“Study reveals alarming impact of extreme weather on river water quality worldwide”
A new study published in the journal Nature Reviews Earth & Environment has revealed the alarming impact of extreme weather events on river water quality around the world. The study, conducted by an international team of researchers led by Utrecht University in the Netherlands, reviewed 965 studies to assess the effects of droughts, heatwaves, rainstorms, and flooding on rivers.
The researchers found that 68% of the case studies showed a deterioration in water quality under droughts, heatwaves, and compound drought-heatwave events. This deterioration was attributed to increased concentrations of pollutants and salinity in the rivers. Additionally, long-term climate change between 2000 and 2022 has led to rising water temperatures and algae levels in 56% of the case studies.
Various markers of water quality were analyzed in the study, including temperature, salinity, dissolved oxygen levels, algal blooms, and concentrations of nutrients, metals, microorganisms, pharmaceuticals, and plastics in river water. The researchers observed that droughts and heatwaves led to higher salinity levels and increased concentrations of pollutants, such as pharmaceuticals, while the surge in algae levels contributed to a decline in dissolved oxygen concentrations.
One striking example of the impact of extreme weather events on river water quality was the estimated five million fish deaths in the Darling River, Australia, between 2018 and 2019 due to low dissolved oxygen during a hydrological drought. The study also highlighted the projected increase in water temperature surges in regions such as the south-eastern USA, southern Europe, eastern Asia, and southern parts of Africa and Australia.
Furthermore, the researchers noted that rainstorms and floods also had a negative impact on river water quality, with 51% of the cases showing a deterioration. These events led to the accumulation of contaminants such as suspended sediments, plastics, nutrients, metals, and microorganisms in rivers and streams.
The study emphasized the importance of compiling local or regional water quality monitoring data into large datasets and using water quality models and techniques to prioritize streams and rivers for monitoring campaigns. While most of the rivers and streams analyzed in the study were from North America and Europe, there is a need for more comprehensive monitoring in regions such as Africa and parts of Asia.
Overall, the study underscores the urgent need to address the impact of extreme weather events on river water quality and to implement strategies to protect and preserve these vital water resources.