Air Pollution Increases Water Flow in Rivers

You wouldn't think that air pollution has an impact on rivers, but it turns out that's exactly the case. Scientists have discovered that the amount of air pollution has a significant impact on the amount of water flowing through many rivers in the northern hemisphere.

The pollutants in this case are aerosols. Already, scientists have established that burning sulphurous coal up to the late 1970s led to additional aerosols in the atmosphere. With their reflective properties, these aerosols reduce the amount of sunlight reaching the Earth's surface, an effect known as "solar dimming."

As countries started to introduce clean air legislation and cleaner fuels, though, this solar dimming began to reverse. That's why scientists decided to examine the effect of solar dimming on river flows to see if it had any effect.

"We detect the impact of solar dimming on enhanced river flows over regions in the heavily industrialized northern extra-tropics," said Nicola Gedney, lead author of the new paper, in a news release. "We estimate that, in the most polluted central Europe river basin, this effect led to an increase in river flow of up to 25 percent when the aerosol levels were at their peak, around 1980. With water shortages likely to be one of the biggest impacts of climate change in the future, these findings are important in making projects for the future."

So how did this happen? As the sunlight was reduced, the rate of evaporation from the Earth's surface decreased. When the dimming began to reverse, though, reductions in river-flows occurred.

"This study involved using detection and attribution techniques which were able to show a link between aerosols and changes in river flows," said Chris Huntingford, one of the co-authors of the new paper. "These studies normally involve looking at how different factors affect temperature, but here we've been able to attribute this man-made influence to an environmental impact."

The findings reveal how the atmosphere can greatly impact the surrounding environment. Pollution, in particular, can change exactly how much water is available in a region.

The findings are published in the journal Nature Geoscience.