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Climate change is taking a significant toll on the quality of river water worldwide, posing threats to ecosystem health and human access to clean water, according to a recent study published in Nature Reviews Earth & Environment. The study, led by Dr. Michelle van Vliet of Utrecht University, sheds light on the impact of climate change-induced extreme weather events on river water quality.

The research team analyzed 965 cases of river water quality changes during various extreme weather conditions, including droughts, heatwaves, rainstorms, flooding, and long-term climate changes. Their findings revealed a troubling trend: river water quality tends to deteriorate after severe weather events.

"We looked at various water quality constituents such as water temperature, dissolved oxygen, salinity, and concentration of nutrients, metals, microorganisms, pharmaceuticals, and plastics," explained Dr. van Vliet.

The analysis showed that in most cases, water quality deteriorates during droughts and heatwaves (68%), rainstorms and floods (51%), and long-term climate changes (56%). During droughts, the limited availability of water makes it challenging to dilute contaminants. Conversely, rainstorms and floods often lead to more contaminants running off from land into rivers and streams.

While some cases reported improvements or mixed responses in water quality due to counteracting mechanisms, such as increased transport of pollutants offset by more dilution during flood events, the overall trend was concerning.

The study emphasized that changes in river discharge and water temperature, influenced by factors like land use and human activities such as wastewater treatment, play a significant role in driving changes in water quality. Understanding the complex interplay between climate, land use, and human drivers is crucial to addressing this issue effectively.

Furthermore, the research called for increased data collection and studies on 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," emphasized Dr. van Vliet.

In conclusion, the study highlights the urgent need for a better understanding of water quality changes during extreme weather events and the underlying mechanisms. Only with this knowledge can effective water management strategies be developed to safeguard access to clean water and ensure ecosystem health in the face of climate change and increasing weather extremes.