Drastic changes observed: global warming threatens water security in Europe

A group of scientists led by the University of Leeds (Great Britain) analyzed historical data from river measuring stations around the world and found that 21 percent they observed significant changes in the rise and fall of the seasonal water level, reports the Sci Tech Daily portal.

The study, based on reconstructions and recent simulations, showed that river flow at latitudes above 50 degrees north is now much less seasonal than before, and that this can be directly related to human-induced climate change.

Until now, evidence suggesting that climate change has affected the seasonality of river flows has been limited to local studies or has not explicitly considered the effects of human-induced climate change.

In this study, the team used measurements of the average monthly flow of rivers made between 1965 and 2014, from more than 10,000 measuring stations.

The changes were caused by climate change

For the first time in history, scientists have been able to rule out direct human intervention, such as water management or water extraction, and show that the widespread decrease in seasonality of river flows is caused by climate change.

The results of the study, which was funded by the University of Leeds and the South China University of Science and Technology, were recently published in the journal Science.

Lead author Hong Wang, a postdoctoral researcher at the University of Leeds and South China University of Science and Technology, said: “Our study shows that rising air temperatures are fundamentally changing the natural patterns of river flow.”

“It is alarming that the seasonality of river flows has been observed and that this is a direct consequence of historical human-caused emissions. This suggests that if the air temperature continues to rise, the seasonality of river flows will be permanently and significantly weakened,” he said.

Human impact on river flow

Human activities are changing the nature of river flows around the world, both directly through flow regulation such as reservoirs and indirectly through changes in land use and the effects of climate change on air temperature, precipitation, soil moisture and snowmelt.

More than two-thirds of the world’s rivers have already been altered by humans, not even considering the indirect effects of increasing greenhouse gases and aerosols.

The seasonality of river flow is very important for the predicted cycle of floods and droughts. The weakening of these peaks and tides can threaten water security and freshwater biodiversity. For example, much of the early meltwater can quickly drain into the oceans due to snowpack depletion, making it unavailable for human use.

Weakened river flow seasonality, for example due to reduced spring and early summer river level snowmelt in regions, can also affect riparian vegetation and riverine organisms.

Determination of seasonal flow

North American researchers found that 40 percent out of 119 monitored stations, a significant decrease in river flow seasonality was observed. Similar results were observed in southern Siberia – 32 percent. stations observed a significant decrease.

A similar pattern was observed in Europe – 19 percent. river gauging stations observed a significant decrease – mainly in Northern Europe, Western Russia and the European Alps.

In addition, regions of the contiguous United States, with the exception of the Rocky Mountain and Florida rivers, showed overall decreasing trends in river runoff seasonality.

Significant trends are observed

Studies conducted in Central North America showed that 18 percent stations, significant decreasing trends in river flow seasonality are observed.

Meanwhile, in southeastern Brazil, researchers found that 25 percent stations show a significant increase in the seasonality of river flow, indicating that changes in the water cycle have different effects in some parts of the world.

Dr Megan Klaar, Associate Professor in the School of Geography at the University of Leeds and a member of Water@leeds, co-authored the study, who said: “Seasonal fluctuations in river flow are vital for aquatic species. For example, many fish take advantage of a certain rise in water to run to their spawning grounds further up the stream or towards the sea. If she doesn’t have these signs, she won’t be able to spawn.”

It’s worth worrying about

The study concludes that there is a need to accelerate climate change adaptation efforts to protect freshwater ecosystems by managing flows and trying to restore some of the natural systems and processes that are being lost.

Professor Joseph Holden, director of Water@leeds, who led Hong Wan’s research, added: “There are many worries about what climate change will do in the future, but our study shows that it is already happening and that rising temperatures are causing huge changes in river flows “.

Mr Holden added: “We should be very concerned about what lies ahead in the face of accelerating climate change and start thinking about climate change mitigation strategies and adaptation planning to reduce seasonal river flows in the future, particularly in areas such as western Russia, Scandinavia and Canada’.