It’s not only the availability of water but also its quality that is under threat due to climate change worldwide, an international group of scientists have said after analyzing river water quality. They showed that in most cases water quality tends to deteriorate during droughts and heatwaves (68%), rainstorms and floods (51%) and under long-term changes in climate (56%). During droughts, less water is available to dilute contaminants, while rainstorms and floods generally result in more contaminants that run off from land to rivers and streams, said the study published in Nature Reviews Earth & Environment.
The study further said that as these events become more frequent and severe due to climate change, ecosystem health and human access to safe water may be increasingly under threat and underlined the urgent need for a better understanding of water quality changes during extreme weather events, and the mechanisms underlying this.
“Climate change and increases in drought and rainstorms pose serious challenges to our water management. Not only is the availability of water under pressure, but also its quality. However, according to the most recent IPCC report our current understanding of this issue is inadequate,” noted the research led by Dr Michelle van Vliet of Utrecht University.
The team analysed 965 cases of river water quality changes during extreme weather such as drought, heatwaves, rainstorms, and flooding, as well as under long-term (multidecadal) changes in climate. “We looked at various water quality constituents such as water temperature, dissolved oxygen, salinity and concentration of nutrients, metals, microorganisms, pharmaceuticals, and plastics,” said van Vliet.
Improvements or mixed responses in water quality are also reported for some cases owing to counteracting mechanisms, for example when increased transport of pollutants is offset by more dilution during flood events, said the study.
Water quality changes are strongly driven by changes in river discharge and water temperature. Land use and other human factors such as wastewater treatment also shape how this plays out. “Understanding the complex interplay between climate, land use and human drivers, which together influence the sources and transport of pollutants is crucial” added van Vliet. The research also calls for more data collection and studies of water quality in non-Western countries. “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”.