in some cases following a volcanic eruption. The phenomenon seen in sub-tropical regions is believed to be linked to atmospheric circulation patterns. 

Changes to rivers located in sparsely populated regions such as the Amazon will likely have little impact, but changes to the Nile and other rivers in high-populated areas could have serious consequences for those populations.

The findings were published in a recent edition of the journal Nature Geoscience.