Extreme weather events brought on by climate change are leading to a deterioration in the quality of water in rivers around the world, warns a new study.
An international team of scientists collated data on rivers to show how extreme events like flooding, droughts, heatwaves and rainstorms affect the water quality.
The research team analyzed nearly a thousand cases of changes in river water quality and found droughts and heatwaves to be the most likely weather events to lead to quality deterioration.
The scientists also emphasized the need for further such research into the effects of extreme weather events on water supplies, due to them growing ever more frequent amid our warming climate.
The research team, led by Dr. Michelle van Vliet of Utrecht University in the Netherlands, says the increases in events like droughts and rainstorms are posing growing challenges both for the availability and quality of water.
However, according to the latest Intergovernmental Panel on Climate Change (IPCC) report, our collective knowledge of such changes is currently insufficient.
To combat this, an international group of scientists was formed to bring together a huge body of research on the water quality of rivers across the globe.
The researchers, whose study was published in the journal Nature Reviews Earth & Environment, analyzed a total of 965 cases of river water quality changes during extreme weather events such as droughts, heatwaves, rainstorms and flooding.
The team also analyzed long-term changes in climate over a number of decades.
Dr. van Vliet, an associate Professor at the Department of Physical Geography at Utrecht University, explained: “We looked at various water quality constituents such as water temperature, dissolved oxygen, salinity and concentration of nutrients, metals, microorganisms, pharmaceuticals, and plastics.”
The collaborative team’s analyses found that water quality tends to deteriorate in nearly three-quarters (68 percent) of cases of droughts and heatwaves and over half of rainstorms and floods (51per cent) and under long-term climate changes (56 percent).
During droughts, less water is available to dilute contaminants.
Conversely, rainstorms and floods tend to result in contaminants running off from land and into rivers and streams.
Improvements or mixed responses in water quality are also reported in some cases where mechanisms to counteract extreme weather events are used – such as when increased transport of pollutants is offset by more dilution during flooding.
Water quality changes can also be strongly driven by changes in river discharge and water temperature, land use and other human factors such as wastewater treatment.
“Understanding the complex interplay between climate, land use and human drivers, which together influence the sources and transport of pollutants is crucial,” Dr. van Vliet said.
The team also called for more data collection and studies of water quality in non-Western countries and emphasized the urgent need for a better understanding of changes in water quality during extreme weather events.
She added: “We need better monitoring of water quality in Africa and Asia. Most water quality studies now focus on rivers and streams in North America and Europe.
“Only then will we be able to develop effective water management strategies that can safeguard our access to clean water and ensure ecosystem health under climate change and increasing weather extremes.”
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