Climate change and increasing droughts and floods pose serious challenges to our water management. Not only the availability of water, but also its quality is under pressure. However, according to the IPCC’s latest report, our current understanding of this issue is inadequate.

To fill this gap, an international group of scientists combined multiple studies on water quality in rivers around the world. The study published today (September 12) Nature Reviews Earth and Environment, It shows that river water quality tends to deteriorate during extreme weather events. As these events become more frequent and severe due to climate change, ecosystem health and human access to clean water may be increasingly threatened.

Detailed studies

Dr. from Utrecht University. The study, led by Michel van Vliet, analyzed 965 cases of changes in river water quality during extreme weather conditions such as drought, heat, rain and floods, as well as long-term (several decades) climate change. . “We looked at different components of water quality, such as water temperature, dissolved oxygen, salinity and nutrient concentration, metals, microorganisms, pharmaceuticals and plastics,” Van Vleet says.

The analysis shows that in most cases water quality tends to deteriorate during drought and heat (68%), rain and floods (51%), as well as during long-term climate changes (56%). During droughts, less water is available to dilute pollutants, while rainstorms and floods cause more pollutants to flow from the ground into rivers and streams. In some cases, an improvement in water quality or a mixed response is also reported due to countermeasures such as increased pollutant transport being offset by greater dilution during floods.

Human impact and regional differences

Changes in water quality are largely caused by changes in river flow and water temperature. Other human factors such as land use and sewage treatment also affect this. “It is critical to understand the complex interactions between climate, land use, and human factors that together influence the sources and transport of pollutants,” says Van Vleet. The study also calls for additional data collection and water quality studies in non-Western countries. “We need better monitoring of water quality in Africa and Asia. “Most water quality research now focuses on rivers and streams in North America and Europe.”

The results of the study underscore the urgent need to better understand changes in water quality during extreme weather events and their underlying mechanisms. “Only then can we develop effective water management strategies that can protect our access to clean water and ensure ecosystem health in the face of climate change and increasing extreme weather.”